JP4999973B2 - Wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication system for realizing a smart keyless entry system or the like by performing communication between an in-vehicle device having a wireless communication function mounted on a vehicle and a portable device having a wireless communication function carried by a vehicle user. It is about.

  There is known a keyless entry system that enables locking and unlocking of an automobile door by remote operation from a portable wireless device carried by an automobile user. A smart entry system that locks and unlocks a door without operating a portable wireless device is also known.

  In Patent Document 1, in a keyless entry system having an in-vehicle communication device (hereinafter referred to as an in-vehicle device) and a portable wireless device (hereinafter referred to as a portable device), a request signal by LF (Low Frequency) communication from the in-vehicle device. Thus, a method of avoiding communication failure due to jamming radio waves by switching the frequency (channel) of RF (Radio Frequency) communication returned from the portable device to the vehicle-mounted device is shown.

JP 2008-255679 A

By the way, when LF communication is performed between an in-vehicle communication device and a portable wireless device of an automobile, if the resonance frequency of the transmission / reception circuit fluctuates with respect to the carrier frequency, the amplitude of the LF reception signal fluctuates. If the amplitude fluctuation of the received signal exceeds the allowable range, the signal cannot be demodulated and communication is impossible.
As countermeasures, there is a method to reduce the amplitude fluctuation by lowering the Q of the transmission / reception system or suppressing the fluctuation range of the resonance frequency. However, if the Q of the transmission / reception system is lowered, the communication distance becomes shorter and the fluctuation range of the resonance frequency is suppressed. In addition, if high-precision parts are used and the resonance frequency is adjusted, the cost increases.

  The present invention has been made in view of such a background, and it is an object of the present invention to provide a radio communication system that ensures a good LF reception performance by preventing a decrease in communication performance due to the influence of resonance frequency fluctuations. .

  A wireless communication system according to the present invention is a wireless communication system including an in-vehicle device having a wireless communication function mounted on a vehicle and a portable device having a wireless communication function carried by a vehicle user. Includes a CPU, a memory for storing an authentication code, a transmission circuit for transmitting an electric field strength measurement signal and an authentication request signal, and a reception circuit for receiving an authentication response signal. A memory for storing the signal, a receiving circuit for receiving the signal for measuring the electric field strength and the authentication request signal, a transmitting circuit for transmitting the authentication response signal, and an electric field strength measuring unit for measuring the electric field strength of the signal for measuring the electric field strength. The reception circuit of the portable device has a resonance circuit that switches the resonance frequency in multiple stages, and the portable device switches the resonance frequency of the resonance circuit with the electric field strength measurement signal transmitted from the in-vehicle device. While receiving and measuring the electric field strength at each stage, after switching the resonance circuit to the resonance frequency when the electric field strength becomes the maximum value among the measured electric field strengths, receiving the authentication request signal and receiving the authentication response signal The data is transmitted to the in-vehicle device.

  According to the present invention, in a wireless communication system such as a smart keyless system, the resonance frequency is reduced due to secular variation of circuit element constants used in a transmission circuit of an in-vehicle device and a reception circuit of a portable device, and variations due to tolerances. Even when it fluctuates, it is possible to automatically realize a good LF communication state, and use of high-precision components and precise resonance frequency adjustment are unnecessary.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic block diagram which applied the radio | wireless communications system which concerns on Embodiment 1 of this invention to the smart keyless entry system. It is a circuit block diagram of the vehicle equipment in Embodiment 1 of this invention. It is a circuit block diagram of the portable machine in Embodiment 1 of this invention. It is detail drawing of the LF receiver circuit of the portable device in Embodiment 1 of this invention. It is a flowchart explaining operation | movement of the smart keyless entry system in the radio | wireless communications system which concerns on Embodiment 1 of this invention. It is a time chart explaining operation | movement of the smart keyless entry system in the radio | wireless communications system which concerns on Embodiment 1 of this invention.

Embodiment 1 FIG.
Hereinafter, a smart keyless entry system as a wireless communication system according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram showing a configuration of a smart keyless entry system according to an embodiment of the present invention. As shown in FIG. 1, a smart keyless entry system includes a wireless communication device 1 (hereinafter referred to as an in-vehicle device 1) mounted on an automobile 100 and a wireless communication device 2 (hereinafter referred to as an on-vehicle device 1) carried by a user 200 of the vehicle. (Referred to as portable device 2). The vehicle-mounted device 1 is electrically connected to a device 4 (hereinafter referred to as a control device 4) that controls the ignition switch of the automobile 100 and controls the locking and unlocking of the door.

  The in-vehicle device 1 is connected to the LF transmitting antennas 14 a and 14 b provided on the door of the automobile 100 and the LF transmitting antenna 14 c provided between the front and rear seats in the vehicle interior, and further receives an RF signal from the portable device 2. The request antennas 16a and 16b provided on the receiving antenna 15 and the door knob of the automobile 100 are connected.

  In the smart keyless entry system according to the embodiment of the present invention, the vehicle-mounted device 1 receives a signal sent from the portable device 2, and the vehicle-mounted device 1 determines whether or not the ignition operation is permitted or prohibited according to the content of the received signal. Then, the controller 4 is instructed to permit or prohibit the ignition operation. The in-vehicle device 1 determines whether the door is locked or unlocked according to the content of the received signal, and instructs the control device 4 to lock or unlock the door. Also, the in-vehicle device 1 determines whether the portable device 2 is within a communicable range with the in-vehicle device 1 according to the content of the received signal, and allows the control device 4 to permit / prohibit the alarm buzzer sounding and the warning lamp. Instruct to turn on / off.

  In the embodiment described below, communication from the in-vehicle device 1 to the portable device 2 uses a signal modulated using an LF (Low Frequency) communication method. Further, communication from the portable device 2 to the portable device 1 uses a signal that has been modulated using an RF (Radio Frequency) communication method.

  FIG. 2 shows a circuit configuration of the in-vehicle device 1 of the wireless communication system as an embodiment of the present invention. The in-vehicle device 1 includes a CPU 10, a memory 11 including an authentication code 110 and a ROM or RAM that stores an execution program, an LF transmission circuit 12 that transmits an electric field strength measurement signal and an authentication request signal, and an authentication response signal from the portable device 2 And an SW signal input circuit 17 for inputting signals from the request SWs 16a and 16b. The LF transmission antennas 14 a, 14 b, and 14 c are connected to the LF transmission circuit 12 of the in-vehicle device 1, the RF reception antenna 15 is connected to the RF reception circuit 13, and the request SWs 16 a and 16 b are connected to the SW signal input circuit 17.

  The CPU 10 performs integrated control of the in-vehicle device 1 and implements various functions by executing programs stored in the memory 11. The memory 11 stores an authentication code 110 for authenticating data transmitted from the portable device 2.

The LF transmission circuit 12 includes a modulation circuit 121 that generates a transmission signal obtained by modulating a signal output from the CPU 10 with a sine wave carrier wave in the LF frequency band, and an amplification circuit 122 that amplifies the transmission signal. LF transmitting antennas 14a, 14b, and 14c that transmit to the atmosphere are connected.
The LF transmission antenna 14c is used for transmission into the vehicle interior, and the LF transmission antennas 14a and 14b are used for transmission outside the vehicle.

  The RF reception circuit 13 is connected to an RF reception antenna 15 that receives a radio signal in the atmosphere, and is generated by demodulating the reception signal and an amplification circuit 131 that amplifies the reception signal input from the RF reception antenna 15. The demodulating circuit 132 outputs a demodulated signal to the CPU 10.

FIG. 3 shows a circuit configuration of the portable device 2 of the wireless communication system as an embodiment of the present invention. The portable device 2 includes a CPU 20, an input circuit 21 that detects an operation input such as a switch that serves as a trigger for using the keyless entry function, a memory 22 including a ROM, a RAM, and the like that store an authentication code 220 and a measured electric field strength 221. , An RF transmission circuit 23 that transmits an authentication response signal, an LF reception circuit 24 that receives an electric field strength measurement signal and an authentication request signal transmitted from the vehicle-mounted device 1, an RF transmission antenna 25, an LF reception antenna 26, and an electric field strength measurement An RSSI (Received Signal Strength Indicator) circuit 27, which is an electric field strength measuring unit for measuring the electric field strength of the signal, is configured.
The input circuit 21 is omitted when applied to a smart entry system that locks and unlocks the door without operating the portable device 2.

  The CPU 20 performs integrated control of the portable device 2 and implements various functions by executing programs stored in the memory 22. In the memory 22, an authentication code 220 that is transmitted from the portable device 2 to the in-vehicle device 1 and is necessary for authenticating the portable device 2 in the in-vehicle device 1 is stored in the ROM. Further, the RAM of the memory 22 has a memory area 221 that stores electric field strengths E1, E2, and E3 as electric field strength measurement results.

The RF transmission circuit 23 includes an RF modulation circuit 231 that generates a transmission signal in which a carrier wave in the RF frequency band is modulated by a signal output from the CPU 20, and an amplification circuit 232 that amplifies the transmission signal. Is connected to an RF transmitting antenna 25 for transmitting to the.
The LF reception circuit 24 is connected to an LF reception antenna 26 that receives radio signals in the atmosphere, and is generated by demodulating the reception signal and a resonance circuit 241 that resonates with the reception signal input from the LF reception antenna 26. And an LF demodulation circuit 242 for inputting a demodulated signal to the CPU 20.

The resonance circuit 241 will be specifically described with reference to FIG. 4 showing details of the LF reception circuit 24 of the portable device.
In the resonance circuit 241, capacitors C21, C22, and C23 are connected in parallel to the LF receiving antenna 26. Connection and release of each capacitor is performed by switch circuits SW1, SW2, and the like connected in series to each capacitor in response to a command signal from the CPU 20. It is controlled by turning SW3 ON or OFF.

The LF resonance frequency of the resonance circuit 241 is determined by the connection state of the capacitors C21, C22, and C23. When the capacitor C21 is selected, that is, when only the switch circuit SW1 is turned on, the resonance frequency FC1 is selected, and when the capacitor C22 is selected, that is, when only the switch circuit SW2 is turned on. When the resonance frequency FC2 is selected and the capacitor C23 is selected, that is, when only the switch circuit SW3 is turned on, the resonance frequency FC3 is selected.
Thus, the resonance circuit 241 switches the resonance frequency according to a command signal from the CPU 20 of the portable device.

The input circuit 21 detects an operation input by the vehicle user 200 having the portable device 2 to lock or unlock a door or a trunk, and outputs a signal corresponding to the operation input to the CPU 20.
The RSSI circuit 27 which is an electric field strength measuring unit converts the electric field strength of the received signal inputted from the resonance circuit 241 into an analog voltage signal, detects it, digitizes it, and outputs it to the CPU 20.

Next, in the wireless communication system configured as described above, the specific operation of the smart keyless entry system according to Embodiment 1 of the present invention will be described using the flowchart of FIG. 5 and the timing chart of FIG. To do.
The flow chart of FIG. 5 and the timing chart of FIG. 6 illustrate a case where the vehicle user 200 with the portable device 2 operates the request SW 16a outside the vehicle and tries to unlock the door.

  In FIG. 5, first, when the vehicle user 200 operates the request SW 16a attached to the door knob of the automobile 100, the CPU 10 of the vehicle-mounted device 1 detects the operation signal by the SW signal input circuit 17 (S400: YES). In order to check whether the portable device 2 exists outside the vehicle, the LF transmission circuit 12 is controlled to start transmission of a radio signal (hereinafter referred to as a field strength measurement signal). The electric field strength measurement signal is transmitted from the LF transmission antennas 14a and 14b toward the outside of the vehicle. As shown in FIG. 6A, the signal for measuring the electric field strength is divided into three stages for every predetermined period, and transmitted for a predetermined period. First, the signal 1 for measuring the electric field intensity is transmitted (S401).

  In the portable device 2, the switch circuit SW1 is set to ON, the switch circuit SW2 is set to OFF, and the switch circuit SW3 is set to OFF in order to set the resonance frequency of the resonance circuit 241 to the resonance frequency FC1 in advance according to a command from the CPU 20. S402). When the field strength measurement signal 1 is received by the LF reception antenna 26 and reception is started via the LF reception circuit 24 (S403: YES), the RSSI circuit 27 converts the received signal into an analog signal as shown in FIG. It converts into a voltage signal, the electric field strength is measured, and electric field strength measurement result is made into electric field strength E1 (S404). If the reception of the electric field strength measurement signal 1 is completed (S405: YES), the electric field strength E1 is converted into a digital signal and output to the CPU 20, and only the peak value of the measurement result is stored in the memory area 221 of the memory 22. Is stored as a peak value (S406).

  Subsequently, the vehicle-mounted device 1 transmits the electric field strength measurement signal 2 (S407). The CPU 20 of the portable device 2 sets the switch circuit SW1 to OFF, the switch circuit SW2 to ON, and the switch circuit SW3 to OFF in order to set the resonance frequency of the resonance circuit 241 to the resonance frequency FC2 (S408). The electric field strength measurement signal 2 is received by the LF receiving circuit 24 via the LF receiving antenna 26, and the RSSI circuit 27 converts the received signal into an analog voltage signal as shown in FIG. The electric field strength measurement result is defined as electric field strength E2 (S409). If the reception of the electric field strength measurement signal 2 is completed (S410: YES), the electric field strength E2 is converted into a digital signal and output to the CPU 20, and only the peak value of the measurement result is stored in the memory area 221 of the memory 22. Is stored as a peak value (S411).

  Subsequently, the vehicle-mounted device 1 transmits the electric field strength measurement signal 3 (S412). In order to set the resonance frequency of the resonance circuit 241 to the resonance frequency FC3, the CPU 20 of the portable device 2 sets the switch circuit SW1 to OFF, the switch circuit SW2 to OFF, and the switch circuit SW3 to ON (S413). The electric field strength measurement signal 3 is received by the LF receiving circuit 24 via the LF receiving antenna 26, and the RSSI circuit 27 converts the received signal into an analog voltage signal as shown in FIG. The electric field strength measurement result is defined as electric field strength E3 (S414). If reception of the electric field strength measurement signal 3 is completed (S415: YES), the electric field strength E3 is converted into a digital signal and output to the CPU 20, and only the peak value of the measurement result is stored in the memory area 221 of the memory 22 in the electric field strength E3. Is stored as a peak value (S416).

  Next, it is determined whether or not the electric field strength E1 stored in the memory area 221 of the memory 22 is larger than the electric field strengths E2 and E3 (S417). If larger (S417: YES), the resonance frequency FC1 at the time of measuring the electric field strength E1 is It is determined that the resonance state is optimum, and the switch circuit SW1 is set to ON, the switch circuit SW2 is set to OFF, and the switch circuit SW3 is set to OFF in order to set the resonance frequency of the resonance circuit 241 to the resonance frequency FC1 (S418).

  If the electric field strength E1 of the memory area 221 of the memory 22 is not larger than the electric field strengths E2 and E3 (S417: NO), it is determined whether the electric field strength E2 is larger than the electric field strengths E1 and E3 (S419). S419: YES) In order to determine that the resonance frequency FC2 at the time of measuring the electric field intensity E2 is the optimum resonance state, and to set the resonance frequency of the resonance circuit 241 to the resonance frequency FC2, the switch circuit SW1 is turned off and the switch circuit SW2 is turned on. ON and the switch circuit SW3 are set to OFF (S420).

If the electric field strength E2 of the memory area 221 of the memory 22 is not larger than the electric field strengths E1 and E3 (S419: NO), it is determined that the resonance frequency FC3 at the time of measuring the electric field strength E3 is an optimal resonance state, and the resonance circuit 241 In order to set the resonance frequency to the resonance frequency FC3, the switch circuit SW1 is set to OFF, the switch circuit SW2 is set to OFF, and the switch circuit SW3 is set to ON (S421).
Thus, the electric field strengths E1, E2, and E3 stored in the memory 20 of the portable device 2 are respectively compared, and the state when the highest electric field strength is obtained is determined as the optimum LF signal reception state. When performing LF reception, this resonance frequency is selected and used. For example, if the electric field strength E2 is the highest, the resonance frequency of the receiving circuit is selected as FC2.

  When the optimal LF signal reception state is determined and the resonance frequency of the LF reception circuit is selected, the in-vehicle device 1 transmits an authentication request signal as shown in FIG. 6C (S422). When the portable device 2 receives the authentication request signal from the vehicle-mounted device 1 (S423: YES), the authentication code 220 stored in the memory 22 is used as an authentication response signal via the RF transmission circuit 23 and the RF transmission antenna 25. (S425). If the signal received by the RF receiving antenna 15 of the vehicle-mounted device 1 is input to the CPU 10 via the RF receiving circuit 13 and received as an authentication response signal (S426: YES), the content of the received signal is stored in the memory 11. It is determined whether or not it matches the authentication code 111 (S427). If it matches (S427: YES), a door lock unlocking request is transmitted to the control device 4 (S428), and the door lock unlocking is performed. I do.

  The in-vehicle device 1 determines the specified time when the authentication response signal is not received (S426: NO) or the content of the received signal does not match the authentication code 111 stored in the memory 11 (S427: NO). It is determined whether or not the time has elapsed (S429), and if the specified time has not elapsed (S429: NO), it waits for reception of an authentication response signal (S401). If the specified time has elapsed (S429: YES), the authentication communication is terminated as a communication error.

As described above, by automatically adjusting the resonance frequency of the LF receiving circuit 24 of the portable device 2 to the optimum value, it is possible to continue good LF communication. It is possible to automatically realize a good LF communication state even when the resonance frequency fluctuates due to aging of circuit element constants used in the receiver circuit or variations due to tolerances, and high precision components Use and precise resonance frequency adjustment are unnecessary.
Therefore, the smart keyless performance can be improved by applying the wireless communication system and the wireless communication method to the smart keyless entry system.

In the first embodiment, the LF reception circuit 24, the memory 22, the RF transmission circuit 23, and the RSSI circuit 27 of the portable device 2 are configured outside the CPU 20, but the same effect can be obtained by incorporating them in the CPU 20. It is possible to obtain.
In the first embodiment, the electric field strength measurement signal is transmitted three times at predetermined intervals for each predetermined period, and the resonance frequency of the receiving circuit of the portable device is switched to FC1, FC2, and FC3 during each transmission period. The electric field strength measured during each period is sequentially stored in the memory of the portable device as electric field strengths E1, E2, and E3. However, the number of transmissions of the electric field strength measurement signal is not limited to three times, but two times or more. If it is. However, if the number of times is too large, authentication takes time, so it is desirable that the number is at most five.

1 onboard machine, 2 portable machine,
4 control unit, 10 CPU,
11 memory, 12 LF transmission circuit,
13 RF receiving circuit, 14a LF transmitting antenna,
14b LF transmit antenna, 14c LF transmit antenna,
15 RF receiving antenna, 16a request SW,
16b request SW, 17 SW input circuit,
20 CPU, 21 input circuit,
22 memory, 23 RF transmitter circuit,
24 LF receiver circuit, 25 RF transmit antenna,
26 LF receiving antenna, 27 RSSI circuit,
100 automobile 200 vehicle user 110 authentication code 121 amplification circuit
122 modulation circuit, 131 demodulation circuit,
132 amplifier circuit, 220 authentication code,
221 memory area 231 modulation circuit,
232 amplifier circuit, 241 resonant circuit,
242 Demodulation circuit.

Claims (8)

  A wireless communication system including an in-vehicle device having a wireless communication function mounted on a vehicle and a portable device having a wireless communication function carried by a vehicle user, wherein the in-vehicle device includes a CPU and an authentication code. A memory for storing, a transmission circuit for transmitting an electric field strength measurement signal and an authentication request signal, and a receiving circuit for receiving an authentication response signal, wherein the portable device includes a CPU, a memory for storing an authentication code, A reception circuit that receives the signal for measuring the electric field strength and the authentication request signal; a transmission circuit that transmits the authentication response signal; and an electric field strength measurement unit that measures the electric field strength of the signal for measuring the electric field strength. The reception circuit of the device has a resonance circuit that switches the resonance frequency in multiple stages, and the portable device transmits the electric field strength measurement signal transmitted from the in-vehicle device to the resonance frequency of the resonance circuit. And receiving the authentication request signal after switching the resonance circuit to the resonance frequency at which the electric field strength becomes the maximum value among the measured electric field strengths. And transmitting the authentication response signal to the in-vehicle device.   The wireless communication system according to claim 1, wherein the resonance circuit of the portable device includes a circuit that switches a resonance frequency according to a command signal of a CPU of the portable device.   The wireless communication system according to claim 1, wherein the electric field strength measurement unit is configured using an RSSI (Received Signal Strength Indicator) circuit.   The electric field strength measurement signal transmitted from the in-vehicle device is a LF (Low Frequency) band sine wave, and is transmitted n times (n is an integer of 2 or more) at predetermined intervals for each predetermined period. The resonance frequency of the resonance circuit is switched to n stages, the electric field intensity measurement signal is received, the electric field intensity is measured, and the electric field intensity E1 to En measured at each stage is sequentially stored in the memory of the portable device. The wireless communication system according to any one of claims 1 to 3.   The electric field strengths E1 to En stored in the memory of the portable device are respectively compared, and the state when the highest electric field strength is obtained is determined as the optimum LF signal reception state. The wireless communication system according to claim 4, wherein the resonance frequency is selected and used.   The vehicle-mounted device is connected to a control device that controls locking / unlocking of a door of a vehicle, and transmits a signal instructing locking / unlocking of the door to the control device. The radio | wireless communications system of any one of Claims 1-3.   The in-vehicle device is connected to a control device that controls the sounding of the alarm buzzer and / or the lighting of the warning lamp, and transmits a signal instructing the operation of the alarm buzzer and / or the warning lamp to the control device. The radio communication system according to any one of claims 1 to 3, wherein the radio communication system is configured as described above.   The vehicle-mounted device is connected to a control device that performs control related to an ignition operation of a vehicle, and transmits a signal instructing permission / prohibition of the ignition operation to the control device. Item 4. The wireless communication system according to any one of items 3 to 3.

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