JP3123361B2 - Mobile communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a communication device which constitutes a ground station for each communication area obtained by dividing a region through which a mobile object passes into a plurality of communication areas. By transmitting and activating the transponder mounted on the moving body that has entered each communication area, predetermined data communication can be performed between the communication device on the ground station side and the transponder entering the communication area of the communication device. The present invention relates to a mobile communication system that starts the communication.

[0002]

2. Description of the Related Art Hitherto, as one of mobile communication systems, a pilot for starting has been provided from a ground station installed on the ground in order to reduce power consumption on a transponder mounted on a mobile. When a signal is transmitted and the responder receives a pilot signal of a predetermined level or more, it determines that the mobile unit has entered a communication area where communication with the ground station is possible, and activates an internal communication circuit. Such is known.

In this type of mobile communication system,
When the answering machine activates the communication circuit, communication with the answering machine cannot be started unless the ground station detects that fact. Conventionally, for example, as shown in FIG. 7 (a), on the ground station side, together with the pilot signal, a response signal indicating the fact (for example, information indicating the type of the transponder) from the transponder which activated the communication circuit. Is transmitted, and the transponder that has activated the communication circuit receives the interrogation signal and returns a response signal (data 2) corresponding to the interrogation signal. . When the ground station receives the response signal, it identifies the transponder that has entered the communication area from the response signal, and performs predetermined data communication with the transponder (data 3, 4 shown in FIG. 7). , 5,6
... exchange).

[0004] On the other hand, in such a mobile communication system, there is no problem if the ground station and the transponder can communicate only in one-to-one correspondence. If there are a large number of gates that pass through and ground stations are provided at each gate to charge each car that passes through each gate, the communication area of each ground station overlaps. Interference may occur between the vehicle and a transponder mounted on a car passing through each gate, and communication may not be possible.

Therefore, conventionally, in a mobile communication system in which a plurality of ground stations are arranged adjacent to each other,
It has been considered that the transmission period of a signal from each ground station is time-divided. In other words, the transmission period of the signal from the ground station is time-divided, so that the transponder that receives the pilot signal and starts the communication circuit receives only the interrogation signal from the ground station that transmitted the pilot signal. , A response signal can be transmitted.

[0006]

However, in such a countermeasure, it is only necessary to be able to receive the interrogation signal from the ground station that transmitted the pilot signal after activating the communication circuit on the transponder side. If the reception fails, there is a problem that the transponder cannot execute communication with the ground station that transmitted the pilot signal.

For example, as shown in FIG. 7B, when two adjacent ground stations A and B transmit pilot signals A and B and data A1 and B1 as interrogation signals in a time division manner, The aircraft enters the communication area of ground station A,
After starting the communication circuit by the pilot signal A, if the reception of the interrogation signal (data A1) from the ground station A fails,
Since the ground station A is in a standby state for an interrogation signal,
An interrogation signal (data B1) transmitted from the ground station B is received, and a response signal (data A2) is transmitted.

[0008] In this case, if the radio wave transmitted from the transponder is strong, the response signal (data A2) is received by the ground station B having a different communication area.
If the erroneous communication is performed and the transmission radio wave from the transponder is weak, the response signal (data A2) from the transponder is not received by any ground station, as shown in FIG. The transponder repeatedly executes the reception of the interrogation signal (data B1) and the transmission of the response signal (data A2).

[0009] Such a problem generally occurs because the communicable area between the ground station and the transponder is closer to the communicable area (downlink area) from the ground station to the transponder side. However, because it is considerably larger than the communication area (uplink area) from the transponder to the ground station,
Normally, even if the transponder receives the interrogation signal (data B1) from the ground station B having a different communication area and transmits the response signal (data A2) as described above, the response signal (data A
2) is not received by the ground station B, and FIG.
As shown in (1), the transponder repeats reception of the interrogation signal (data B1) and transmission of the response signal (data A2).

The present invention has been made in view of such a problem, and in a mobile communication system in which a plurality of ground stations are provided adjacent to each other as described above, the mobile body is located in a communication area of any of the ground stations. It is an object of the present invention to ensure that a transponder mounted on the mobile body can communicate with a ground station in the communication area when the vehicle enters.

[0011]

Means for Solving the Problems According to the first aspect of the present invention which has been made to achieve the above object, the present invention is provided in a communication area obtained by dividing a region through which a moving object passes into a plurality of areas, and is mounted on the moving object. When transmitting a link signal in which a pilot signal for activating the mobile communication means and an interrogation signal for transmitting a response signal from the mobile communication means are sequentially transmitted, and receiving the response signal after transmitting the link signal, A plurality of fixed communication means for performing data communication with the mobile communication means which has transmitted the response signal, and transmission timing control means for executing the transmission of the link signal and data from each of the fixed communication means in a time-division manner; A ground station with
The mobile communication means is provided in the mobile body, receives a query signal and data transmitted from the fixed communication means, and transmits a response signal or data corresponding to the received signal, and the mobile communication means transmits the response signal or data corresponding to the received signal. Incoming pilot signal, and when the pilot signal is above a predetermined level,
Determining means for determining that the moving object has entered the communication area; and activation means for activating the mobile communication means when the determining means determines that the moving object has entered the communication area. In a mobile communication system configured by a transponder provided with:
At the time of the data communication, a communication signal with the pilot signal added before the data to be transmitted is transmitted, and the responding unit receives the pilot signal by the determination unit and the mobile unit performs the communication. When it is determined that the mobile station has entered the area, the fixed communication means permits the receiving operation of the mobile communication means for a predetermined time during which the interrogation signal or the data is transmitted. The present invention is characterized in that a prohibiting reception time limiting means is provided.

According to a second aspect of the present invention, in the mobile communication system according to the first aspect, each of the fixed communication means constituting a ground station is activated a predetermined number of times at predetermined time intervals as the pilot signal. The transmitting means for transmitting a carrier wave, the determination means constituting the transponder, the signal processing means for detecting and amplifying the starting carrier wave, and compares the output signal from the signal processing means with a level determination reference value. Level determining means for generating a pulse signal having a pulse width corresponding to the level of the starting carrier wave, and converting the pulse signal generated by the level determining means into a starting pulse signal having a constant pulse width. Determining pulse generating means, integrating means for integrating a pulse signal output from the determining pulse generating means, and moving when an integrated value of the integrating means becomes equal to or more than a reference value for starting determination. There has been comprising the, and initiation determining means that it has entered the communication area.

[0013]

In the mobile communication system according to claim 1, the fixed communication means is provided on the ground station side for each communication area obtained by dividing the area through which the mobile passes into a plurality of areas. The transmission timing control means causes transmission from these fixed communication means to be executed in a time-division manner.

[0014] Each fixed communication means usually operates at each transmission timing time-divided by the transmission timing control means.
A link signal is transmitted in which a pilot signal for activating the mobile communication means mounted on the mobile body and an interrogation signal for causing the mobile communication means to transmit a response signal are sequentially continuous.

Further, each of the fixed communication means receives a response signal transmitted from the mobile communication means after transmitting the link signal, and thereafter, at each transmission timing set by the transmission timing control means, sets a pilot signal. By transmitting the data to which the signal is added, data communication is performed with the mobile communication unit that has transmitted the response signal.

On the other hand, on the transponder side provided in the mobile body,
First, the determination means receives a pilot signal transmitted from the fixed communication means constituting the ground station, and when the pilot signal is at a predetermined level or higher, the mobile station determines whether any of the fixed communication means constitutes the ground station. It is determined that the vehicle has entered the communication area of the means. When the determining means determines that the moving object has entered the communication area, the mobile communication means is activated.

The mobile communication means receives the interrogation signal and the data transmitted from the fixed communication means after activation, and transmits a response signal or data corresponding to the received signal. After the receiving time limiting means, after the determining means receives the pilot signal and determines that the mobile has entered the communication area, the fixed communication means which has transmitted the pilot signal transmits only the interrogation signal or data for a predetermined time. Is limited to

In other words, according to the present invention, each fixed communication means constituting the ground station always transmits a signal to which a pilot signal is added when transmitting an interrogation signal or data for data communication. On the side, the determination means receives the pilot signal attached to the transmission signal and not only activates the mobile communication means when it is determined that communication with the ground station is enabled, but also thereafter, only for a predetermined time. Permit the receiving operation of the mobile communication means to receive a response signal, and further,
After the activation of the mobile communication means and the permission of the reception operation for receiving the response signal, each time the determination means receives the pilot signal and determines that the communication with the ground station is enabled, the mobile communication means is activated for a predetermined time. The mobile communication means receives only the transmission signal from the fixed communication means provided in the communication area where the moving object has entered by permitting the reception operation of the mobile communication means.

Therefore, according to the present invention, the mobile communication means is used to receive a transmission signal (that is, an interrogation signal or data) transmitted from the fixed communication means to perform data communication following the pilot signal. Even if the transmission fails and a response signal or data corresponding to the signal cannot be transmitted, it is possible to reliably receive the transmission signal transmitted at the next transmission timing from the fixed communication unit that should execute data communication. become able to.

Therefore, according to the present invention, even if the mobile communication means fails to receive a response signal or the like attached to the pilot signal, the mobile communication means differs from the communication area where the moving body has entered, as in the conventional device. There is no such thing as performing erroneous data communication with the fixed communication means, or repeatedly receiving the inquiry signal and response signal transmitted from the other fixed communication means. In addition, accurate data communication can be performed with the fixed communication means in the communication area where the moving object has entered.

Next, in the mobile communication system according to the second aspect, each fixed communication means constituting the ground station transmits a starting carrier wave a predetermined number of times at predetermined time intervals as a pilot signal. On the other hand, in the determination means on the transponder side,
First, the signal processing means detects and amplifies the starting carrier transmitted from the ground station side as a pilot signal, and the level determination means determines the magnitude of the output signal from the signal processing means and the reference value for level determination. By comparison, a pulse signal having a pulse width corresponding to the level of the starting carrier is generated. Then, the determination pulse generating means converts the generated pulse signal into a pulse signal for activation determination having a fixed pulse width,
The integrator integrates the signal converted to the constant pulse width. judge.

This is because if the reception level of the pilot signal is simply determined to determine that the moving object has entered the communication area, the communication may be performed when noise or the like is superimposed on the reception signal of the pilot signal. This is because an entry into the area may be erroneously determined.

That is, the noise does not change periodically, and no matter how high the level is, the pulse signal is not periodically generated by the level determining means. Therefore, in the present invention, a predetermined starting carrier is transmitted as a pilot signal a plurality of times at predetermined time intervals from each fixed communication device constituting a ground station, and the transponder side detects and amplifies the starting carrier. The level of the output signal from the means is determined by the level determining means, the resulting pulse signal is converted into a pulse signal having a constant pulse width, and the pulse signal is integrated. Only when the signal is repeatedly generated for a predetermined number or more at a predetermined time interval (in other words, only when a pilot signal of a predetermined level or more transmitted from the fixed communication means is received), the signal is determined to be equal to or more than the reference value for activation determination. By generating an integrated value, and comparing the integrated value with a reference value for starting determination, it is determined whether or not the moving object has entered the communication area. Is are you.

Therefore, according to the present invention, in the transponder, the determining means accurately determines that the moving object has entered the communication area of any of the fixed communication means constituting the ground station, and performs the mobile communication. The activation of the means and the receiving operation of the mobile communication means can be minimized. Therefore, according to the present invention, it is possible to further reduce the power consumption of the mobile communication means as compared with the case where the entry into the communication area is determined only by comparing the signal level obtained by detecting and amplifying the pilot signal with the reference level. Becomes possible.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, a case where the present invention is applied to a toll road charging system for charging a toll for a car traveling on a toll road will be described below. In the following description, FIG. 1 shows a configuration of a transponder mounted on an automobile, and FIG. 2 shows a configuration of a ground station forming a toll road charging system.

As shown in FIG. 2, the ground station according to the present embodiment includes a plurality of lanes L1, L2, formed at the entrance and exit of a toll road.
, Ln, and each of the lanes L1, L2,.
n is a communication area, and the corresponding lanes L1, L2,.
A plurality of antennas 2-1 and 2- for performing predetermined data communication with a transponder mounted on a car passing through Ln.
, 2-n and a plurality of data transmission / reception as fixed communication means for performing data communication between the transponders via the antennas 2-1, 2-2, ..., 2-n. 4-1, 4-2, ...,
4-n and each of these data transmission / reception units 4-1, 4-2,.
-n, a communication control unit 6 for sequentially transmitting a pilot signal and data for starting the answering machine at predetermined time intervals. A billing device (host computer) 8 for issuing a bill or the like based on the data is connected.

Here, the communication control unit 6 corresponds to transmission timing control means, and the data transmission / reception units 4-1 and 4--
, 4-n perform data transmission operations in a time-division manner at predetermined time intervals, and the data transmission / reception units 4-1, 4-2,. When the data is received from the device, the received data is read, and the transmission data from the data transmission / reception units 4-1 4-2,..., 4-n that received the data is controlled in accordance with the received data. ., 4-n and the corresponding transponders passing through the corresponding lanes L1, L2,..., Ln. For
It is composed of a one-chip microcomputer including a CPU, a ROM, a RAM, and the like.

Each of the data transmission / reception units 4-1 and 4-2,
,..., 4-n have not started data communication with the transponder, first, a certain time (1 msec in this embodiment) .), 10 kHz (1 cycle: 0.1 ms)
c)), the data transmitting / receiving unit 4 transmits a pilot signal corresponding to the pulse signal from the data transmitting / receiving unit 4 via the antenna 2, and then responds from the transponder that has received the pilot signal. A question signal for transmitting a signal is transmitted. As a result, from each of the antennas 2-1, 2-2,..., 2-n on the ground station side, a transmission signal is radiated as a pilot signal sequentially at a predetermined interval of 0.05 msec. At the same time, an interrogation signal is transmitted following the pilot signal.

By transmitting the signal (link signal) composed of the "pilot signal + interrogation signal", a response signal corresponding to the interrogation signal is transmitted from the transponder side, and the data transmission / reception units 4-1 and 4-- When a response signal is received at 2,..., 4-n, the response signal is read, and data corresponding to the response signal is transmitted from the data transmission / reception unit 4 that has received the response signal. Data communication is started between the transmission / reception unit 4 and the transponder which has transmitted the response signal. At the time of this data communication, the data transmission / reception units 4-1, 4-2,... The transmission of data from is performed at regular intervals, similarly to the transmission of the ring signal, and
After transmitting the pilot signal in the same manner as above, data for data communication is transmitted.

The data transmission / reception units 4-1 and 4-
Interrogation signals and data to be transmitted subsequent to the pilot signal from 2,..., 4-n are generated as serial data synchronized with a transmission clock of 100 kHz.
The generated serial data is transmitted to each data transmitting / receiving unit 4-
Output to 1, 4-2,..., 4-n allows antenna 2-
Signals that change faster than pilot signals are emitted as data signals from 1, 2-2,..., 2-n.

On the other hand, a transponder mounted on an automobile is shown in FIG.
As shown in FIG. 1, a communication antenna 10 and a power supply unit 12 for generating a constant power supply voltage VCC using a vehicle-mounted battery as a power supply.
And a receiving circuit 16 for operating by receiving power supply from the power supply unit 12 via the power switch 14 and performing data communication with the ground station via the antenna 10.
a and a data transmission / reception unit 16 as a mobile communication means including a transmission circuit 16b, and operates by receiving power supply from the power supply unit 12 via the power switch 14.
A communication control unit 18 for controlling the data transmission / reception unit 16 to transmit and receive predetermined data; and a communication control unit 18 which always operates by directly receiving power supply from the power supply unit 12 to reduce a signal level of a pilot signal received by the antenna 10. Based on the information, it is determined whether the vehicle (that is, the answering machine) has entered a communication area where data communication with any of the data transmission / reception units 4-1, 4-2,... If it is determined that the vehicle has entered the communication area, the activation signal VWU1 is output, the power switch 14 is turned on, and the reception signal from the reception circuit 16a in the data transmission / reception unit 16 is fixed through the AND gate AND. And a start-up determination unit 20 for outputting the communication control unit 18 for only the time.

The AND gate AND receives, at one input terminal, an interrogation signal or data from the ground station demodulated by the receiving circuit 16a, and at the other input terminal, an activation discriminator 20.
When the reception permission signal VWU2 is at a high level, the output data from the reception circuit 16a is output to the communication control unit 18.

The communication control unit 18 includes a CPU, a ROM, a RAM and the like, like the communication control unit 6 on the ground station side.
It is composed of a chip microcomputer,
Receiving circuit 16a input via AND gate AND
By outputting response data corresponding to the output data (a query signal or data transmitted from the ground station side) to the data transmission / reception unit 16, the response data is transmitted via the transmission circuit 16 b and the antenna 10. Data to the ground station.

Next, as described above, the start determination unit 20 that outputs the start signal VWU1 and the reception permission signal VWU2 includes the determination unit, the start unit, and the reception time limit unit of the present invention, and is shown in FIG. It is configured as follows. As shown in FIG. 3, the activation determination unit 20 includes a detection unit 22 that detects a signal received from the antenna 10, an amplification unit 24 that amplifies the reception signal detected by the detection unit 22, and an amplification unit 24 that amplifies the reception signal. The received signal is compared with a reference voltage VTH1 for level determination.
A level determination unit 26 that outputs a level signal, and a determination pulse generation unit 28 that generates a high-level signal (that is, a pulse signal having a constant pulse width) for a fixed time after the rise of the pulse signal output from the level determination unit 26 And an integration unit 30 for integrating a pulse signal having a constant pulse width output from the determination pulse generation unit 28, and comparing the integrated value of the pulse signal by the integration unit 30 with a reference voltage VTH2 for start-up determination. When the value exceeds the reference voltage VTH2,
It is determined that the transponder has entered a communication area where communication with the ground station is possible, and Hi
GH level drive signal, and outputs a start signal VWU1 for turning on the power switch 14 in response to the drive signal from the start determiner 32, and also after the fall of the drive signal. A first output unit 34 as a starting means for continuously outputting the starting signal VWU1 for a predetermined period.
Similarly, receiving the drive signal from the activation determination unit 32, the reception permission signal VWU2 is output, and the reception permission signal VWU2 is continuously output for a predetermined time shorter than the activation signal VWU1 even after the fall of the drive signal. And a second output unit 36 as time limiting means.

Here, the amplifying section 24 is constituted by cascading three stages of inverting amplifying circuits including the operational amplifier OP1 shown in FIG. Each inverting amplifier circuit includes a capacitor C1 and a resistor R1 for inputting a reception signal to an inverting input terminal of the operational amplifier OP1, and a voltage dividing resistor for applying a predetermined voltage obtained by dividing the power supply voltage VCC to a non-inverting input terminal of the operational amplifier OP1. Devices R4a and R4b, an output resistor R3 connected to the output terminal of the operational amplifier OP1,
3 and a feedback resistor R2 and a capacitor C2 respectively connecting the output terminal of the operational amplifier OP1 and the inverting input terminal of the operational amplifier OP1.
It is configured as an amplifier circuit that inverts and amplifies a high-frequency signal in a predetermined frequency band (around 10 kHz in this embodiment) corresponding to a pilot signal and outputs the inverted signal.

Next, the level determination section 26 for determining the level of the received signal amplified by the three-stage inverting amplifier circuit in the amplifier section 24 includes an operational amplifier OP2 and this operational amplifier O2.
A comparator constituted by voltage dividing resistors R5 and R6 for applying a reference voltage VTH1 obtained by dividing the power supply voltage VCC to the inverting input terminal of P2, and comprising an operational amplifier OP2
Receiving the received signal output from the amplifier 24 at the non-inverting input terminal of the amplifier, the pulse signal which becomes High level when the received signal is higher than the reference voltage VTH1 and becomes Low level when the received signal is lower than the reference voltage VTH1. Output.

Next, the determination pulse generator 28 includes an operational amplifier OP3, input resistors R7 and R9 for inputting output pulses from the level determiner 26 to the non-inverting and inverting input terminals of the operational amplifier OP3, respectively, and the operational amplifier OP3. A grounding resistor R8 for grounding the non-inverting input terminal of OP3, a resistor R10 for applying the power supply voltage VCC to the inverting input terminal of the operational amplifier OP3, and one end connected to the inverting input terminal of the operational amplifier OP3 and the other end grounded. And a capacitor C3.

Here, in the determination pulse generating section 28,
When the output from the level determination unit 26 is stable,
The input terminals of the operational amplifier OP3 are at the same level, and no signal is output from the operational amplifier OP3. However, when the output from the level determination unit 26 changes from Low to High (that is, at the time of rising of the pulse signal), the level of the inverting input terminal of the operational amplifier OP3 grounded via the capacitor C3 is required for charging the capacitor C3. Since the level temporarily drops with respect to the level of the non-inverting input terminal by the time, the output of the operational amplifier OP3 becomes the High level for a certain time due to the level difference. On the other hand, when the output from the level determination unit 26 changes from High to Low level (that is, at the time of the falling edge of the pulse signal), the level of the inverting input terminal of the operational amplifier OP3 grounded via the capacitor C3 changes to the level of the non-inverting input terminal. Although the output level temporarily rises with respect to the level, the output from the operational amplifier OP3 is Low.
The level remains unchanged and no signal is output from the operational amplifier OP3.

Accordingly, a high-level signal (pulse signal) is output from the determination pulse generator 28 for a certain period of time after the output pulse from the level determiner 26 rises. The output time of the pulse signal (that is, the pulse width) is determined by a time constant determined by the resistance value of the resistor R9 and the capacitance of the capacitor C3, and is always constant.

Next, the integrator 30 receiving the pulse signal from the determination pulse generator 28 includes a resistor R11 whose one end is connected to the output terminal of the determination pulse generator 28, and a second end of the resistor R11. An anode is connected to the diode D1 for preventing a current from flowing back to the determination pulse generating unit 28, a ground resistor R12 connected to the cathode of the diode D1, and a diode D1 connected in parallel to the ground resistor R12. And a charging capacitor C4.

In the integration section 30, when a high-level signal (pulse signal) is output from the determination pulse generation section 28, the capacitor C4 is charged by this signal via the resistor R11. When the output from the generator 28 goes to a low level, the electric charge charged in the capacitor C4 is discharged via the resistor R12. In this embodiment, the resistance of the resistor R12 is equal to the resistance of the resistor R11. On the other hand, several tens of times (for example, the resistor R11 is 30 kΩ
On the other hand, since the resistor R12 is set to 1 MΩ), when the pulse signal rises, the capacitor C4 is quickly charged, and when the pulse signal falls,
After that, it is gradually discharged. Therefore, when a repetitive pulse signal is input from the determination pulse generation unit 28, the terminal voltage of the capacitor C4 increases every time the pulse signal is input.

Next, the start-up judging section 32 sets the operational amplifier OP
4 and a voltage-dividing resistor R13, R14 for applying a reference voltage VTH2 obtained by dividing the power supply voltage VCC to an inverting input terminal of the operational amplifier OP4, and configured as a comparator. Receiving the output voltage from the integrator 30 (that is, the terminal voltage of the capacitor C4), and determines the magnitude of this voltage (in other words, the integral value) and the reference voltage VTH2. Therefore, the start determination unit 3
2, the output voltage from the integrator 30 is equal to the reference voltage VTH2.
When this is the case, a High level signal is output.

Next, the first output section 34 which receives the output signal from the start-up judging section 32 as described above is provided with a diode D2 for preventing a current from flowing back whose anode is connected to the output terminal of the start-up judging section 32, It comprises a capacitor C5 having a relatively large capacity provided between the cathode of the diode D2 and the ground line, and outputs the terminal voltage of the capacitor C5 as a start signal VWU1 for driving the power switch 14.

That is, when the output signal from the operational amplifier OP4 of the activation judging unit 32 becomes High level, the first output unit 34 outputs this signal as an activation signal VWU1 for turning on the power switch 14. Not only that, this signal charges the large capacitor C5,
Even after the output of the operational amplifier OP4 becomes low level, the start signal VWU1 is continuously output at least for a time longer than the signal transmission time interval from one data transmission / reception unit 4 on the ground station side.

On the other hand, similarly to the first control unit 34, the second output unit 36 receiving the output signal from the start-up determination unit 32 is a diode for preventing a reverse current of the current whose anode is connected to the output terminal of the start-up determination unit 32. D3 and a relatively small capacitor C6 provided between the cathode of the diode D3 and the ground line.
6 is output as a reception permission signal VWU2.

That is, when the output signal from the operational amplifier OP4 of the activation judging unit 32 becomes High level, the second output unit 36 not only outputs this signal to the AND gate AND as the reception permission signal VWU2, but also This signal charges the capacitor C6, which has a smaller capacity than the capacitor C5. Even after the output of the operational amplifier OP4 becomes Low level, only during the transmission time of the interrogation signal or data transmitted from the ground station following the pilot signal. , Reception permission signal VWU
It keeps outputting 2.

In the start determination unit 20 of the present embodiment configured as described above, first, the vehicle approaches the entrance / exit of the toll road, and a plurality of data transmission / reception units 4-1 and 4-2 are provided. ,
.., 4-n enters a communication area where communication with any of the data transmitting / receiving units 4 is possible, and is periodically transmitted from the data transmitting / receiving unit 4 by the antenna 10 in a time-division manner. When the pilot signal is received, the detection unit 22 detects the received signal, and the amplification unit 24 inverts and amplifies the detected reception signal in three stages. Therefore, as shown in FIG.
The amplifying unit 24 repeats (in this embodiment, 10 times in 1 msec.) According to the output of the pilot signal from the ground station.
A changing signal will be output.

Then, the level judging section 26 outputs a pulse signal which goes high when this signal becomes higher than the reference voltage VTH1, and the judging pulse generating section 28 outputs a pulse signal after the rising of this pulse signal. Since a pulse signal having a constant pulse width which becomes High level for a fixed time is output, the terminal voltage of the capacitor C4 of the integrator 30 increases stepwise according to the number of input pulse signals.

On the other hand, in this embodiment, the reference voltage VTH2 of the start-up judging section 32 is set to the output voltage of the integrating section 30 when a predetermined number (five in the figure) of pilot signals of pulse signals are inputted to the integrating section 30. Is set to roughly correspond to
As shown in FIG. 4, the determination pulse generation unit 28 to the integration unit 30
At the time when five consecutive pulse signals having a constant pulse width are input in synchronization with the transmission cycle of the pilot signal from the ground station, the activation determination unit 32 determines that fact, and the activation determination unit 32 Becomes high level.

As a result, in this embodiment, the reference voltage VTH1
When five or more of the above pilot signals are continuously input, the first output unit 34 and the second output unit 36 respectively
The activation signal VWU1 and the reception permission signal VWU2 are output,
The power switch 14 is turned on, the data transmission / reception unit 16 and the communication control unit 18 are activated, and the reception data from the reception circuit 16a is output to the communication control unit 18 via the AND gate AND. Become.

Next, the pilot signal is transmitted periodically from each of the data transmitting / receiving sections 4-1, 4-2,..., 4-n in a time-division manner. At this point, since transmission is not performed until the next transmission timing, the electric charge accumulated in the capacitor C4 of the integration unit 30 is discharged via the resistor R12, and the output from the integration unit 30 is thereafter output. The voltage falls below the reference voltage VTH2, and the output signal from the start determination unit 32 is inverted from the high level to the low level.

However, the first output section 34 and the second output section 3
6 are provided with capacitors C5 and C6, respectively, so that when the output signal from the activation determination unit 32 is at a high level, charges are accumulated in the capacitors C5 and C6.
Even if the output signal from the activation determination unit 32 is inverted from High level to Low level, the first output unit 34 and the second output unit 36
After that, for a while, the start signal VWU1 and the reception permission signal VWU are generated by the electric charges stored in the capacitors C5 and C6.
Continue to output 2 respectively.

Then, the capacitor C5 of the first output section 34
The start signal V has a capacity of at least a transmission time interval of a signal from one data transmission / reception unit 4 on the ground station side.
Since the value is set to a relatively large value so that WU1 can be continuously output, the output of the pilot signal from one data transmission / reception unit 4 constituting the ground station is stopped from the first output unit 34. Accordingly, even if the output signal from the start determination unit 32 is inverted from the high level to the low level, the vehicle transmits and receives the data before the pilot signal is output from the same data transmission / reception unit 4 thereafter. If it does not escape from the communication area where communication with the receiving unit 4 is possible,
The output signal from the activation determination unit 32 becomes High level,
The capacitor C5 is charged with electric charge.
When the activation determination unit 20 enters a communication area where communication with any of the data transmission / reception units 4 constituting the ground station is possible,
Thereafter, until the vehicle exits the communication area, the activation signal VWU1 is continuously output, the power switch 14 is turned on, and the operations of the data transmission / reception unit 16 and the communication control unit 18 are continued.

The capacity of the capacitor C6 of the second output unit 36 is determined only by the reception permission signal V during the transmission time of the interrogation signal or data transmitted from the ground station following the pilot signal.
Since the setting is such that WU2 can be continuously output, the start-up determination unit 32 is output from the second output unit 36 by stopping the output of the pilot signal from one data transmission / reception unit 4 constituting the ground station. Even if the output signal from is inverted from High level to Low level, during the transmission time of the interrogation signal and data transmitted after the pilot signal,
The high-level reception permission signal VWU2 is output from the second output unit 36, and the data received by the reception circuit 16a during that time is transmitted to the communication control unit 1 via the AND gate AND.
8 will be output.

Therefore, according to this embodiment, the transponder enters the communication area of one of the data input / output sections 4 constituting the ground station, and the data transmission / reception section 16 and the communication control section 18 in the transponder. Is activated, then the data input / output unit 4
The data received by the receiving circuit 16a is input to the communication control unit 18 only during the transmission period of the interrogation signal or data transmitted together with the pilot signal from the communication control unit 18. In other periods, the data transmission / reception unit 16 and the communication control unit 16 Even when the unit 18 is activated, the input of the received data to the communication control unit 18 (in other words, the data receiving operation of the transponder) is prohibited.

For this reason, according to the present embodiment, the transponder
Only the transmission data from the data transmission / reception unit 4 of the ground station that has entered the communication area is received, and only the response data corresponding to the data is transmitted. For example, as shown in FIG. 5, the data transmission / reception unit 4 and the antenna 2 on the ground station side
In a system including two ground stations A and B, a transponder receives a pilot signal A from the ground station A, and a start-up determination unit 20 in the transponder determines from the pilot signal A that the ground station A When entry into the communication area is determined and the power switch 14 is turned on by the activation signal VWU1 and the data transmission / reception unit 16 and the communication control unit 18 in the transponder are activated, the data transmission / reception unit 16 and the communication control Part 18
Receives the power supply until the transponder escapes from the communication area and becomes operable, but the AND gate AND
Every time the activation determining unit 20 determines that the ground station A enters the communication area based on the pilot signal,
Since the reception permission signal VWU2 is output from the ground station A only during the time when the interrogation signal (data A1) and the data A3, data A5,.
The communication control unit 18 transmits the response data A corresponding to the data A1, data A3, data A5,.
2, data A4, data A6,...
b.

For this reason, for example, the receiving circuit 1 on the transponder side
In 6a, when reception of data (that is, an interrogation signal or data) transmitted following the pilot signal from the ground station side fails and a response signal or data corresponding to the signal cannot be transmitted, The transponder can receive data transmitted from the ground station at the next transmission timing, and can resume accurate data communication.

On the other hand, in the transponder, the antenna 10,
When external noise is input to the input path of the reception signal from the antenna 10 to the activation determination unit 20, the noise is detected as a reception signal by the detection unit 22, and the detected noise is transmitted to the amplification unit 24. Amplified. Since this noise is larger than a received signal obtained by receiving a pilot signal from the ground station, as in the related art, simply judging the signal level after the amplification will erroneously determine entry into the communication area. Would.

However, in this embodiment, as described above, the pulse signal after the level determination is converted into a pulse signal having a constant pulse width by the determination pulse generator 28, and the pulse signal is converted by the operation of the integrator 30 and the activation determiner 32. When a predetermined number of such pulse signals are continuously generated, entry into the communication area is determined, so that erroneous determination due to such noise can be prevented.

That is, when noise is detected as a received signal by the detector 22, since the noise is larger than the level of the pilot signal, each amplifier circuit in the amplifier 24 is saturated as shown in FIG. As a result, the amplifying unit 24 outputs a signal that changes greatly between positive and negative. Then, the level determination unit 26 compares the signal with the reference voltage VTH1 to generate a pulse signal by comparing the magnitude of the signal with the reference voltage VTH1.
Two pulse signals having a wider pulse width than that at the time of receiving a normal pilot signal are generated. However, in the present embodiment, the determination pulse generator 28 generates a pulse signal having a constant pulse width which becomes High level for a certain time after the rise of the generated pulse signal, and the integration section 30 generates the pulse signal having a constant pulse width. Is integrated by the integrator 30, the input signal level from the integrator 30 to the activation determination unit 32 is equal to the reference voltage VTH2 regardless of the level of the output signal from the amplifier 24. Never go beyond. As a result, the output from the activation determination unit 32 does not become High level due to noise, and the output unit 34
, A drive signal is output from the data transmission / reception unit 16 and the communication control unit 18 to prevent unnecessary activation due to noise.

Therefore, according to the present embodiment, in the start-up determination unit 20 of the responding machine, the vehicle, in other words, the responding machine
It is accurately determined that the vehicle has entered a communication area where communication with any one of the data transmission / reception units 4 of the ground station is possible without being affected by noise, and the data transmission / reception unit 16 and the communication control unit 18 are determined. Can be started and reception can be performed, and the power consumption on the answering machine side can be reduced extremely favorably.

In this embodiment, the transmission speed of the pilot signal is set to the communication speed (100 kHz) for normal data communication.
z) Since the frequency is set to 10 kHz lower than that of the first embodiment, the internal circuit of the start-up determining unit 20 has a slower slew rate than the circuit used for normal data communication, in other words, the responsiveness. The configuration can be made using a low operational amplifier or the like, so that the activation determination unit 20 can be realized relatively inexpensively, and the power consumption of the entire activation determination unit can be suppressed low. Further, since the activation determination unit 20 is configured by an operational amplifier, a comparator, a diode, and the like, it can be easily integrated into a single chip.
Lightening can also be achieved.

In this embodiment, the case where the present invention is applied to a toll road charging system has been described. However, the present invention is applied to a fixed communication device installed on the ground and a mobile body such as an automobile. Needless to say, any communication system can be applied as long as the system communicates with a mobile communication device carried by a user. For example, the present invention may be a communication system that controls an automatic guided vehicle by communication in a factory or the like, or a communication system that connects a portable telephone and a telephone line network fixed on the ground. , Can be applied.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an in-vehicle transponder used in a toll road charging system according to an embodiment.

FIG. 2 is a block diagram illustrating a configuration of a ground station of the toll road charging system according to the embodiment.

FIG. 3 is an electric circuit diagram illustrating a configuration of an activation determining unit provided in the transponder of the embodiment.

FIG. 4 is a time chart for explaining an operation when the activation determination unit of the embodiment receives a pilot signal from a ground station.

FIG. 5 is a time chart for explaining the activation and reception operations of the transponder when the data transmission / reception units of the ground station are two in the toll road charging system of the embodiment.

FIG. 6 is a time chart illustrating an operation when noise is input from the outside in the activation determination unit of the embodiment.

FIG. 7 is a time chart for explaining a start-up of a transponder and a communication operation thereof in a conventional mobile communication system.

[Explanation of symbols]

2-1 to 2-n antenna (ground station side) 4-1 to 4-n data transmission / reception unit (ground station side: fixed communication means) 6 communication control unit (transmission timing control means) 8 billing Device 10: Antenna (responder side) 12: Power supply unit (responder side) 14: Power switch (responder side) 16: Data transmission / reception unit (responder side: mobile communication means) 16a: Receiving circuit 16b: Transmission Circuit AND AND gate 18 Communication control unit (responder side) 20 Start-up determination unit (responder side: determination unit) 22 Detection unit 24 Amplification unit (signal processing unit) 26 Level determination unit (level determination) Means) 28 determination pulse generation unit (determination pulse generation unit) 30 integration unit (integration unit) 32 startup activation unit (activation determination unit) 34 first output circuit (activation unit) 36 second output circuit (reception) Time limit means)

Claims (2)

(57) [Claims] 1. A pilot signal for activating a mobile communication unit mounted on a mobile unit and a response signal transmitted from the mobile communication unit are provided in communication areas obtained by dividing a region through which the mobile unit passes into a plurality of areas. And a plurality of fixed communication units that perform data communication with the mobile communication unit that has transmitted the response signal when the response signal is received after the transmission of the link signal. Means, and a ground station comprising transmission timing control means for executing the transmission of the link signal and the data from each of the fixed communication means in a time-division manner, provided in the mobile unit, and transmitted from the fixed communication means. Mobile communication means for receiving an interrogation signal and data, and transmitting a response signal or data corresponding to the received signal; Receiving the door signal when the pilot signal is above a predetermined level,
Determining means for determining that the moving object has entered the communication area; and activation means for activating the mobile communication means when the determining means determines that the moving object has entered the communication area. And a transponder comprising: a mobile communication system comprising: the fixed communication unit configured to transmit a communication signal to which the pilot signal is added before data to be transmitted during the data communication. In the transponder, when the determining means receives the pilot signal and determines that the mobile body has entered the communication area, the mobile station moves for a predetermined time after which the fixed communication means transmits the interrogation signal or data. Receiving means for permitting the receiving operation of the communication means, and after a predetermined time elapse, providing a receiving time limiting means for inhibiting the receiving operation of the mobile communication means. Moving body communication system. 2. The mobile communication system according to claim 1, wherein each of the fixed communication means constituting a ground station transmits a carrier for starting a predetermined number of times at a predetermined time interval as the pilot signal. The determining means comprises: a signal processing means for detecting and amplifying the starting carrier; and comparing a magnitude of an output signal from the signal processing means with a reference value for level determination, to determine a level of the starting carrier. Level determining means for generating a pulse signal having a corresponding pulse width; determining pulse generating means for converting the pulse signal generated by the level determining means into a pulse signal for starting determination having a constant pulse width; Integrating means for integrating the pulse signal output from the generating means; and when the moving object enters the communication area when the integrated value of the integrating means is equal to or greater than a reference value for starting determination. Mobile communication system, comprising the, and initiation determining means.