JP2006118886A - Distance calculation system, and distance calculation method for the distance calculation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distance calculation system and a distance calculation method for the distance calculation system, capable of surely calculating the distance between a first communications device and a second communication device to prevent unauthorized communication between the first communications device and the second communications device by a person other than the person concerned. <P>SOLUTION: In this distance calculation system for calculating the distance between a first communications device and a second communications device, the first communications device is provided with a transmission part for transmitting a distance calculating signal for calculating the distance with respect to the second communications device, a detection part for detecting the phase difference between the distance calculating signal when transmitted and the distance calculating signal when received, by receiving the distance calculating signal replied from the second communications device, and a calculation part for calculating the distance with respect to the second communications device, based on the phase difference detected by the detection part, and the second communications device is provided with a reply part for replying the distance calculating signal transmitted from the first communications device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a distance calculation system and a distance calculation method for the distance calculation system.

  In recent years, as communication devices that communicate with each other to execute predetermined processing, for example, there are an in-vehicle device and a portable device in an automobile equipped with a passive keyless entry system.

  Hereinafter, communication between an in-vehicle device and a portable device in an automobile equipped with a passive keyless entry system will be described in detail. The in-vehicle device is provided, for example, at a door on the driver's seat side of the automobile, and the portable device is possessed by the owner of the automobile (hereinafter referred to as a “carrier”). Then, it is assumed that the wearer stops the engine of the car, opens the door, and goes out of the car.

  The in-vehicle device transmits a signal (hereinafter referred to as signal A) for determining whether or not the portable device is within the communicable range (area) of the in-vehicle device and the portable device. When the carrier is within the communicable range, the portable device receives the signal A from the in-vehicle device and transmits a signal B corresponding to the signal A. When receiving the signal B from the portable device, the in-vehicle device determines that the portable device is within the communicable range. The transmission of the signal A from the in-vehicle device is repeatedly performed at a predetermined interval.

  If the carrier goes out of the communicable range, the portable device cannot receive the signal A from the in-vehicle device. Therefore, the in-vehicle device does not receive the signal B corresponding to the signal A from the portable device. For example, when the vehicle-mounted device does not receive the signal B from the portable device for a predetermined time, the vehicle-mounted device transmits an instruction signal for locking the door of the vehicle to a controller provided separately inside the vehicle. The control unit locks the door of the automobile based on the instruction signal from the in-vehicle device. Therefore, when the carrier leaves the automobile and the portable device is out of the communicable range, the door of the automobile is locked.

  Next, when the carrier who has once gone out of the communicable range returns to the communicable range again, the portable device receives the signal A from the in-vehicle device. Then, the portable device transmits the signal B. When receiving the signal B from the portable device, the in-vehicle device transmits, for example, a read signal for reading information of the portable device in order to determine whether the portable device is compatible with the vehicle. The portable device transmits portable device information based on the readout signal from the in-vehicle device. The in-vehicle device determines whether the portable device is compatible with the vehicle based on the portable device information from the portable device. When the in-vehicle device determines that the portable device is compatible with the vehicle, the vehicle-mounted device transmits an instruction signal for unlocking the door of the vehicle to the control unit described above. The control unit unlocks the door of the automobile based on the instruction signal from the in-vehicle device.

As described above, in a vehicle equipped with a passive keyless entry system, the vehicle door and the portable device communicate with each other without inserting the vehicle key into the keyhole, thereby locking or unlocking the door of the vehicle. It is possible to make it.
JP 2000-198420 A

  However, when a so-called relay attack is performed in the communication between the vehicle-mounted device and the portable device as described above of a vehicle equipped with a passive keyless entry system, the vehicle may be stolen. This relay attack means that even if the vehicle is originally out of the communicable range and communication between the in-vehicle device and the portable device becomes impossible, the in-vehicle device and the portable device are used by using the relay device. It refers to a thief that enables communication and steals the car by unlocking the door of the car.

  Hereinafter, the relay attack will be described in detail with reference to FIG. FIG. 12 is a diagram illustrating communication between the in-vehicle device 101 and the portable device 102 via the relay devices A and B. The in-vehicle device 101 is provided, for example, in a door on the driver's seat side and transmits the signal A described above. The in-vehicle device 101 can transmit and receive signals within the communication range indicated by the broken line C. When the portable device 102 receives the signal A from the in-vehicle device 101 as described above, the portable device 102 transmits the signal B corresponding to the signal A. Note that the portable device 102 can transmit and receive signals within the communication range indicated by the broken line D.

  When the carrier leaves the communicable range, the signal B corresponding to the signal A from the portable device 102 is not transmitted to the in-vehicle device 101 as described above, and the control unit (not shown) The door is locked based on the instruction signal.

  At this time, it is assumed that there are relayers X and Y trying to steal the car. The relay person X possesses the relay device A and puts the in-vehicle device 101 into the communication range C. In addition, the relay person Y possesses the relay machine B and goes to the side of the portable person, and puts the relay machine B within the communication range D of the portable machine 102. The repeater A possessed by the repeater X receives the signal A because it is within the communication range C of the in-vehicle device 101, and the repeater A detects the signal A, amplifies it, and transmits it. The repeater A amplifies the signal A so that the signal A can be transmitted in a wider range than the communication range C of the in-vehicle device 101. When the repeater B possessed by the repeater Y receives the signal A amplified by the repeater A, the repeater B detects the amplified signal A, for example, at a level before the repeater A amplifies. Attenuate to signal A and transmit. At this time, since the repeater B is within the communication range D of the portable device 102, the portable device 102 receives the signal A attenuated by the repeater B. The portable device 102 transmits a signal B corresponding to the signal A, assuming that the signal A from the in-vehicle device 101 has been transmitted. When the relay station B receives the signal B, the relay station B detects the signal B, amplifies it, and transmits it. The repeater B can amplify the signal B to transmit the signal B in a wider range than the communication range D of the portable device 102. When the repeater A receives the signal B amplified by the repeater B, the repeater A detects the amplified signal B and attenuates it to a signal B at a level before the repeater B amplifies, for example. Send. At this time, since the repeater A is within the communication range C of the in-vehicle device 101 as described above, the in-vehicle device 101 receives the signal B attenuated by the repeater A. Therefore, the in-vehicle device 101 determines that the portable device 102 is within the communicable range by receiving the signal B corresponding to the signal A. And the vehicle equipment 101 will perform the process mentioned above for unlocking the door of a motor vehicle. Then, for example, the relay person X gets into the unlocked car, and the car is stolen.

  As described above, in the communication between the in-vehicle device 101 and the portable device 102 with the relay devices A and B interposed therebetween, the in-vehicle device 101 can communicate with the portable device 102 by receiving the signal B through the relay devices A and B. There was a possibility of determining that it was within the range. Therefore, the in-vehicle device 101 transmits an instruction signal for unlocking the door of the automobile to the control unit, and the control unit may unlock the door even though the carrier is not within the communicable range. was there.

  Therefore, the present invention provides a communication between the first communication device and the second communication device in order to prevent unauthorized communication between the first communication device (for example, the in-vehicle device) and the second communication device (for example, the portable device). It is an object of the present invention to provide a distance calculation system capable of reliably calculating a distance and a distance calculation method of the distance calculation system.

  The invention for solving the above problem is a distance calculation system for calculating a distance between a first communication device and a second communication device, wherein the first communication device is connected to the second communication device. A transmission unit that transmits a distance calculation signal for calculating a distance, and the distance calculation signal sent back by receiving the distance calculation signal returned from the second communication device, and the received distance calculation signal A detection unit that detects a phase difference between the distance calculation signal and a calculation unit that calculates a distance from the second communication device based on the phase difference detected by the detection unit; , And the second communication device includes a reply unit that returns the distance calculation signal transmitted from the first communication device.

  Furthermore, it is the distance calculation method of the distance calculation system which calculates the distance between a 1st communication apparatus and a 2nd communication apparatus, Comprising: The said 1st communication apparatus calculates the distance between the said 2nd communication apparatuses. A distance calculation signal for transmitting, the second communication device returns the distance calculation signal transmitted from the first communication device, and the first communication device is returned from the second communication device. By receiving the distance calculation signal, a phase difference between the distance calculation signal when transmitted and the distance calculation signal when received is detected, and the second communication device is based on the phase difference The distance between is calculated.

  ADVANTAGE OF THE INVENTION According to this invention, the distance between a 1st communication apparatus and a 2nd communication apparatus can be calculated reliably, and the unauthorized communication by the party other than the party between a 1st communication apparatus and a 2nd communication apparatus is prevented reliably. It is possible to provide a distance calculation system and a distance calculation method for the distance calculation system.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

<< First Embodiment >>
=== Example of Overall Configuration of Distance Calculation System ===
The distance calculation system according to the present invention will be described with reference to FIG. FIG. 1 is a functional block diagram showing an example of the overall configuration of a distance calculation system according to the present invention.

  In the present embodiment, the distance calculation system will be described as being used for a passive keyless entry system that can lock or unlock a door of a car without operating a key, for example. The distance calculation system includes an in-vehicle device 1 (first communication device) and a portable device 2 (second communication device). It is assumed that the in-vehicle device 1 is provided, for example, on a door knob outside the driver's side door of an automobile, and the portable device 2 is provided, for example, on a key of the automobile.

  In the present embodiment, a low-frequency (for example, 125 kHz) carrier wave is used in signal communication from the in-vehicle device 1 to the portable device 2. Further, in the signal communication from the portable device 2 to the vehicle-mounted device 1, a high frequency (for example, 312 MHz) carrier wave is used. That is, in the communication from the in-vehicle device 1 to the portable device 2, the communication speed is slow because communication is performed with a low-frequency carrier wave. Conversely, in communication from the portable device 2 to the vehicle-mounted device 1, the communication speed is increased because communication is performed using a high-frequency carrier wave. The low frequency with low communication speed is used because the signal phase difference (time difference) between the time when the signal is transmitted from the vehicle-mounted device 1 and the time when the signal is returned via the portable device 2 as described later. This may be intentionally generated). Further, in the case of communication from the portable device 2 to the in-vehicle device 1, by using a high frequency with a high communication speed, the phase difference therebetween can be ignored compared to the phase difference generated during communication from the in-vehicle device 1 to the portable device 2. It will be about. That is, the distance between the in-vehicle device 1 and the portable device 2 can be calculated only with the phase difference intentionally generated in the communication from the in-vehicle device 1 to the portable device 2. Therefore, an intentional low frequency is used for communication from the in-vehicle device 1 to the portable device 2, and a higher frequency is used for communication from the portable device 2 to the in-vehicle device 1.

  Furthermore, in the communication from the vehicle-mounted device 1 to the portable device 2 as described above, communication is performed using a signal subjected to ASK modulation (amplitude shift keying). This is because a transmission unit 7 (transmission unit, first modulation unit) for transmitting a signal from the in-vehicle device 1 to the portable device 2 and a demodulation unit 24 (second demodulation) for receiving a signal from the in-vehicle device 1. This is because it is possible to transmit from the in-vehicle device 1 to the portable device 2 even if there is some interference. In communication from the portable device 2 to the in-vehicle device 1, communication is performed using a signal subjected to FSK modulation (Frequency Shift Keying). This is because a signal subjected to FSK modulation is not easily affected by noise, and can be reliably transmitted without loss of information from the portable device 2 to the in-vehicle device 1. In the present embodiment, communication is performed using an ASK-modulated signal in communication from the in-vehicle device 1 to the portable device 2, and communication is performed using an FSK-modulated signal in communication from the portable device 2 to the on-vehicle device 1. Yes, but not limited to this. For example, signal confidentiality can be enhanced, and communication from the in-vehicle device 1 to the portable device 2 and communication from the portable device 2 to the in-vehicle device 1 can be performed with a spread spectrum that has a remarkably high ability to eliminate interference waves and interference waves. It is also possible to do this.

  In the case of communication from the vehicle-mounted device 1 to the portable device 2, the use of the above-described low-frequency carrier wave makes use of a magnetic field component in which the intensity of electromagnetic waves is inversely proportional to the cube of the distance. Is about 1 m. On the other hand, in the case of communication from the portable device 2 to the vehicle-mounted device 1, the normal communication distance is 5 to 20 m by using the above-described high frequency carrier wave. Hereinafter, the communicable range between the in-vehicle device 1 and the portable device 2 is referred to as an area.

  The in-vehicle device 1 includes a CPU (Central Processing Unit) 3 (detection unit, calculation unit, determination unit, generation unit), counter 4, timer 5, Flash memory 6 (storage unit), transmission unit 7, reception unit 8 (first unit). A demodulation unit), a transmission antenna 9, a reception antenna 10, and an OSC 26 (oscillator circuit: Oscillator).

  The transmitter 7 performs ASK modulation on the signal from the CPU 3 with a carrier wave having a frequency of 125 kHz.

  The transmission antenna 9 transmits the signal subjected to ASK modulation by the transmission unit 7.

  The receiving antenna 10 receives an FSK modulated signal from the portable device 2.

  The receiving unit 8 demodulates the FSK-modulated signal from the portable device 2 received by the receiving antenna 10.

  The CPU 3 is provided for overall control of the in-vehicle device 1. The flash memory 6 stores in advance program data for the CPU 3 to perform processing to be described later. In addition, when the CPU 3 performs a process for unlocking the door of the automobile, the flash memory 6 has a code signal and personal data for collating with the data from the portable device 2 demodulated by the receiving unit 8. Stored in advance. Further, the flash memory 6 stores the encrypted personal data demodulated by the receiving unit 8 from the portable device 2 (the encryption stored in the flash memory 13 of the portable device 2 to be collated with the personal data described above by the CPU 3). An encryption / decryption program for decrypting the encrypted personal data) is stored in advance. The Flash memory 6 is composed of a nonvolatile memory element that can repeatedly write and read data by electrically erasing the data.

  The timer 5 measures time based on an instruction from the CPU 3.

  The OSC 26 transmits a clock (CLK0) having a predetermined frequency to the CPU 3.

  Based on an instruction from the CPU 3, the counter 4 starts from the rise of a signal (hereinafter referred to as a distance calculation signal) for calculating the distance from the in-vehicle device 1 to the portable device 2 transmitted from the CPU 3 to the transmission unit 7. For example, the rising edge of the clock from the OSC 26 is counted. The counter 4 counts the rising edge of the clock from the OSC 26 until the rising edge of the distance calculation signal demodulated by the receiving unit 8. The count value of the counter 4 is reset based on an instruction from the CPU 3.

  The CPU 3 transmits the above-described distance calculation signal to the transmission unit 7 and resets the counter 4 to start counting. Further, the CPU 3 resets the timer 5 to start measuring time. When receiving the distance calculation signal from the portable device 2 demodulated by the receiving unit 8, the CPU 3 reads the count value of the counter 4. The CPU 3 calculates the distance from the in-vehicle device 1 to the portable device 2 based on the count value. That is, the count value indicating the phase difference between the two signals from the time when the distance calculation signal is transmitted to the transmitter 7 to the time when the distance calculation signal is returned via the portable device 2 is obtained. The distance from the machine 1 to the portable machine 2 can be calculated. For example, when the frequency of the clock from the OSC 26 is 15.75 kHz, the count value of the counter 4 when the distance calculation signal is returned via the portable device 2 is 250. The phase difference is about 15.87 (msec). It is assumed that the distance from the vehicle-mounted device 1 to the portable device 2 when the phase difference is about 15.87 (msec) is about 1 (m), for example, from an experiment. The distance data corresponding to the count value obtained from this experiment is stored in advance in the Flash memory 6 as table data, for example. The CPU 3 determines whether or not the calculated distance is less than a predetermined distance (for example, 1 m). When the CPU 3 determines that the calculated distance is less than the predetermined distance described above, the CPU 3 sets a signal for making the inverter 21 (reply unit) of the portable device 2 inoperative (hereinafter referred to as an identification signal). ) To the transmitter 7. Further, the CPU 3 transmits a signal for reading a code signal corresponding to the code signal stored in the Flash memory 6 from the portable device 2 (hereinafter referred to as a code reading signal) to the transmission unit 7. The CPU 3 transmits the code signal from the portable device 2 demodulated by the receiving unit 8. When the CPU 3 determines that the code signal from the portable device 2 and the code signal from the flash memory 6 have a predetermined relationship, the CPU 3 reads the above-described signal for reading the encrypted personal data (hereinafter referred to as encrypted personal data). (Referred to as a read signal). The CPU 3 transmits the encrypted personal data from the portable device 2 demodulated by the receiving unit 8. The CPU 3 decrypts the encrypted personal data based on the decryption program stored in the Flash memory 6. If the CPU 3 determines that the decrypted personal data and the personal data from the Flash memory 6 match, it confirms which door of the car (for example, all the doors of the car or the door of the driver's seat) is to be unlocked. A signal (hereinafter referred to as an input confirmation signal) is transmitted to the transmitter 7. An input signal corresponding to the input confirmation signal from the portable device 2 demodulated by the receiving unit 8 is transmitted to the CPU 3. Based on the input signal from the portable device 2 demodulated by the receiving unit 8, the CPU 3 transmits an instruction signal for unlocking the door of the vehicle to a control unit (not shown) separately provided in the vehicle. . Further, the CPU 3 transmits a signal (hereinafter referred to as an in-area confirmation signal A) for determining whether or not the portable device 2 is within a communicable range to the transmission unit 7. At this time, the CPU 3 resets the timer 5 to start timing. The CPU 3 determines whether or not a signal corresponding to the in-area confirmation signal A (hereinafter referred to as an in-area confirmation signal B) is transmitted from the portable device 2 within a predetermined time (t1 in FIG. 4). Determine. If the CPU 3 determines that the in-area confirmation signal B is not transmitted from the portable device 2 within a predetermined time, the CPU 3 transmits an instruction signal for locking the door of the automobile to the control unit described above. Note that these functions of the CPU 3 are realized by the CPU 3 executing the program based on the result of decoding the program data read from the flash memory 6 described above. The CPU 3 includes an address counter (not shown) that specifies an address of the flash memory 6, a program logic array (not shown) that decodes program data read from the flash memory 6, an arithmetic logic unit (not shown) that performs logical operations, It has a register (not shown) for temporarily storing data.

  The portable device 2 includes a CPU 11 (switching unit), an input unit 12, a flash memory 13, a demodulation unit 24, a modulation unit 25 (second modulation unit), a reception antenna 18, a transmission antenna 19, inverters 20, 21, 22, and a flag 23. The timer 27 is provided.

  The receiving antenna 18 receives an ASK-modulated signal from the in-vehicle device 1.

  The demodulator 24 is composed of, for example, RF 16 (Radio Frequency) and DET 14 (Detector). The demodulator 24 demodulates the ASK-modulated signal from the receiving antenna 18.

  The modulation unit 25 includes, for example, an RF 17 and a modulator 15. The modulation unit 25 performs FSK modulation on the signal from the CPU 11 with a carrier wave having a frequency of 312 MHz. Further, the modulation unit 25 performs FSK modulation of the signal from the demodulation unit 24 with a carrier wave having a frequency of 312 MHz when the inverter 21 is in an operation state according to an instruction from the CPU 11.

  The transmission antenna 19 transmits the signal that has been FSK modulated by the modulation unit 25.

  The CPU 11 is provided for overall control of the portable device 2. The flash memory 13 stores in advance program data for the CPU 11 to perform processing to be described later. The flash memory 13 stores a code signal to be transmitted to the in-vehicle device 1 based on the code read signal from the in-vehicle device 1. Further, the flash memory 13 stores encrypted personal data to be transmitted to the in-vehicle device 1 based on the encrypted personal data read signal from the in-vehicle device 1. The flash memory 13 is composed of a nonvolatile memory element that can repeatedly write and read data by electrically erasing the data.

  The timer 27 measures time based on an instruction from the CPU 11.

  The input unit 12 receives an instruction signal based on an instruction input from, for example, a holder of the portable device 2 (hereinafter referred to as a “carrier”). For example, when the user wants to unlock the door on the driver's seat, the user inputs an instruction for unlocking the door on the driver's seat, and an instruction signal based on the instruction input is input to the input unit 12. When the instruction signal for unlocking the driver seat side door is input, the input unit 12 stores, for example, one logical value “1” in the flag 23. Further, for example, when the carrier wants to unlock all the doors of the automobile, the carrier inputs an instruction for unlocking all the doors of the automobile, and an instruction signal based on the instruction input is input to the input unit 12. The When the instruction signal for unlocking all the doors is input, the input unit 12 causes the flag 23 to store, for example, the other logical value “0”. In the present embodiment, for example, a changeover switch (not shown) is provided on a key, and when the wearer wants to unlock the door on the driver's seat, the changeover switch is switched to one side, If you want to unlock the door, switch the switch to the other side. An instruction signal for unlocking the door on the driver's seat side is input to the input unit 12 by switching the changeover switch to one side, and the input unit 12 is assumed to store “1” in the flag 23. To do. In addition, it is assumed that an instruction signal for unlocking all doors is input to the input unit 12 by switching the changeover switch to the other side, and the input unit 12 stores “0” in the flag 23.

  The CPU 11 transmits the in-area confirmation signal A from the in-vehicle device 1 demodulated by the demodulation unit 24 and transmits the in-area confirmation signal B to the modulation unit 25. At this time, the CPU 11 resets the timer 27 to start timing. The CPU 11 determines whether or not the in-area confirmation signal A is transmitted from the in-vehicle device 1 again within a predetermined time (FIG. 4, t2). When the CPU 11 determines that the in-area confirmation signal A is not transmitted within a predetermined time, the CPU 11 sets the inverter 21 in an operating state. Therefore, the signal from the in-vehicle device 1 demodulated by the demodulator 24 is FSK modulated by the modulator 25 as it is without being processed, and can be transmitted from the transmission antenna 19. When the CPU 11 determines that the identification signal transmitted from the in-vehicle device 1 demodulated by the demodulator 24 is transmitted, the CPU 11 puts the inverter 21 into an inoperative state. When the CPU 11 receives the code read signal from the in-vehicle device 1 demodulated by the demodulator 24 and determines that the code read signal has been transmitted, the CPU 11 reads the code signal from the flash memory 13 and transmits it to the modulator 25. . When the CPU 11 transmits the encrypted personal data read signal from the vehicle-mounted device 1 demodulated by the demodulator 24 and determines that the personal data read signal has been transmitted, the CPU 11 reads the encrypted personal data from the flash memory 13 and modulates it. To the unit 25. The CPU 11 transmits an input confirmation signal from the in-vehicle device 1 demodulated by the demodulator 24. Based on the input confirmation signal, the CPU 11 transmits information of “1” or “0” stored in the flag 23 at this time to the modulation unit 25 as an input signal. Note that these functions of the CPU 11 are realized by the CPU 11 executing the program based on the result of decoding the program data read from the flash memory 13 described above. The CPU 11 includes an address counter (not shown) that specifies an address of the flash memory 13, a program logic array (not shown) that decodes program data read from the flash memory 13, an arithmetic logic unit (not shown) that performs a logical operation, an arithmetic operation It has a register (not shown) for temporarily storing data.

=== Operation of distance calculation system (when no relay attack is performed) ===
The operation of the distance calculation system according to the present invention will be described with reference to FIGS. 2 and 3 are flowcharts showing an example of the operation of the distance calculation system according to the present invention. FIG. 4 is a timing chart showing an example of the operation of the distance calculation system according to the present invention. FIG. 5 is a diagram illustrating changes in the distance calculation signal. FIG. 4 shows that the signal described in the left column is transmitted when the level is high. In practice, the signal transmitted from the in-vehicle device 1 to the portable device 2 is an ASK-modulated signal in the transmission unit 7, and the signal transmitted from the portable device 2 to the in-vehicle device 1 is FSK modulated in the modulation unit 25. Signal. Further, for the sake of convenience, the description will be made assuming that one high level of the left column / vehicle equipment 1 distance calculation signal in FIG. 4 indicates the waveform of the left column / distance calculation signal (transmission) in FIG. Furthermore, in FIG. 4, all are the same rectangular wave (for example, portable device 2 code signal), but for the sake of convenience, the same rectangular wave is only shown and the present invention is not limited to this. For example, the portable device 2 code signal may be a code signal having code information corresponding to a high level period. By doing so, it becomes possible to transmit code information more effectively.

  In addition, in this embodiment, it demonstrates from the scene where a carrier stopped the engine of a motor vehicle, took out the motor vehicle with the portable device 2, and closed the door. Further, it is assumed that the inverter 21 of the portable device 2 is in an inoperative state.

  A controller (not shown) separately provided in the automobile receives a signal based on the fact that the door of the automobile is closed. A control part transmits the signal for starting a passive keyless entry system to CPU3 based on the said signal. Then, when receiving a signal for starting the passive keyless entry system, the CPU 3 transmits an in-area confirmation signal A to the transmission unit 7 (S101). At this time, the CPU 3 resets the timer 5. The reset timer 5 starts counting time. Then, the CPU 3 determines whether or not the in-area confirmation signal B demodulated by the receiving unit 8 from the portable device 2 is transmitted within a predetermined time (t1) (S102). The transmitter 7 ASK modulates the in-area confirmation signal A with a carrier wave having a frequency of 125 kHz. Then, the ASK-modulated in-area confirmation signal A from the transmission unit 7 is transmitted via the transmission antenna 9 (FIG. 4, in-vehicle device 1 in-area confirmation signal A).

  When the reception antenna 18 of the portable device 2 receives the ASK-modulated intra-area confirmation signal A, the demodulator 24 demodulates the ASK-modulated intra-area confirmation signal A. When the CPU 11 determines that the intra-area confirmation signal A demodulated by the demodulator 24 is transmitted (S201: YES), the CPU 11 transmits the intra-area confirmation signal B to the modulator 25 (S202). At this time, the CPU 11 resets the timer 27. The reset timer 27 starts counting time. Then, the CPU 11 determines whether or not the in-area confirmation signal A demodulated by the demodulator 24 is transmitted again within a predetermined time (t2) (S201). The modulation unit 25 performs FSK modulation of the in-area confirmation signal B from the CPU 11 with a carrier wave having a frequency of 312 MHz. The in-area confirmation signal B that has been FSK modulated by the modulator 25 is transmitted via the transmission antenna 19 (FIG. 4, portable device 2 in-area confirmation signal B).

  When the reception antenna 10 of the in-vehicle device 1 receives the FSK-modulated in-area confirmation signal B, the receiving unit 8 demodulates the FSK-modulated in-area confirmation signal B. When the CPU 3 determines that the in-area confirmation signal B from the portable device 2 demodulated by the receiving unit 8 has been transmitted (YES in S102), the CPU 3 transmits the in-area confirmation signal A to the transmitting unit 7 again (S101). ).

  In this way, if there is a carrier in the communicable range where the portable device 2 can receive the in-area confirmation signal A from the in-vehicle device 1, the in-vehicle device 1 may receive the in-area confirmation signal B from the portable device 2. It becomes possible (Fig. 4, in the area). Therefore, the vehicle-mounted device 1 can determine whether or not the carrier is in the vicinity (that is, within the communicable range).

  Next, the case where the carrier has left the above-described communicable range (FIG. 4, outside area) will be described.

  If the carrier leaves the communicable range, the portable device 2 cannot receive the in-area confirmation signal A from the in-vehicle device 1, and therefore the in-area confirmation signal B from the portable device 2 is not transmitted to the in-vehicle device 1. . If the CPU 3 determines that the in-area confirmation signal B is not transmitted from the portable device 2 even after a predetermined time (t1) has elapsed since the in-area confirmation signal A is transmitted (NO in S102), the vehicle An instruction signal for locking all the doors is transmitted to the control unit described above (S103, FIG. 4, door closed). In this case, the CPU 3 may be set to transmit the in-area confirmation signal A to the transmission unit 7 a plurality of times (for example, twice) (see FIG. 4). When the CPU 3 determines that the in-area confirmation signal B is not transmitted from the portable device 2 for any of the plurality of in-area confirmation signals A, it locks all the doors of the automobile. The instruction signal may be transmitted to the control unit. If it does so, CPU3 can discriminate | determine that a carrier is not in the communicable range more reliably. Furthermore, when the carrier once goes out of the communicable range but immediately returns to the communicable range, it is possible to eliminate the process for locking the door. Therefore, the time required for the process for unlocking the door is not necessary, and the delay of the time required for the process until the door is unlocked can be eliminated. Next, as described above, the CPU 3 determines that the in-area confirmation signal B from the portable device 2 has not been transmitted even after a predetermined time (t1) has elapsed since the in-area confirmation signal A was transmitted ( (S102, NO), a distance calculation signal (FIG. 5, distance calculation signal (transmission)) is transmitted to the transmitter 7 (S104). At this time, the CPU 3 resets the counter 4 and causes the counter 4 to start counting from the rising edge of the distance calculation signal. Further, the CPU 3 resets the timer 5 to start timing. Then, the CPU 3 determines whether or not the distance calculation signal is returned from the portable device 2 within a predetermined time (t3) (S105). The transmitter 7 ASK-modulates the distance calculation signal with a carrier wave having a frequency of 125 kHz (FIG. 5, ASK). The distance calculation signal ASK-modulated by the transmission unit 7 is transmitted via the transmission antenna 9 (FIG. 4, vehicle-mounted device 1 distance calculation signal). At this time, when the CPU 3 determines that the distance calculation signal demodulated by the receiving unit 8 is not returned within the predetermined time (t3) described above after transmitting the distance calculation signal, the distance calculation is performed again. Send a signal. Further, as described above, the timer 5 is reset to start timing, and the counter 5 is reset to start counting. The distance calculation signal is not limited to the waveform (distance calculation signal (transmission)) shown in FIG. In order to enhance security, for example, the content of the signal may be changed every time the CPU 3 transmits (that is, the waveform indicating the distance calculation signal changes), or the content of the signal may be changed at regular intervals.

  As described above, when the user goes out of the communicable range where the in-area confirmation signal A from the in-vehicle device 1 can be received, all the doors of the automobile are locked.

  When the CPU 11 determines that the in-area confirmation signal A is not transmitted for a predetermined period (t2), the CPU 11 sets the inverter 21 in the operating state (S203, FIG. 4, inverter 21).

  Next, the case where the carrier returns to the communicable range (in the area on the right in FIG. 4) will be described.

  When the carrier returns to the communicable range, the receiving antenna 18 of the portable device 2 receives the ASK-modulated distance calculation signal from the in-vehicle device 1. The demodulator 24 demodulates the ASK-modulated distance calculation signal. At this time, the distance calculation signal from the vehicle-mounted device 1 demodulated by the demodulator 24 is transmitted to the modulator 25 as it is because the inverter 21 is in an operating state (S205). The modulation unit 25 performs FSK modulation on the distance calculation signal from the demodulation unit 24 with a carrier wave having a frequency of 312 MHz (FIG. 5, FSK). The distance calculation signal that has been FSK modulated by the modulation unit 25 is transmitted via the transmission antenna 19 (FIG. 4, portable device 2 distance calculation signal).

  When the receiving antenna 10 of the vehicle-mounted device 1 receives the FSK-modulated distance calculation signal, the receiving unit 8 demodulates the FSK-modulated distance calculation signal (FIG. 5, distance calculation signal (reception)). When the CPU 3 determines that the distance calculation signal from the portable device 2 demodulated by the receiving unit 8 is transmitted (YES in S105), the CPU 3 reads the count value of the counter 4. Based on the count value, the distance from the in-vehicle device 1 to the portable device 2 is calculated (S106). As described above, in communication from the in-vehicle device 1 to the portable device 2, a low-frequency 125 kHz carrier wave is used. In communication from the portable device 2 to the vehicle-mounted device 1, a carrier wave of 312 MHz, which is a high frequency, is used. Therefore, the phase difference in communication from the portable device 2 to the in-vehicle device 1 is negligible compared to the phase difference generated during communication from the in-vehicle device 1 to the portable device 2. Therefore, an intentional phase difference T1 (FIG. 5) is generated between the distance calculation signal transmitted from the CPU 3 to the transmission unit 7 and the distance calculation signal demodulated by the reception unit 8 by using a low frequency of 125 kHz. It will be. Therefore, the count value read by the CPU 3 described above indicates the phase difference T1. Then, the CPU 3 reads the distance corresponding to the count value obtained from the experiment stored as table data in the Flash memory 6. Therefore, the CPU 3 can calculate the distance from the in-vehicle device 1 to the portable device 2 using the count value indicating the phase difference T1. Then, the CPU 3 determines whether or not the portable device 2 is less than a predetermined distance (for example, 1 m) from the in-vehicle device 1 (S108). In the present embodiment, whether or not the distance from the in-vehicle device 1 to the portable device 2 is less than a predetermined distance is determined based on the count value of the counter 4, but is not limited thereto. For example, when the CPU 3 causes the transmission unit 7 to transmit a distance calculation signal from the CPU 3, the timer 5 measures the time, and when the distance calculation signal from the portable device 2 demodulated by the reception unit 8 is transmitted. Read the time counted by the timer 5. It is also possible to determine whether or not the distance from the in-vehicle device 1 to the portable device 2 is less than a predetermined distance using the time measured by the timer 5. Further, the determination of the distance from the in-vehicle device 1 to the portable device 2 by the CPU 3 is not limited to one time. For example, when the distance from the in-vehicle device 1 to the portable device 2 is determined a plurality of times (three times in FIG. 4) and it is determined that the distance is less than a predetermined distance in all the determinations, The CPU 3 may proceed to the process. By doing so, it becomes possible to determine the distance from the in-vehicle device 1 to the portable device 2 more reliably. When the CPU 3 determines that the calculated distance from the in-vehicle device 1 to the portable device 2 is less than a predetermined distance (YES in S108), the CPU 3 transmits an identification signal to the transmission unit 7 (S109). The transmitter 7 ASK modulates the identification signal with a carrier wave having a frequency of 125 kHz. Then, the ASK-modulated identification signal from the transmission unit 7 is transmitted via the transmission antenna 9 (FIG. 4, vehicle-mounted device 1 identification signal).

  When the reception antenna 18 of the portable device 2 receives the ASK-modulated identification signal, the demodulator 24 demodulates the ASK-modulated identification signal. When the CPU 11 determines that the identification signal demodulated by the demodulator 24 is transmitted from the vehicle-mounted device 1 (YES in S206), it makes the inverter 21 inoperative (S207, FIG. 4, inverter 21).

  Next, the CPU 3 of the in-vehicle device 1 transmits a code reading signal to the transmission unit 7 (S110). Then, the CPU 3 determines whether or not the code signal from the portable device 2 demodulated by the receiving unit 8 is transmitted (S111). The transmitter 7 ASK modulates the code read signal with a carrier wave having a frequency of 125 kHz. Then, the ASK-modulated code read signal from the transmission unit 7 is transmitted through the transmission antenna 9 (FIG. 4, onboard unit 1 code read signal).

  When the receiving antenna 18 of the portable device 2 receives the ASK modulated code read signal, the demodulator 24 demodulates the ASK modulated code read signal. When determining that the code read signal from the vehicle-mounted device 1 demodulated by the demodulator 24 is transmitted (YES in S208), the CPU 11 reads the code signal from the flash memory 13. Then, the CPU 11 transmits the code signal to the modulation unit 25 (S209). The modulation unit 25 performs FSK modulation of the code signal from the CPU 11 with a carrier wave having a frequency of 312 MHz. The code signal subjected to FSK modulation by the modulation unit 25 is transmitted via the transmission antenna 19 (FIG. 4, portable device 2 code signal).

  When the receiving antenna 10 of the vehicle-mounted device 1 receives the FSK modulated code signal, the receiving unit 8 demodulates the FSK modulated code signal. When the CPU 3 determines that the code signal from the portable device 2 demodulated by the receiving unit 8 has been transmitted (YES in S111), the CPU 3 sends the code signal from the flash memory 6 to be compared with the code signal from the portable device 2. read out. Then, the CPU 3 determines whether or not the code signal from the portable device 2 and the code signal from the Flash memory 6 have a predetermined relationship (S112). When the CPU 3 determines that the code signal from the portable device 2 and the code signal from the flash memory 6 have a predetermined relationship (YES in S112), the CPU 3 transmits the encrypted personal data read signal to the transmission unit 7. (S113). Then, the CPU 3 determines whether or not the encrypted personal data demodulated by the receiving unit 8 is transmitted from the portable device 2 (S114). The transmitter 7 ASK modulates the encrypted personal data read signal with a carrier wave having a frequency of 125 kHz. Then, the ASK-modulated encrypted personal data read signal from the transmitter 7 is transmitted via the transmission antenna 9 (FIG. 4, on-vehicle device 1 encrypted personal data read signal).

  When the receiving antenna 18 of the portable device 2 receives the ASK-modulated encrypted personal data read signal, the demodulator 24 demodulates the ASK-modulated encrypted personal data read signal. When the CPU 11 determines that the encrypted personal data read signal demodulated by the demodulator 24 has been transmitted (YES in S210), the CPU 11 reads the encrypted personal data from the Flash memory 13. Then, the CPU 11 transmits the encrypted personal data to the modulation unit 25 (S211). The modulation unit 25 performs FSK modulation of the encrypted personal data from the CPU 11 with a carrier wave having a frequency of 312 MHz. The encrypted personal data that has been FSK modulated by the modulator 25 is transmitted via the transmission antenna 19 (FIG. 4, portable device 2 encrypted personal data).

  When the receiving antenna 10 of the vehicle-mounted device 1 receives the FSK-modulated encrypted personal data, the receiving unit 8 demodulates the FSK-modulated encrypted personal data. When the CPU 3 determines that the encrypted personal data demodulated by the receiving unit 8 is transmitted from the portable device 2 (YES in S114), the CPU 3 determines, based on the decryption program stored in the Flash memory 6, The encrypted personal data is decrypted (S115). When the decryption of the encrypted personal data from the portable device 2 is completed (hereinafter, the decrypted encrypted personal data is referred to as the decrypted personal data), the CPU 3 reads the personal data stored in the flash memory 6. The CPU 3 determines whether or not the decrypted personal data matches the personal data from the Flash memory 6 (S116). If the CPU 3 determines that the decrypted personal data matches the personal data from the Flash memory 6 (YES in S116), the CPU 3 transmits an input confirmation signal to the transmitter 7 (S117). Then, the CPU 3 determines whether or not the input signal from the portable device 2 demodulated by the receiving unit 8 is transmitted (S118). The transmitter 7 ASK modulates the input confirmation signal with a carrier wave having a frequency of 125 kHz. Then, the ASK-modulated input confirmation signal from the transmission unit 7 is transmitted via the transmission antenna 9 (FIG. 4, in-vehicle device 1 input confirmation signal).

  When the receiving antenna 18 of the portable device 2 receives the ASK modulated input confirmation signal, the demodulator 24 demodulates the ASK modulated input confirmation signal. When the CPU 11 determines that the input confirmation signal demodulated by the demodulator 24 has been transmitted (YES in S212), the CPU 11 reads the information stored in the flag 23. The information stored in the flag 23 at this time is an instruction signal by switching the changeover switch (not shown) to one side when the carrier wants to unlock the door on the driver's seat as described above. Is input to the input unit 12, and the information “1” stored in the flag 23 by the input unit 12 based on the instruction signal. Alternatively, as described above, when the carrier wants to unlock all the doors of the automobile, the carrier switches the changeover switch (not shown) to the other side so that the instruction signal is inputted to the input unit 12 and the input unit 12 Information “0” stored in the flag 23 based on the instruction signal. In the present embodiment, the following description will be made assuming that “1” is stored in the flag 23, for example. The CPU 11 transmits an input signal corresponding to “1” stored in the flag 23 to the modulation unit 25 (S213). The modulation unit 25 performs FSK modulation of the input signal from the CPU 11 with a carrier wave having a frequency of 312 MHz. The input signal that has been FSK modulated by the modulation unit 25 is transmitted via the transmission antenna 19 (FIG. 4, portable device 2 input signal).

  When the receiving antenna 10 of the vehicle-mounted device 1 receives the FSK-modulated input signal, the receiving unit 8 demodulates the FSK-modulated input signal. When the CPU 3 determines that the input signal from the portable device 2 demodulated by the receiving unit 8 has been transmitted (YES in S118), the CPU 3 determines whether or not the input signal is an input signal corresponding to “1”. It discriminate | determines (S119). When the CPU 3 determines that the input signal is an input signal corresponding to “1” (YES in S119), the control unit (not shown) is used to unlock only the door on the driver's side of the automobile. ) Is transmitted (S120). If the CPU 3 determines that the input signal is not an input signal corresponding to “1” (NO in S119), the CPU 3 transmits an instruction signal to the control unit described above to unlock all the doors of the automobile (S121).

  In this way, the portable device 2 is within the communicable range, and the distance calculation signal transmitted from the CPU 3 to the transmission unit 7 and the distance calculation signal from the portable device 2 demodulated by the reception unit 8 are mounted on the vehicle. When the distance from the device 1 to the portable device 2 is calculated and it is determined that the distance is less than a predetermined distance, all the doors of the automobile or the doors of the driver's seat are unlocked by the control unit.

=== Operation of distance calculation system (when relay attack is performed) ===
The operation of the distance calculation system according to the present invention when the above-described relay attack is performed will be described with reference to FIGS. 1 to 3, 6, and 7. FIG. 6 is a timing chart showing an example of the operation of the distance calculation system according to the present invention. FIG. 7 is a diagram illustrating changes in the distance calculation signal. Note that FIG. 6 shows that the signal described in the left column is transmitted when the level is high, for convenience, as in FIG. 4 described above. In practice, the signal transmitted from the in-vehicle device 1 to the portable device 2 is an ASK-modulated signal in the transmission unit 7, and the signal transmitted from the portable device 2 to the in-vehicle device 1 is FSK modulated in the modulation unit 25. Signal. Further, for the sake of convenience, the description of the left column / in-vehicle device 1 distance calculation signal high level in FIG. 6 indicates the waveform of the left column / distance calculation signal (transmission) in FIG. In the present embodiment, the explanation will be made from the scene in which the user stops the engine of the automobile, leaves the automobile with the portable device 2 and closes the door. Further, it is assumed that the inverter 21 of the portable device 2 is in an inoperative state.

  Furthermore, this embodiment can communicate with the owner (hereinafter referred to as “relayer X”) of the relay device A (not shown) in the communication range of the in-vehicle device 1 and the above-described relay device A in the communication range of the portable device 2. A case where a relay attack is performed by the owner (hereinafter referred to as a relay person Y) of the relay machine B (not shown) will be described.

  When the carrier is within the communicable range, it is the same as the case where there is no relay attack described above.

  If the carrier leaves the communicable range, the portable device 2 cannot receive the in-area confirmation signal A from the in-vehicle device 1, and therefore the in-area confirmation signal B from the portable device 2 is not transmitted to the in-vehicle device 1. . Therefore, the CPU 3 determines that the in-area confirmation signal B from the portable device 2 is not transmitted even after a predetermined time (t1) has elapsed since the in-area confirmation signal A was transmitted (NO in S102). And CPU3 transmits the instruction | indication signal for locking all the doors of a motor vehicle to the control part (not shown) separately provided in the motor vehicle (S103. FIG. 6, door closing). Note that, as described in the case where there is no relay attack, the CPU 3 may be set to transmit the in-area confirmation signal A to the transmitter 7 a plurality of times (for example, twice) (see FIG. 6). The CPU 3 transmits the above-described instruction signal to the control unit and transmits a distance calculation signal (FIG. 7, distance calculation signal (transmission)) to the transmission unit 7. At this time, the CPU 3 resets the counter 4 and causes the counter 4 to start counting from the rising edge of the distance calculation signal. Further, the CPU 3 resets the timer 5 to start timing. Then, the CPU 3 determines whether or not the distance calculation signal is returned from the portable device 2 within a predetermined time (t3) (S105). The transmitter 7 ASK-modulates the distance calculation signal with a carrier wave having a frequency of 125 kHz (FIG. 7, ASK (1)). Then, the distance calculation signal ASK (1) ASK-modulated by the transmission unit 7 is transmitted via the transmission antenna 9 (FIG. 6, vehicle-mounted device 1 distance calculation signal). At this time, when the CPU 3 determines that the distance calculation signal demodulated by the receiving unit 8 is not returned within the predetermined time (t3) described above after transmitting the distance calculation signal, the distance calculation is performed again. Send a signal. Further, as described above, the timer 5 is reset to start timing, and the counter 5 is reset to start counting.

  As described above, when the user goes out of the communicable range where the in-area confirmation signal A from the in-vehicle device 1 can be received, all the doors of the automobile are locked.

  When the CPU 11 determines that the in-area confirmation signal A is not transmitted for a predetermined period (t2), the CPU 11 sets the inverter 21 in an operating state (S203, FIG. 6, inverter 21).

  For example, when the carrier leaves the communicable range and moves away to a distance where the vehicle cannot be visually recognized, the relay person X goes near the vehicle so that the relay device A enters the communication range of the in-vehicle device 1. Further, it is assumed that the relay person Y approaches the mobile phone person and tries to steal the car by causing the relay machine B to enter the communication range of the mobile device 2 (relay attack is performed).

  When receiving the distance calculation signal from the in-vehicle device 1, the repeater A within the communication range of the in-vehicle device 1 detects and amplifies the distance calculation signal (FIG. 7, ASK (2)). Then, the relay A transmits a distance calculation signal ASK (2). At this time, the communication distance of the distance calculation signal ASK (2) transmitted from the repeater A is amplified by the repeater A compared to the normal communication distance of the distance calculation signal ASK (1) from the in-vehicle device 1. Therefore, communication over a longer distance is possible. Note that the communication distance of the distance calculation signal ASK (2) at this time will be described below assuming that it is a distance that the repeater B can receive.

  When the repeater B receives the distance calculation signal ASK (2) from the repeater A, the repeater B detects the distance calculation signal ASK (2), for example, up to the level of the distance calculation signal transmitted by the in-vehicle device 1. Attenuates. Then, the repeater B transmits the attenuated distance calculation signal ASK (3).

  At this time, since the repeater Y is near the carrier as described above, the repeater B is in the communication range of the portable device 2, so that the receiving antenna 18 receives the distance calculation signal ASK (3). To do. The demodulator 24 demodulates the distance calculation signal ASK (3). At this time, the distance calculation signal from the repeater B demodulated by the demodulator 24 is transmitted to the modulator 25 as it is because the inverter 21 is in an operating state (S205). The modulation unit 25 performs FSK modulation of the distance calculation signal from the demodulation unit 24 with a carrier wave having a frequency of 312 MHz (FIG. 5, FSK (1)). The distance calculation signal FSK (1) FSK-modulated by the modulation unit 25 is transmitted through the transmission antenna 19 (FIG. 6, portable device 2 distance calculation signal).

  Since the repeater 2 is within the communication range of the portable device 2 as described above, the repeater B receives the FSK-modulated distance calculation signal FSK (1) from the portable device 2. The repeater B detects and amplifies the FSK-modulated distance calculation signal FSK (1) (FIG. 7, FSK (2)). Then, the relay station B transmits a distance calculation signal FSK (2). At this time, the communication distance of the distance calculation signal FSK (2) transmitted from the repeater B is amplified by the repeater B compared to the normal communication distance of the distance calculation signal FSK (1) from the portable device 2. Therefore, communication over a longer distance is possible. Note that the communication distance of the distance calculation signal FSK (2) at this time will be described below assuming that it is a distance that the repeater A can receive.

  When the relay device A receives the distance calculation signal FSK (2) from the relay device B, the relay device A detects the distance calculation signal FSK (2), for example, to the level of the distance calculation signal transmitted by the portable device 2. Attenuates. Then, the repeater A transmits the attenuated distance calculation signal FSK (3).

  At this time, since the relay person X is near the vehicle as described above, the relay apparatus A is in the communication range of the in-vehicle apparatus 1, and therefore the receiving antenna 10 receives the distance calculation signal FSK (3). . The receiving unit 8 demodulates the distance calculation signal FSK (3) (FIG. 7, distance calculation signal (reception)). When the CPU 3 determines that the distance calculation signal demodulated by the receiving unit 8 has been transmitted (YES in S105), the CPU 3 reads the count value of the counter 4. Based on the count value, the distance from the in-vehicle device 1 to the portable device 2 is calculated (S106).

  The calculation method of the distance from the vehicle-mounted device 1 to the portable device 2 by the CPU 3 at this time is the same as the case where there is no relay attack described above. However, as described above, the repeater A amplifies the distance calculation signal ASK (1) transmitted from the in-vehicle device 1 and transmits the distance calculation signal ASK (2). At this time, in order to amplify the distance calculation signal ASK (1), the repeater A must first detect the distance calculation signal ASK (1) and then perform amplification. Furthermore, as described above, in communication from the in-vehicle device 1 to the portable device 2, communication is performed by ASK modulation with a low-frequency carrier of 125 kHz. Therefore, one cycle of the distance calculation signal ASK (1) is longer than the distance calculation signal FSK (1) transmitted from the portable device 2. In other words, since the repeater A detects and amplifies the distance calculation signal ASK (1) having a long cycle once, the phase difference T2 between the distance calculation signal ASK (1) and the distance calculation signal ASK (2). Will occur. Further, in the attenuation of the distance calculation signal ASK (2) to the distance calculation signal ASK (3) in the repeater 2, the phase difference T3 due to the above-described reason also occurs. That is, the phase difference between the distance calculation signal (transmission) transmitted from the CPU 3 to the transmission unit 7 and the distance calculation signal (reception) demodulated by the reception unit 8 is T4 (T2 + T3). The count value of the counter 4 read by the CPU 3 indicates the phase difference T4. Using the count value indicating the phase difference T4, the CPU 3 calculates the distance from the in-vehicle device 1 to the portable device 2. At this time, the count value indicating the phase difference T4 used by the CPU 3 to calculate the distance from the in-vehicle device 1 to the portable device 2 is the phase difference T1 when there is no relay attack in which the relay devices A and B are not interposed (FIG. 5). ) Is larger than the count value indicating). That is, the distance from the in-vehicle device 1 to the portable device 2 calculated based on the count value indicating the phase difference T4 by the CPU 3 is longer than the distance calculated based on the count value indicating the phase difference T1.

  Then, the CPU 3 determines whether or not the portable device 2 is less than a predetermined distance from the in-vehicle device 1 based on the calculated distance (S108). However, since the distance calculated by the CPU 3 is longer than the distance calculated when there is no relay attack as described above, the CPU 3 determines that the distance is not less than a predetermined distance (S108 • NO). At that time, the CPU 3 determines whether or not the time measured by the timer 5 has reached a predetermined time (t4) (S122).

  When it is determined that the predetermined time (t4) has not been reached (S122, NO), the CPU 3 transmits the distance calculation signal to the transmission unit 7 again (FIG. 7, right side of the distance calculation signal (transmission)). At this time, the CPU 3 resets the counter 4 and causes the counter 4 to start counting from the rising edge of the distance calculation signal. The reason why the CPU 3 transmits the distance calculation signal to the transmission unit 7 again is to make the calculation of the distance from the in-vehicle device 1 to the portable device 2 by the CPU 3 more reliable. If the CPU 3 determines that the predetermined time (t4) has been reached without determining that the distance is less than the predetermined distance (NO at S108), the CPU 3 stops communication with the portable device 2 (YES at S122). S123). In the present embodiment, when the CPU 3 determines that the distance is not less than a predetermined distance, the communication with the portable device 2 is stopped, but the present invention is not limited to this. For example, an alarm unit (not shown) for issuing an alarm to the portable device 2 is provided. When the CPU 3 determines that the distance is not less than the predetermined distance, the CPU 3 transmits an alarm signal for the alarm unit to issue an alarm to the transmission unit 7. And based on the said warning signal transmitted to the portable device 2 via the relay machines A and B, you may make it an alarm part emit a warning. By doing so, the carrier can know that the relayers X and Y are present, and the security can be improved.

  As described above, when relay attack is performed, the phase difference of the distance calculation signal is increased by the relay A and the relay B being interposed in the communication from the in-vehicle device 1 to the portable device 2 as described above. For this reason, the CPU 3 determines that the portable device 2 is not less than a predetermined distance from the in-vehicle device 1, and stops communication with the portable device 2 when a predetermined time (t4) is reached. Therefore, the car door is not unlocked by the relay attack of the relay persons X and Y, and the car can be prevented from being stolen.

  Even if the carrier returns to the communicable range again, the door is not unlocked because the vehicle-mounted device 1 stops communication with the portable device 2 as described above. In this case, the carrier unlocks the door by inserting the key into the keyhole. At that time, a control unit (not shown) receives a signal based on the door being unlocked due to the key being inserted into the keyhole. Based on the signal, the control unit transmits to the CPU 3 a communication start signal for the in-vehicle device 1 to start communication with the portable device 2. When the CPU 3 receives the communication start signal (S124, YES), it starts communication with the portable device 2 again.

<< Second Embodiment >>
=== Overall Configuration of Distance Calculation System ===
The distance calculation system according to the present invention will be described with reference to FIGS. FIG. 8 is a functional block diagram showing an example of the overall configuration of the distance calculation system according to the present invention. In the present embodiment, four in-vehicle devices 1 of the distance calculation system in the first embodiment are provided in the vehicle (on-vehicle devices 1A, 1B, 1C, and 1D), and the portable device 2 somewhere in the vehicle A case where a distance calculation system is used for detection will be described. Therefore, the distance calculation system is composed of the in-vehicle devices 1A, 1B, 1C, 1D, the portable device 2, and the CPU 90. Also, in FIG. 8, the same components as those in FIG. 1 described above are denoted by the same reference numerals and description thereof is omitted. Further, in FIG. 8, the in-vehicle devices 1 </ b> A, 1 </ b> B, 1 </ b> C, and 1 </ b> D have the same configuration as that of the in-vehicle device 1 in FIG. 1. FIG. 10 is a diagram illustrating detection of the portable device 2 by the in-vehicle devices 1A, 1B, 1C, and 1D. If the + X direction in FIG. 10 is the front direction of the vehicle, for example, the in-vehicle device 1A is provided on the front left side, the in-vehicle device 1B is provided on the front right side, and the in-vehicle device 1C is provided on the rear left side. Is provided on the rear right side. Moreover, CPU90 shall be provided in the motor vehicle provided with vehicle equipment 1A, 1B, 1C, 1D. It is assumed that the portable device 2 is provided on a car key.

  The CPU 90 performs overall control of the in-vehicle devices 1A, 1B, 1C, and 1D.

  The in-vehicle device 1A includes a CPU 3A, a counter 4A, a timer 5A, a flash memory 6A, a transmission unit 7A, a reception unit 8A, a transmission antenna 9A, a reception antenna 10A, and an OSC 26A.

  Based on the instruction signal from the CPU 90, the CPU 3A transmits a signal (hereinafter referred to as an in-vehicle confirmation signal A) for confirming whether or not the portable device 2 is in the automobile to the transmission unit 7A. The CPU 3A transmits the in-vehicle confirmation signal B from the portable device 2 demodulated by the receiving unit 8A. The CPU 3A transmits a signal (hereinafter referred to as a confirmation signal) based on the transmission of the in-vehicle confirmation signal B to the CPU 90. The CPU 3A transmits a signal (hereinafter referred to as an unconfirmed signal) based on the fact that the in-vehicle confirmation signal B has not been transmitted to the CPU 90. The CPU 3A transmits a signal (hereinafter referred to as an inverter operation instruction signal) for setting the inverter 21 to an operation state based on the instruction signal from the CPU 90 to the transmission unit 7A. The CPU 3A transmits a signal (hereinafter referred to as an inverter non-operation instruction signal) for making the inverter 21 non-operational to the transmission unit 7A. Further, the CPU 3A calculates the distance from the in-vehicle device 1A to the portable device 2 based on the count value of the counter 4A as in the first embodiment. The CPU 3A transmits the calculated distance information from the in-vehicle device 1A to the portable device 2 to the CPU 90.

  The configuration of the in-vehicle devices 1B, 1C, and 1D is the same as that of the in-vehicle device 1A described above. The vehicle-mounted devices 1A, 1B, 1C, and 1D may simultaneously perform the above-described processing based on an instruction from the CPU 90, or may sequentially perform the above-described processing.

  Based on an instruction signal from a control unit (not shown) provided in the automobile, the CPU 90 transmits an instruction signal for the CPU 3A, 3B, 3C, 3D to transmit the above-described in-vehicle confirmation signal A. Send to 1C, 1D. The CPU 90 transmits a signal for permitting the engine start of the vehicle (hereinafter referred to as an engine start permission signal) to the control unit based on the above-described confirmation signals from the in-vehicle devices 1A, 1B, 1C, and 1D. Further, the CPU 90 transmits a signal for not permitting the engine start of the vehicle (hereinafter referred to as an engine start non-permission signal) to the control unit based on the above-described unconfirmed signals from the in-vehicle devices 1A, 1B, 1C, and 1D. . The CPU 90 transmits a signal (hereinafter referred to as a detection signal) for detecting the portable device 2 from the control unit. Based on the detection signal, the CPU 90 transmits an instruction signal for the CPU 3A, 3B, 3C, 3D to transmit the inverter operation instruction signal described above to the in-vehicle devices 1A, 1B, 1C, 1D. And CPU90 transmits the instruction | indication signal for making CPU3A, 3B, 3C, 3D calculate the distance from vehicle equipment 1A, 1B, 1C, 1D to the portable device 2 to vehicle equipment 1A, 1B, 1C, 1D. The CPU 90 transmits distance information from the in-vehicle devices 1A, 1B, 1C, 1D to the portable device 2 calculated by the CPUs 3A, 3B, 3C, 3D. The CPU 90 calculates where the portable device 2 is in the vehicle based on the distance information calculated by the CPUs 3A, 3B, 3C, and 3D. In calculating the location where the portable device 2 is located, the CPU 90 reads program data for calculating the location where the portable device 2 is stored, which is stored in a memory (not shown). Then, in the arithmetic processing of the program by the CPU 90, the location where the portable device 2 is located can be calculated by using the coincidence point of each distance read from the distance information from the in-vehicle devices 1A, 1B, 1C, 1D. For example, the distance to the portable device 2 calculated by the vehicle-mounted device 1A is 120 cm, the distance to the portable device 2 calculated by the vehicle-mounted device 1B is 212 cm, the distance to the portable device 2 calculated by the vehicle-mounted device 1C is 20 cm, and the vehicle-mounted device 1D. Assume that the distance from the mobile device 2 to the portable device 2 is 117 cm. At that time, the CPU 90 has a point where the distance from the vehicle-mounted device 1A is 120 cm, a point where the distance from the vehicle-mounted device 1B is 212 cm, a point where the distance from the vehicle-mounted device 1C is 20 cm, and a point from the vehicle-mounted device 1D. A point at which the distance of 117 cm coincides is calculated, and it is determined that the portable device 2 is on the coincidence point.

  The portable device 2 includes a CPU 11, a Flash memory 13, a demodulation unit 24, a modulation unit 25, a reception antenna 18, a transmission antenna 19, and inverters 20, 21, and 22.

  The CPU 11 transmits an in-vehicle confirmation signal A from the in-vehicle devices 1A, 1B, 1C, 1D demodulated by the demodulator 24. Based on the vehicle interior confirmation signal A, the CPU 11 transmits the vehicle interior confirmation signal B to the modulation unit 25. The CPU 11 transmits inverter operation instruction signals from the vehicle-mounted devices 1A, 1B, 1C, and 1D demodulated by the demodulator 24. The CPU 11 puts the inverter 21 into an operating state based on the inverter operation instruction signal. Therefore, no processing is performed on the signals from the vehicle-mounted devices 1A, 1B, 1C, and 1D demodulated by the demodulator 24, and the signals are directly FSK modulated by the modulator 25 and transmitted from the transmission antenna 19. It becomes possible. The CPU 11 transmits the inverter non-operation instruction signal from the vehicle-mounted devices 1A, 1B, 1C, and 1D demodulated by the demodulator 24, and makes the inverter 21 non-operation based on the inverter non-operation instruction signal.

=== Operation of Distance Calculation System ===
The operation of the distance calculation system according to the present invention will be described with reference to FIGS. FIG. 9 is a flowchart showing an example of the operation of the distance calculation system according to the present invention. FIG. 11 is a diagram illustrating an example of the display screen of the monitor 92.

  In this embodiment, the carrier unlocks the door of the automobile, gets into the automobile, places the portable device 2 somewhere in the automobile, and forgets where the portable person places the portable device 2. The case where it has been described will be described. Further, it is assumed that the inverter 21 is in an inoperative state.

  A control unit (not shown) separately provided in the automobile receives a signal based on the closure of the automobile door (S301). The control unit transmits a signal for confirming whether to start the engine based on the signal to the CPU 90.

  And CPU90 transmits the instruction | indication signal for CPU3A, 3B, 3C, 3D to transmit the vehicle interior confirmation signal A to vehicle equipment 1A, 1B, 1C, 1D based on the said signal from a control part.

  Hereinafter, although the operation of the in-vehicle device 1A will be described, the same operation is performed for the in-vehicle devices 1B, 1C, and 1D.

  CPU3A will transmit the vehicle interior confirmation signal A to the transmission part 7A, if the instruction | indication signal mentioned above from CPU90 is received (S302). At this time, the CPU 3A resets the timer 5A. The reset timer 5A starts measuring time. Then, the CPU 3A determines whether or not the in-vehicle confirmation signal B from the portable device 2 demodulated by the receiving unit 8A is transmitted within a predetermined time (S303). The transmitter 7A ASK modulates the in-vehicle confirmation signal A with a carrier wave having a frequency of 125 kHz. Then, the ASK-modulated in-vehicle confirmation signal A from the transmission unit 7A is transmitted via the transmission antenna 9A.

  When the reception antenna 18 of the portable device 2 receives the ASK-modulated in-vehicle confirmation signal A, the demodulator 24 demodulates the ASK-modulated in-vehicle confirmation signal A. If the CPU 11 determines that the vehicle interior confirmation signal A demodulated by the demodulator 24 is transmitted (S401: YES), the CPU 11 transmits the vehicle interior confirmation signal B to the modulator 25 (S402). The modulation unit 25 performs FSK modulation on the vehicle interior confirmation signal B from the CPU 11 with a carrier wave having a frequency of 312 MHz. The vehicle interior confirmation signal B that has been FSK modulated by the modulator 25 is transmitted via the transmission antenna 19.

  When the reception antenna 10A of the vehicle-mounted device 1A receives the FSK-modulated in-vehicle confirmation signal B, the receiving unit 8A demodulates the FSK-modulated in-vehicle confirmation signal B. When determining that the in-vehicle confirmation signal B from the portable device 2 demodulated by the receiving unit 8A has been transmitted (S303: YES), the CPU 3A transmits a confirmation signal to the CPU 90 (S320). Similarly, CPU3B, 3C, 3D of vehicle equipment 1B, 1C, 1D will transmit a confirmation signal to CPU90, if it determines that the vehicle interior confirmation signal B from the portable device 2 was transmitted. The CPUs 3A, 3B, 3C, and 3D do not transmit the vehicle interior confirmation signal B demodulated by the receiving units 8A, 8B, 8C, and 8D within a predetermined time after the vehicle interior confirmation signal A is transmitted. (S303, NO), an unconfirmed signal is transmitted to the CPU 90 (S321).

  CPU90 transmits an engine start permission signal to a control part (not shown) based on the confirmation signal from vehicle equipment 1A, 1B, 1C, 1D (S304). In response to the engine start permission signal from the CPU 90, for example, the control unit starts driving the engine of the automobile. The CPU 90 transmits an engine start non-permission signal to the control unit based on the unconfirmed signals from the in-vehicle devices 1A, 1B, 1C, and 1D (S318). Then, the control unit does not start driving the automobile engine until the key is inserted into the keyhole (S319).

  For example, when the portable person places the portable device 2 somewhere in the vehicle and forgets where the portable device 2 is, the portable person places the portable device 2 in an input unit (not shown) provided in the vehicle. Input instructions for detection. The control unit receives an instruction signal based on an instruction input to the input unit. Then, the control unit transmits a detection signal to the CPU 90 based on the instruction signal. When the CPU 90 receives the detection signal from the control unit (YES in S305), the CPU 3A, 3B, 3C, 3D transmits an instruction signal for transmitting the inverter operation instruction signal to the vehicle-mounted devices 1A, 1B, 1C, 1D. .

  CPU3A will transmit an inverter operation instruction signal to the transmission part 7A, if the instruction | indication signal mentioned above from CPU90 is received (S306). The transmitter 7A ASK-modulates the inverter operation instruction signal with a carrier wave having a frequency of 125 kHz. Then, the ASK-modulated inverter operation instruction signal from the transmission unit 7A is transmitted via the transmission antenna 9A.

  When the receiving antenna 18 of the portable device 2 receives the ASK-modulated inverter operation instruction signal, the demodulator 24 demodulates the ASK-modulated inverter operation instruction signal. When the CPU 11 determines that the inverter operation instruction signal demodulated by the demodulator 24 has been transmitted (YES in S403), the CPU 11 sets the inverter 21 in an operating state (S404).

  When the CPU 3A transmits the inverter operation instruction signal described above, the CPU 3A transmits a distance calculation signal to the transmitter 7A (S307). At this time, the CPU 3A resets the counter 4A, and causes the counter 4A to start counting from the rise of the distance calculation signal. Further, the CPU 3A resets the timer 5A to start timing. Then, the CPU 3A determines whether or not the distance calculation signal is returned from the portable device 2 within a predetermined time (S308). The transmitter 7A ASK modulates the distance calculation signal with a carrier wave having a frequency of 125 kHz. Then, the ASK-modulated distance calculation signal from the transmitter 7A is transmitted via the transmission antenna 9A.

  When the reception antenna 18 of the portable device 2 receives the ASK-modulated distance calculation signal, the demodulation unit 24 demodulates the ASK-modulated distance calculation signal. At this time, the distance calculation signal from the in-vehicle device 1A demodulated by the demodulator 24 is transmitted to the modulator 25 as it is because the inverter 21 is in an operating state (S406). The modulation unit 25 performs FSK modulation on the distance calculation signal from the demodulation unit 24 with a carrier wave having a frequency of 312 MHz. The distance calculation signal that has been FSK modulated by the modulator 25 is transmitted via the transmission antenna 19.

  When the receiving antenna 10A of the vehicle-mounted device 1A receives the FSK-modulated distance calculation signal, the receiving unit 8A demodulates the FSK-modulated distance calculation signal. When determining that the distance calculation signal from the portable device 2 demodulated by the receiving unit 8A has been transmitted (YES in S308), the CPU 3A reads the count value of the counter 4A. Then, the CPU 3A calculates the distance from the in-vehicle device 1A to the portable device 2 based on the count value. Note that the calculation method of the distance from the in-vehicle device 1A to the portable device 2 by the CPU 3A at this time is the same as that in the first embodiment. Then, the CPU 3A transmits the calculated distance information from the in-vehicle device 1A to the portable device 2 to the CPU 90 (S310). Similarly, the CPU 3B of the in-vehicle device 1B transmits distance information from the in-vehicle device 1B to the portable device 2 to the CPU 90 (S311). Further, the CPU 3C of the in-vehicle device 1C transmits distance information from the in-vehicle device 1C to the portable device 2 to the CPU 90 (S312). Further, the CPU 3D of the in-vehicle device 1D transmits distance information from the in-vehicle device 1D to the portable device 2 to the CPU 90 (S313). Further, the CPU 3A calculates the distance from the in-vehicle device 1A to the portable device 2 and transmits an inverter non-operation instruction signal to the transmission unit 7A (S309). The transmitter 7A ASK-modulates the inverter non-operation instruction signal with a carrier wave having a frequency of 125 kHz. Then, the ASK-modulated inverter non-operation instruction signal from the transmission unit 7A is transmitted via the transmission antenna 9A. If the CPU 3A determines that the distance calculation signal demodulated by the receiving unit 8A is not returned within a predetermined time after transmitting the distance calculation signal (NO in S308), the CPU 3A performs distance calculation. Information determined that no signal is returned is stored in order, for example, from address 1 of the Flash memory 6A. At this time, the CPU 3A determines whether or not the information determined that the distance calculation signal is not returned is stored in the address 2 (S316). If the CPU 3A determines that the information is not stored at the address 2 (NO in S316), the CPU 3A transmits the inverter operation instruction signal to the transmitter 7A again (S306). Further, as described above, the CPU 3A resets the timer 5A to start timing, and resets the counter 4A to start counting. If the CPU 3A determines that the distance calculation signal is not returned again (NO in S308), the CPU 3A stores the information determined that the distance calculation signal is not returned, for example, at address 2 of the Flash memory 6A (S316). ). If the CPU 3A determines that the information determined that the distance calculation signal has not been returned is stored in the address 2 (YES in S316), the CPU 3A transmits a signal based on the determination to the CPU 90. CPU90 will discriminate | determine that the portable device 2 is not in a motor vehicle, if the said signal from not only the vehicle equipment 1A but the vehicle equipment 1B, 1C, 1D is received (S317). Then, the CPU 90 transmits an instruction signal to a control unit (not shown) to display on the monitor 92 that the portable device 2 is not in the automobile. Based on the instruction signal from the CPU 90, the control unit causes the monitor 92 to display that the portable device 2 is not in the vehicle (S315).

  As described above, when receiving the above-described distance information from the in-vehicle devices 1A, 1B, 1C, and 1D, the CPU 90 calculates where the portable device 2 is in the vehicle based on the distance information (S314). At this time, the CPU 90 calculates the location where the portable device 2 is located, as described above, with the on-vehicle device 1A as the starting point, the distance point calculated by the CPU 3A from the starting point (FIG. 10, one-dot chain line A), and the on-vehicle device 1B. The starting point is a distance point calculated by the CPU 3B from the starting point (FIG. 10, two-dot chain line B), the in-vehicle device 1C is the starting point, and the distance point calculated by the CPU 3C from the starting point (FIG. 10, broken line C) is It is obtained from the point where the machine 1D is the starting point and the distance point (solid line D in FIG. 10) calculated by the CPU 3D from the starting point coincides. Then, the CPU 90 transmits an instruction signal to the control unit so as to display the calculated location of the portable device 2 on the monitor 92. Based on the instruction signal from the CPU 90, the control unit displays the location where the portable device 2 is on the monitor 92 (S315, FIG. 11).

  As described above, when the portable person forgets where the portable device 2 is located, the CPU 3A, 3B, 3C, 3D determines the distance from each onboard device 1A, 1B, 1C, 1D to the portable device 2 by the distance calculation signal. By calculating, the CPU 90 can calculate the location where the portable device 2 is located.

  According to the above-described embodiment, from the phase difference between the distance calculation signal transmitted from the vehicle-mounted device 1 and the distance calculation signal returned from the portable device 2, the CPU 3 performs the following operations. The distance between the two can be calculated. Further, the distance between the in-vehicle device 1 and the portable device 2 is calculated from the distance calculation signal transmitted from the CPU 3 and the same distance calculation signal transmitted from the CPU 3 as returned from the portable device 2. Since the calculation is performed, it is possible to reliably calculate an accurate distance.

  Further, in communication from the in-vehicle device 1 to the portable device 2, a phase difference can be intentionally generated by performing communication using a low-frequency carrier wave. Further, in the communication from the portable device 2 to the in-vehicle device 1, the phase difference is negligible compared to the phase difference caused by the communication from the in-vehicle device 1 to the portable device 2 by performing communication with a high frequency carrier wave. Can do. That is, the distance from the in-vehicle device 1 to the portable device 2 can be calculated from the phase difference intentionally generated in the communication from the in-vehicle device 1 to the portable device 2.

  Further, when it is determined that the distance between the in-vehicle device 1 and the portable device 2 calculated by the CPU 3 is equal to or greater than a predetermined distance, it is possible to disable communication with the portable device 2. Therefore, for example, even if communication is performed by a relay device interposed between the in-vehicle device 1 and the portable device 2, communication with the portable device 2 can be omitted.

  Further, by setting the inverter 21 to the operating state, it is possible to return a distance calculation signal to the in-vehicle device 1, and the CPU 3 can calculate the distance between the in-vehicle device 1 and the portable device 2. . Furthermore, by making the inverter 21 inoperative, for example, a code read signal transmitted from the vehicle-mounted device 1 is not returned from the portable device 2 as it is.

  Further, since the CPU 3 changes the pattern of the distance calculation signal generated for each predetermined number, for example, it is possible to improve the security for a person who reads the distance calculation signal with a reader or the like. In addition, since the CPU 3 transmits the distance calculation signal until the distance calculation signal from the portable device 2 is returned, the CPU 3 can reliably calculate the distance between the in-vehicle device 1 and the portable device 2. it can.

  In addition, in communication from the vehicle-mounted device 1 that performs communication using a low-frequency carrier wave to the portable device 2, the circuit configuration is facilitated by using ASK modulation suitable for modulation using the low-frequency carrier wave, and interference may occur to some extent. Transmission from the in-vehicle device 1 to the portable device 2 becomes possible. In the communication from the portable device 2 that communicates with the high frequency carrier wave to the in-vehicle device 1, the FSK modulation suitable for the modulation with the high frequency carrier wave is used, so that it is less affected by noise, and the portable device 2 is mounted on the vehicle It is possible to reliably transmit information to the machine 1 without loss.

  Further, by performing communication by spread spectrum in communication from the in-vehicle device 1 to the portable device 2 and communication from the portable device 2 to the in-vehicle device 1, the confidentiality of the signal transmitted by the spread spectrum is increased. In addition, the ability to eliminate interference waves, interference waves, etc. can be significantly increased.

In addition, a timer 5 for detecting a phase difference, a counter 4 that counts with a clock having a predetermined frequency, and information on which the CPU 3 calculates a distance between the in-vehicle device 1 and the portable device 2 based on the count value. It is possible for the CPU 3 to reliably calculate the distance between the in-vehicle device 1 and the portable device 2 using the Flash memory 6 in which is stored. In addition, the timer 5 and the counter 4 are reset every time the CPU 3 transmits a distance calculation signal, so that the CPU 3 erroneously detects the distance between the vehicle-mounted device 1 and the portable device 2 from the two distance calculation signals having the same pattern. It is possible to prevent the distance from being calculated. Therefore, the CPU 3 can calculate the distance between the in-vehicle device 1 and the portable device 2 more reliably.

  Further, the CPU 3 can calculate the distance between the in-vehicle device 1 and the portable device 2 and can unlock the door of the automobile when it is determined that the distance is less than a predetermined distance. It becomes. Further, when it is determined that the distance is equal to or greater than a predetermined distance, the door of the automobile can be locked. That is, it is possible to unlock or lock the door of the automobile without inserting a key (automobile key) into the keyhole.

  Furthermore, when the CPU 3 determines that the distance between the in-vehicle device 1 and the portable device 2 is equal to or greater than a predetermined distance, an alarm unit (not shown) can be operated. Therefore, for example, when the determination unit makes the above-described determination through the relay device, it is possible to notify that communication is being performed through the relay device.

=== Other Embodiments ===
The distance calculation system according to the present invention has been described with respect to the calculation of the distance from the in-vehicle device to the portable device. However, the above description is for facilitating the understanding of the present invention, and the present invention is limited. It is not a thing. The present invention can be changed and improved without departing from the gist thereof.

<< Automobile door unlock >>
In the present embodiment, the driver switches the selector switch (not shown) to unlock the door on the driver's seat or all the doors selected by the carrier. However, the present invention is not limited to this. Absent. For example, in the above-described in-vehicle devices 1A, 1B, 1C, and 1D, when the user enters the area, the CPU 3A calculates the distance between the in-vehicle device 1A and the portable device 2 as described above, and the in-vehicle device 1B The CPU 3B calculates the distance from the portable device 2, the CPU 3C calculates the distance between the in-vehicle device 1C and the portable device 2, and the CPU 3D calculates the distance between the in-vehicle device 1D and the portable device 2. And CPU90 can discriminate | determine whether the portable device 2, ie, a carrier, is approaching the vehicle from the driver's seat side based on the distance information from CPU3A, 3B, 3C, 3D. For example, in FIG. 10, when the distance information calculated by the CPU 3 </ b> B of the in-vehicle device 32 is longer than the distance information calculated by the CPU 3 </ b> A of the in-vehicle device 31, the CPU 90 determines that the wearer is approaching from the passenger seat side. be able to. In this case, for example, when the carrier selects the unlocking of the driver's seat side door with the changeover switch, the CPU 90 instructs the control unit (not shown) to unlock the passenger's seat side door. May be provided.

<< Application of distance calculation system >>
In the present embodiment, the distance calculation system is used in a passive keyless entry system that locks or unlocks a car door without operating a key, but the application target of the present invention is not limited to this.

  A person who needs to specify a whereabouts (for example, a kindergarten or an elderly person; hereinafter referred to as a monitored person) has the portable device 2 and monitors a monitored person having a monitoring device having the same function as the in-vehicle device 1 (hereinafter referred to as a monitored person) Managed by a supervisor). Then, the monitoring device determines whether or not the in-area confirmation signal B is transmitted from the portable device 2 based on the in-area confirmation signal A from the monitoring device, so that the monitored person communicates. It can be determined whether or not it is within a possible range. Then, when the monitoring device determines that the in-area confirmation signal B from the portable device 2 possessed by the monitored person is not transmitted from the portable device 2, for example, the monitoring device sounds an alarm (alarm) to the monitored person. Inform the observer that he / she has left the communicable range. Therefore, it is possible to quickly protect the monitored person by the monitoring person. Further, an identification code may be stored in the flash memory 13 of the portable device 2 of each monitored person, and the identification code may be transmitted from the portable device 2 together with the in-area confirmation signal B. By doing so, it becomes possible for the supervisor to know who is out of the communicable range among the monitored persons. Further, a plurality of monitoring devices are provided as in the second embodiment. Then, the in-area confirmation signal A is transmitted from the plurality of monitoring devices. If the monitored person leaves the communicable range, the monitored person can communicate based on the in-area confirmation signal B received by a plurality of monitoring devices immediately before the monitored person leaves the communicable range. The supervisor can easily know the direction of exiting. This is because the monitoring apparatus determines whether or not the intra-area confirmation signal B is transmitted within a predetermined time t1 after the intra-area confirmation signal A is transmitted. Therefore, the in-area confirmation signal B is transmitted earliest to the monitoring device closest to the monitored person. Therefore, the direction in which the monitored person leaves the communicable range can be determined by the monitoring device closest to the monitored person. Therefore, the search for the monitored person by the monitoring person becomes more reliable. Therefore, it is possible to prevent an accident due to the monitored person leaving the communicable range. Further, when the monitored person leaves the communicable range, the monitoring apparatus determines that the in-area confirmation signal B from the portable device 2 has not been transmitted, and transmits a distance calculation signal. If there is a relay device between the portable device 2 and the monitoring device, the distance calculation signal is returned to the monitoring device via the relay device. The monitoring device calculates the distance between the portable device 2 and the monitoring device from the phase difference between the distance calculation signal when transmitted and the distance calculation signal from the portable device 2. At that time, the monitoring device determines that the distance between the portable device 2 and the monitoring device calculated by the monitoring device is not less than a predetermined distance. Therefore, the monitoring person can easily determine that the monitored person remains out of the communicable range. Therefore, for example, kidnapping or the like of a monitored person by a person possessing a relay device can be prevented.

  Further, for example, the portable device 2 may be used as a home key. In this case, a management device having the same function as the vehicle-mounted device 1 can be provided on the door of the home, and the home door can be used to lock or unlock the key without operating the key as in the first embodiment. Become. If there is a relay device between the portable device 2 and the management device, the management device determines that the distance between the portable device 2 calculated by the management device and the management device is not less than a predetermined distance. Therefore, the management device stops communication with the portable device 2. Therefore, security is improved, and it is possible to prevent damage caused by a thief or the like who attempts to enter a home via a relay device. Similarly, it can be used when entering a building other than the home.

  For example, the portable device 2 may be provided as a valuable item. When the valuables provided with the portable device 2 are lost, a distance calculation signal is transmitted from a searcher having the same function as the in-vehicle device 1. Then, when the searcher approaches the portable device 2 provided for the valuables, the portable device 2 returns a distance calculation signal from the searcher. When the distance calculation signal from the portable device 2 is transmitted to the searcher, the searcher can calculate the distance to the portable device 2. When the distance to the portable device 2 calculated by the searcher becomes a predetermined distance, for example, by sounding an alarm (alarm), the person who owns the searcher confirms that valuables are in the vicinity. It becomes possible to judge.

  Further, for example, a power meter or the like may be provided with the same function as the in-vehicle device 1. In this case, a measurer such as a power meter is allowed to carry the portable device 2. And an electric power meter etc. transmit the signal for distance calculation, in order to discriminate | determine whether the portable device 2 is less than the predetermined distance. And when a power meter etc. discriminate | determine that the portable device 2 is less than a predetermined distance, you may provide so that the data value which a power meter etc. measures may be transmitted to the measuring device which a measurer has. By doing so, it is possible to collect the data values without contact with the power meter or the like in collecting the data values measured by the power meter or the like. Furthermore, in recent years, data values measured by a power meter or the like can be collected via the Internet or the like, but the data values may be read by a third party. However, if the data value measured by the power meter or the like is collected using the power meter or the portable device 2 as described above, the risk of reading the data value by a third party is reduced and security can be improved. It becomes. Also, if there is a relay device between the portable device 2 and the power meter or the like, the power meter or the like unless the distance between the portable device 2 and the power meter or the like calculated in the power meter or the like is less than a predetermined distance Determine. Therefore, the power meter or the like stops communication with the portable device 2. Therefore, it is possible to prevent the data value measured by the power meter from being read via the relay device.

  Further, a person who needs protection by a guardian, for example, a child, carries the portable device 2, and a searcher having the same function as the in-vehicle device 1 is provided on the utility pole. And when the child who possesses the said portable device 2 is in kidnapping etc., it can also serve as information for tracking a child. In this case, the searcher provided on the utility pole transmits a distance calculation signal. When the child carrying the portable device 2 passes near the utility pole provided with the search device, a distance calculation signal from the portable device 2 is transmitted to the search device. At this time, the searcher calculates the distance to the portable device 2 and stores the time information when the distance calculation signal is transmitted from the portable device 2 in, for example, the Flash memory 6. Then, for example, by reading the time information stored in the flash memory 6 of the search machine by the police or the like, it becomes possible to determine when and how far the child has passed from the search machine. It is also possible to grasp the place where the child is present by distributing the above-mentioned time information by the searcher to the guardian of the child through the communication network. Furthermore, if there is a relay device between the portable device 2 and the search device, for example, an alarm unit (not shown) of the portable device 2 can be alerted. Therefore, it is possible to quickly know that a child may be kidnapped, for example, by someone whose guardian or the like has a repeater. Therefore, parents or the like can prevent children from being kidnapped.

It is a functional block diagram which shows an example of the whole structure of the distance calculation system which concerns on this invention. It is a flowchart which shows an example of operation | movement of the distance calculation system which concerns on this invention. It is a flowchart which shows an example of operation | movement of the distance calculation system which concerns on this invention. It is a timing chart which shows an example of operation | movement of the distance calculation system which concerns on this invention. It is a figure which shows the change of the signal for distance calculation. It is a timing chart which shows an example of operation | movement of the distance calculation system which concerns on this invention. It is a figure which shows the change of the signal for distance calculation. It is a figure which shows an example of the whole structure of the distance calculation system which concerns on this invention. It is a flowchart which shows an example of operation | movement of the distance calculation system which concerns on this invention. It is a figure which shows the detection of the portable device 2 by vehicle equipment 1A, 1B, 1C, 1D. It is a figure which shows an example of the display screen of the monitor. It is a figure which shows communication of the vehicle equipment 101 and the portable device 102 via the relay machines A and B. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 In-vehicle machine 2,102 Portable machine 3, 11, 90 CPU
4 Counter 5, 27 Timer 6, 13 Flash memory 7 Transmitting unit 8 Receiving unit 9, 19 Transmitting antenna 10, 18 Receiving antenna 12 Input unit 14 DET
15 Modulator 16, 17 RF
20, 21, 22 Inverter 23 Flag 24 Demodulator 25 Modulator 26 OSC
92 Monitor

Claims (11)

A distance calculation system for calculating a distance between a first communication device and a second communication device,
The first communication device is
A transmitter for transmitting a distance calculation signal for calculating a distance to the second communication device;
By detecting the distance calculation signal returned from the second communication device, a detection unit that detects a phase difference between the distance calculation signal when transmitted and the distance calculation signal when received When,
A calculation unit that calculates a distance to the second communication device based on the phase difference detected by the detection unit;
The second communication device is
A reply unit for returning the distance calculation signal transmitted from the first communication device;
A distance calculation system characterized by that. The first communication device is
A first modulation unit that modulates the distance calculation signal with a carrier of a first frequency; and the distance calculation modulated by a carrier of a second frequency higher than the first frequency from the second communication device. A first demodulator that demodulates the signal,
The second communication device is
A second demodulation unit that demodulates the distance calculation signal modulated by the first modulation unit from the first communication device; and a second demodulation unit that demodulates the distance calculation signal demodulated by the second demodulation unit. A second modulation unit that modulates with a carrier wave having a frequency of
The distance calculation system according to claim 1. The first communication device is
A determination unit that determines whether a distance between the first communication device and the second communication device calculated by the calculation unit is less than a predetermined distance;
Based on the determination result when the determination unit determines that the distance between the first communication device and the second communication device calculated by the calculation unit is equal to or greater than the predetermined distance, Stopping communication with the second communication device;
The distance calculation system according to claim 1 or 2, characterized by the above. The second communication device is
A switching unit that puts the reply unit into an operating state to send back the distance calculation signal;
The first communication device is
Transmitting a switching signal for setting the return unit in an operating state so that the calculation unit calculates a distance to the second communication device;
The switching unit sets the reply unit to an operating state based on the switching signal from the first communication device.
The distance calculation system according to any one of claims 1 to 3, wherein: The first communication device is
A generator for generating the distance calculation signal;
The transmitter is
Until the first communication device receives the distance calculation signal sent back from the second communication device, repeatedly transmits the distance calculation signal generated by the generation unit,
The generator is
Each time a predetermined number of the distance calculation signals are generated, the pattern of the distance calculation signal is changed.
The distance calculation system according to any one of claims 1 to 4, wherein: The first modulation unit performs ASK modulation on the distance calculation signal with a carrier wave of the first frequency,
The second demodulator demodulates the distance calculation signal ASK-modulated by the first modulator from the first communication device,
The second modulation unit FSK-modulates the distance calculation signal demodulated by the second demodulation unit with a carrier wave of the second frequency,
The first demodulator demodulates the distance calculation signal FSK-modulated by the second modulator from the second communication device.
The distance calculation system according to any one of claims 2 to 5, wherein To perform communication between the first communication device and the second communication device using spread spectrum,
The first modulation unit first-modulates the distance calculation signal with a carrier wave having the first frequency, and then second-orders (spreads) the distance calculation signal first-order modulated with the carrier wave having the first frequency. ) Modulate and
The second demodulator despreads and demodulates the distance calculation signal that is second-order (spread) modulated by the first modulator from the first communication device,
The second modulation unit first modulates the distance calculation signal despread and demodulated by the second demodulation unit with the carrier wave of the second frequency, and then 1 with the carrier wave of the second frequency. Second-order (spreading) modulation of the distance-modulated signal for distance calculation,
The first demodulator despreads and demodulates the distance calculation signal that is second-order (spread) modulated by the second modulator from the second communication device.
The distance calculation system according to any one of claims 2 to 5, wherein The first communication device is
A timer that counts the time until the first communication device receives the distance calculation signal that is reset each time the transmission unit transmits the distance calculation signal and is returned from the second communication device;
A counter that is reset every time the timer is reset, and that counts the phase difference detected by the detection unit with a clock having a predetermined frequency;
A storage unit storing information on which the calculation unit calculates a distance between the first communication device and the second communication device based on a count value of the counter;
The detector is
Detecting the time counted by the timer as the phase difference between the distance calculation signal when transmitted and the distance calculation signal when received;
The calculation unit includes:
A distance between the first communication device and the second communication device based on a count value obtained when the counter counts the phase difference with the clock having the predetermined frequency and information stored in the storage unit. To calculate,
The distance calculation system according to claim 1, wherein: The first communication device is provided in an automobile;
For the control unit that controls the unlocking or locking of the door of the automobile,
The determination result when the determination unit determines that the distance between the first communication device and the second communication device calculated by the calculation unit is less than the predetermined distance is displayed on the door. As a signal to unlock,
When the determination unit determines that the distance between the first communication device and the second communication device calculated by the calculation unit is equal to or greater than the predetermined distance, Supply as a signal to lock,
The distance calculation system according to any one of claims 3 to 8, wherein The second communication device has an alarm unit for issuing an alarm,
The first communication device is
Based on the determination result when the determination unit determines that the distance between the first communication device and the second communication device calculated by the calculation unit is equal to or greater than the predetermined distance, The alarm unit transmits an alarm signal for issuing an alarm,
The alarm unit is
Issuing an alarm based on the alarm signal from the first communication device;
The distance calculation system according to claim 3, wherein the distance calculation system includes: A distance calculation method of a distance calculation system for calculating a distance between a first communication device and a second communication device,
The first communication device transmits a distance calculation signal for calculating a distance to the second communication device,
The second communication device returns the distance calculation signal transmitted from the first communication device,
The first communication device receives the distance calculation signal returned from the second communication device, so that the phase difference between the distance calculation signal when transmitted and the distance calculation signal when received is received. And calculating a distance to the second communication device based on the phase difference.
The distance calculation method of the distance calculation system characterized by the above-mentioned.

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