JPH09148970A - Magnetic communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong a communication distance by optimizing the balance between the transmission level of power and the reception level of a response signal. SOLUTION: The resonance frequency f0 of a transmission/reception circuit 23 is decided by the inductances and capacity of a coil 20 and capacitors 21 and 22. When power modulated into a frequency f1 is transmitted to a portable- side transmitter/receiver 12 from a power supply-side transmitter/receiver 24 with an electromagnetic induction signal, the transmitter/receiver I2 transmits the response signal which is frequency-modulated with the frequencies f1 and f2 with the electromagnetic induction signal. At that time, respective element constants are set so that a frequency fo' becomes the middle of the frequencies f1 and f2. When the sharpness of resonance in the circuit 23 level of the frequency f2 increases. Thus, the communication distance which the transmitter/ receiver 2 can receive the response signal which the transmitter/receiver 12 transmits can be prolonged compared to the conventional one by the increase amount of the reception level of the frequency f2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitter / receiver of a power supply side when the transmitter / receiver of the power supply side transmits a power modulated by a frequency f1 to the transmitter / receiver of the power supply by an electromagnetic induction signal. For frequencies f1 and f2
The present invention relates to a magnetic communication device for transmitting a response signal frequency-modulated by an electromagnetic induction signal.

[0002]

2. Description of the Related Art FIG. 9 shows a configuration in which such a magnetic communication device is applied to an immobilizer of a vehicle. A control circuit 2 including a microcomputer of a transceiver (power supply side transceiver) 1 provided on the side of an automobile, which is a vehicle, is connected from a battery of the automobile through a power supply circuit (neither is shown).
Power is supplied, and its output terminal is connected to the input terminal of the inverter 3 for transmission.

The output terminal of the inverter 3 is connected to the fixed contact 4a of the changeover switch 4, and the changeover switch 4
The fixed contact 4b of is connected to the ground. The movable contact 4c of the changeover switch 4 has a coil 5 (inductance L
1) and a capacitor 6 (capacitance C1) are connected to earth via a series circuit. The coil 5 is, for example, wound around a core arranged on the back side of a handlebar bracket of an automobile door, or arranged in a loop shape on a peripheral edge portion (not shown) of a door mirror.

Further, the output terminal of the control circuit 2 is connected to the switching signal input terminal of the changeover switch 4, and the control circuit 2 gives the changeover control signal to the changeover switch 4 so that the movable contact 4c is fixed. 4a or 4b
It is designed to control switching so that it is connected to the side.

The capacitor 6 includes a capacitor 7 (capacitance C
2) and the series circuit of the diode 8a are connected in parallel. A reverse diode 8b is connected in parallel to the diode 8a, and a common connection point of the capacitor 7 and the diode 8b is connected to the input terminal of the control circuit 2 via the series circuit of the capacitor 9 and the receiving amplifier 10. It is connected to the. The coil 5, the capacitors 6 and 7, and the diodes 8a and 8b form a transmission / reception circuit 11.

On the other hand, both terminals of the coil 13 of the key 12 which is a portable transceiver are connected to the input terminals of the charging circuit 14, and the output terminals of the charging circuit 14 are the power input of the control circuit 15 including a microcomputer or the like. It is connected to the terminal and is also connected to the ground via the smoothing capacitor 16. The two output terminals of the control circuit 15 are connected to both ends of the coil 13.

In the above structure, the resonance frequency f0 of the transmitter / receiver circuit 11 of the transmitter / receiver 1 is equal to the coil 5 and the capacitor 6
It is determined by the following equations by the respective inductances and capacitances of 7 and 7.

(Equation 1) When the control circuit 2 does not give the changeover control signal to the changeover switch 4 (provides the low level signal), the movable contact 4c is connected to the fixed contact 4a side, and the transceiver 1 is in the transmitting state. Electric power frequency-modulated at the frequency f1 is transmitted as an electromagnetic induction signal. After that, a high-level changeover control signal is given to the changeover switch 4 so that the movable contact 4c is connected to the fixed contact 4b so that the transceiver 1 is kept in a receiving state for a certain period of time.
The operation of waiting for the reception of the response signal from is repeated.

When the coil 13 is brought close to the coil 5 of the transceiver 1, the key 12 receives the electric power transmitted as an electromagnetic induction signal via the coil 13. Then, the charging circuit 14 is charged with the electric power, and the stabilized power is supplied to the power input terminal of the control circuit 15 via the capacitor 16. Then, the control circuit 15 starts the processing, and the I
When the D code data is read, the data "1,0"
The frequency-modulated signal whose frequency changes to f1 and f2 in response to is transmitted as a response signal to the transceiver 1 via the coil 13.

When the response signal is transmitted from the key 12, the control circuit 2 of the transceiver 1 demodulates the ID code and compares it with the ID code stored in the internal ROM (not shown). If the two ID codes match, processing such as starting an engine (not shown) of the automobile is performed.

[0010]

However, in such a magnetic communication device, the resonance frequency f0 of the transmission / reception circuit 11 is set.
Is set so that f0 = f1 according to the frequency f1 at the time of power transmission. Therefore, when a response signal whose frequency changes to f1 and f2 is transmitted from the key 12,
Since the reception level of the frequency f2 is out of the resonance point, it falls below the reception level of the frequency f1 (see FIG. 10). Therefore, even if the sharpness of resonance of the transmitter / receiver circuit 11, so-called Q, is increased to increase the power transmission distance from the transmitter / receiver 1, the receiver sensitivity of the transmitter / receiver 1 is defined by the receiver sensitivity of the frequency f2. Communication distance will be shortened.

The present invention has been made to solve the above problems, and
It is an object of the present invention to provide a magnetic communication device capable of increasing the communication distance by optimizing the balance between the power transmission level and the response signal reception level.

[0012]

In order to achieve the above object, in the magnetic communication apparatus according to claim 1, the power, which is frequency-modulated by the frequency f1 from the power supply side transceiver to the portable side transceiver, is generated by the electromagnetic induction signal. When the portable side transceiver transmits a response signal frequency-modulated at frequencies f1 and f2 to the power supply side transceiver by an electromagnetic induction signal when transmitted, the resonance frequency of the transceiver circuit of the power supply side transceiver is , (F1 + f2) / 2 are set.

According to another aspect of the magnetic communication apparatus of the present invention, when the power supply side transceiver transmits to the portable side transceiver the power frequency-modulated at the frequency f1 by an electromagnetic induction signal, the portable side transceiver transmits and receives the power supply side transceiver. Which transmits a response signal frequency-modulated at frequencies f1 and f2 to the machine by an electromagnetic induction signal, the resonance frequency of the transceiver circuit of the power supply side transceiver is set to f1 at the time of power transmission,
When the response signal is received, it is set to (f1 + f2) / 2.

In this case, the transmitter / receiver circuit of the power supply side transmitter / receiver may be provided with a dumping means for reducing the sharpness of resonance when receiving the response signal (claim 3). Further, the transmission / reception circuit of the power supply side transceiver may be configured to switch the resonance frequency and the sharpness of resonance using a semiconductor switching element (claim 4).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment in which the present invention is applied to an immobilizer for an automobile, which is a vehicle, will now be described with reference to FIG.
This will be described with reference to FIG. The same parts as those in FIG. 9 are designated by the same reference numerals and the description thereof will be omitted. Only different parts will be described below. In FIG. 1 showing the electrical configuration, the coil 5, the capacitors 6 and 7 of the transceiver 1 in FIG. 9 are replaced with the coil 20 (inductance L2) and the capacitors 21 and 22 (capacitances C3 and C4), respectively. ,
A transmitter / receiver 24, which is a power supply side transmitter / receiver having a transmitter / receiver circuit 23, is configured. In addition, key 1 which is a transceiver on the mobile side
The configuration of 2 is the same as that of FIG.

Next, the operation of this embodiment will be described. The transmission / reception operation of this embodiment is similar to the operation of the conventional transceiver 1 and the key 12 shown in FIG. 9, but in the above configuration, the resonance frequency f0 ′ of the transmission / reception circuit 23 is equal to the coil 2
0 and the respective inductances and capacities of the capacitors 21 and 22 are determined by the following equation.

(Equation 2) The constant of each element is set so that the resonance frequency f0 ′ is an intermediate frequency between the frequencies f1 and f2 transmitted by the key 12 as a frequency modulation signal, that is, (f1 + f2) / 2. For example, if the frequency f1 is 130 KHz and the frequency f2 is 119 KH, the frequency difference between the two is 11 KH.
z.

Conventionally, the resonance frequency f0 (130 KHz)
The frequency difference of the frequency f2 with respect to is 11 KHz,
In the case of the present embodiment, the resonance frequency f0 ′ = (119 + 13
Frequency f1 for 0) / 2 KHz = 124.5 KHz
Alternatively, the frequency difference of f2 is 5.5 KHz (Fig. 2
reference).

Therefore, the sharpness Q of resonance between the transmission / reception circuit 11 of the conventional example and the transmission / reception circuit 23 of the present embodiment is substantially the same (actually, the resonance frequency slightly changes by 5.5 KHz). Then, the frequency f1 in this embodiment is
Is the frequency f1 (= f0) in the conventional example.
The reception level of the frequency f2 in the present embodiment is slightly lower than the reception level of the conventional example.
Significantly higher than the reception level of. Therefore, key 12
The distance at which the transceiver 24 can receive the response signal transmitted by
That is, the communication distance becomes longer than in the conventional case by the increase in the reception level of the frequency f2.

As described above, according to the present embodiment, when the transmitter / receiver 24 transmits the frequency-modulated power at the frequency f1 to the key 12 by the electromagnetic induction signal, the key 12 sends the transmitter / receiver 24 the frequency f1. And a response signal frequency-modulated by f2 is transmitted by an electromagnetic induction signal, the resonance frequency f0 ′ of the transceiver circuit 23 of the transceiver 24 is set to (f
1 + f2) / 2 is set, so frequency f1 and frequency f
It is possible to balance the reception levels of the two signals and make them equal, and it is possible to lengthen the communication distance between the two.

3 to 5 show a second embodiment of the present invention. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. Only different parts will be described below. In FIG. 3 showing the electrical configuration, the capacitors 21 and 22 of the transceiver 24 shown in FIG.
(Capacities C6 and C7). The common connection point of the coil 20 and the capacitor 25 and the capacitor 2
A relay switch 27a of the relay 27 is inserted between the relay switch 27 and the switch 6.

The exciting coil 27b of the relay 27 is
One terminal thereof is connected to the power source Vcc, and the other terminal is connected via the inverter 28 to the control signal input terminal of the changeover switch 4, that is, the output terminal of the control circuit 2.
Thus, a transmitter / receiver 30 as a power supply side transmitter / receiver having the transmitter / receiver circuit 29 is configured. The structure of the key 12 which is a portable transceiver is the same as that of the first embodiment.

Next, the operation of the second embodiment will be described with reference to FIGS. 4 and 5. Similar to the first embodiment, the control circuit 2
Does not give a changeover control signal to the changeover switch 4 (provides a low level signal) when transmitting the electric power frequency-modulated at the frequency f1 to the key 12 as an electromagnetic induction signal. The output terminal is at a high level, the exciting coil 27b of the relay 27 is not energized, and the relay switch 27a is turned off. Therefore,
The resonance frequency ft0 of the transmission / reception circuit 29 at the time of transmission is given by the following equation.

(Equation 3) Each circuit constant is determined so that the resonance frequency ft0 becomes equal to the frequency f1 (see FIG. 4).

Then, the control circuit 2 gives the changeover control signal to the changeover switch 4 in the reception state waiting for the reception of the response signal from the key 12, but at this time, the inverter 2
The output terminal of 8 becomes low level, the exciting coil 27b of the relay 27 is energized, and the relay switch 27a is turned on. Therefore, the resonance frequency fr0 of the transmission / reception circuit 29 at the time of reception is as follows.

(Equation 4) The resonance frequency fr0 is equal to the frequency (f1 + f
Each circuit constant is determined so as to be equal to 2) / 2 (see FIG. 5).

Therefore, according to the second embodiment, the same effect as that of the first embodiment can be obtained, and in particular, as shown in FIGS. 4 and 5, the resonance frequency f at the time of transmission and reception of the transmission / reception circuit 29 is obtained.
Since t0 and fr0 are switched to f1 and (f1 + f2) / 2, respectively, it is possible to switch the resonance frequencies of the transceiver 30 at the time of transmission and at the time of reception so as to be optimal.

FIGS. 6 and 7 show a third embodiment of the present invention. The same parts as those of the second embodiment are designated by the same reference numerals and the description thereof will be omitted. Only different parts will be described below. In FIG. 6 showing the electrical configuration, a series circuit of a relay switch 31a of a relay 31 and a resistor 32 (resistance value R) is connected to both ends of the coil 20 in the configuration of the second embodiment shown in FIG. .

In the exciting coil 31b of the relay 31,
One terminal is connected to the power supply Vcc, and the other terminal is connected to the output terminal of the control circuit 2 via the inverter 33, similarly to the exciting coil 27b. In addition, the resistor 32, the relay 31, and the inverter 33 constitute dump means,
Thus, a transmitter / receiver 35 as a power supply side transmitter / receiver having the transmitter / receiver circuit 34 is configured. The structure of the key 12 which is a portable transceiver is the same as that of the first embodiment.

Next, the operation of the third embodiment will be described. The control circuit 2 transmits the electric power frequency-modulated at the frequency f1 to the key 12 as the electromagnetic induction signal at the resonance frequency ft0 as in the second embodiment. At this time, the output terminal of the inverter 33 becomes high level and the relay 3
The first excitation coil 31b is not energized, and the relay switch 31a is turned off.

When the control circuit 2 is in the reception state waiting for the reception of the response signal from the key 12, the control circuit 2 is also in the second state.
As in the embodiment, the signal is received at the resonance frequency fr0. Then, the output terminal of the inverter 33 becomes low level, the exciting coil 31b of the relay 31 is energized, the relay switch 31a is turned on, and the coil 32 has a resistor 32.
Are connected in parallel.

At this time, comparing the sharpness Q1 of the resonance of the transmitting / receiving circuit 34 at the time of reception with the sharpness Q of the resonance of the transmitting / receiving circuit 29 of the second embodiment at the time of reception,
When the coil 20 has a resistance having an equivalent resistance value r, the admittance Y of the transmission / reception circuit 29 is equal to the equivalent resistance value r.
The smaller is, the larger is. Further, in the admittance Y1 of the transmission / reception circuit 34, since the resistance 32 is connected in parallel to the coil 20, the equivalent resistance value r decreases, and Y
1> Y.

Therefore, when the resonance sharpnesses Q1 and Q are compared by the ratio of the voltage values E1 and E when the current values at resonance are both i, Q1 / Q = E1 / E = (i / Y1) / (I / Y) = Y /
Y1 <1 and the resonance sharpness Q1 becomes smaller (duller) than Q. Thus, by making the sharpness Q1 of the resonance at the time of reception dull, the peak at the resonance frequency (f1 + f2) / 2 in the curve of the reception level shown in FIG. The reception level of f2 is higher than the reception level of the second embodiment shown by the broken line.

As described above, according to the third embodiment, the transceiver circuit 34 connects the resistor 32 to the coil 20 in parallel when the response signal is received from the key 12, so that the resonance sharpness Q1 is set to the second value. Since the resonance sharpness Q is set to be slower than that in the embodiment, the reception level of the frequencies f1 and f2 can be increased and the communication distance between the transceiver 35 and the key 12 can be made longer.

The present invention is not limited to the embodiment described above and shown in the drawings, and the following modifications or extensions are possible. In the first embodiment, by connecting resistors in parallel to both ends of the coil 20, the transmitter / receiver circuit 2
The sharpness Q of resonance of 3 may be adjusted. For example, as shown by the solid line in FIG. 8, the reception sensitivities of the frequencies f1 and f2 are set to −3.
When set to dB, f0 = 124.5 KHz, f1-f
Since 2 = 11 KHz, the resonance sharpness Q is Q = 12
It is represented by 4.5 / 11 and becomes about 11.3. On the other hand, in the conventional case, as indicated by the broken line, f0 = f1 = 13
When the reception sensitivity of f2 is set to -3 dB, the sharpness Q of resonance is represented by Q = 130 / (11 × 2) and is about 6. Therefore, the resonance frequency f0 is (f1 + f
By setting 2) / 2, the sharpness Q of the resonance can be set higher, so that it is possible to further increase the reception sensitivity and further increase the communication distance.

In the second embodiment, the inductance of the coil 20 may be changed to change the resonance frequency.
In the third embodiment, a semiconductor switching element such as a triac may be used in place of the relays 27 and 31, and ON / OFF control may be performed by giving a changeover control signal given to the changeover switch 4 by the control circuit 2 as a gate signal. With such a configuration, the transceiver 35 can be made compact. Not limited to immobilizers,
It may be applied to a door lock system or the like. Not limited to automobiles, it can be applied to vehicles in general.

[0034]

Since the present invention is as described above,
The following effects are obtained. According to the magnetic communication device of claim 1, the resonance frequency of the transmission / reception circuit of the power supply side transceiver is (f1 + f2) / 2 with respect to the frequencies f1 and f2 of the response signal of the portable side transceiver which is a frequency modulation signal. Since it is set to, the communication distance between the two can be lengthened.

According to another aspect of the magnetic communication device of the present invention, the resonance frequency of the transmission / reception circuit of the transceiver on the power supply side is set to f1 during power transmission and (f1 + f) during response signal reception.
Since it is set to 2) / 2, the resonance frequency at the time of transmission and reception of the power-side transceiver can be switched to be optimum.

According to another aspect of the magnetic communication device of the present invention, the dumping means provided in the transmission / reception circuit of the transceiver on the power supply side reduces the sharpness of resonance when the response signal is received. It is possible to further increase the communication distance between the power supply side transceiver and the portable side transceiver.

According to another aspect of the magnetic communication device of the present invention, the transceiver circuit of the power-supply-side transceiver switches the resonance frequency and the sharpness of the resonance by using the semiconductor switching element, so that the power-supply-side transceiver is made compact. can do.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a reception level with respect to a frequency of a transceiver.

FIG. 3 is a view corresponding to FIG. 1, showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a level at the time of transmission with respect to a frequency of a transceiver.

FIG. 5 is a diagram showing a level at the time of reception with respect to a frequency of a transceiver.

FIG. 6 is a view corresponding to FIG. 1, showing a third embodiment of the present invention.

FIG. 7 is a diagram corresponding to FIG. 2;

FIG. 8 is a view corresponding to FIG. 2 showing a modified example.

FIG. 9 is a view corresponding to FIG. 1 showing a conventional technique.

FIG. 10 is a diagram corresponding to FIG. 2;

[Explanation of symbols]

12 is a key (portable transceiver), 23 is a transceiver circuit, 2
4 is a transceiver (power supply side transceiver), 29 is a transceiver circuit, 30 is a transceiver (power supply side transceiver), 31 is a relay (dump means), 32 is a resistor (dump means), 33
Is an inverter (dump means), 34 is a transmission / reception circuit, and 35
Indicates a transceiver (a transceiver on the power supply side).

Claims (4)

[Claims] 1. When the power supply side transceiver transmits to the portable side transceiver the frequency-modulated power at the frequency f1 by an electromagnetic induction signal, the portable side transceiver transmits the frequency f1 and the frequency f1 to the portable side transceiver. In a magnetic communication device for transmitting a response signal frequency-modulated by f2 by an electromagnetic induction signal, a resonance frequency of a transmission / reception circuit of the power supply side transceiver is
A magnetic communication device characterized by being set to (f1 + f2) / 2. 2. When the power supply side transceiver transmits to the portable side transceiver the frequency-modulated power at the frequency f1 by an electromagnetic induction signal, the portable side transceiver transmits the frequency f1 and the frequency f1 to the portable side transceiver. In a magnetic communication device for transmitting a response signal frequency-modulated by f2 by an electromagnetic induction signal, a resonance frequency of a transmission / reception circuit of the power supply side transceiver is
A magnetic communication device characterized in that it is set to f1 when transmitting power and (f1 + f2) / 2 when receiving a response signal. 3. The magnetic communication device according to claim 2, wherein the transmission / reception circuit of the power supply side transceiver is provided with dumping means for reducing the sharpness of resonance when receiving a response signal. 4. The magnetic communication device according to claim 3, wherein the transmission / reception circuit of the power supply side transceiver is configured to switch the resonance frequency and the sharpness of resonance by using a semiconductor switching element.