JP2018039378A - On-vehicle communication system, on-vehicle device, and portable machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle communication system, an on-vehicle device, and a portable machine.SOLUTION: An on-vehicle device includes: an on-vehicle side transmission part for alternately transmitting two kinds of detection signals with phases that are mutually different by 180 degrees; an on-vehicle side receiving part for receiving a response signal transmitted from a portable machine in response to the detection signals transmitted by the on-vehicle side transmission part; and a position detection part for detecting a position of the portable machine, on the basis of the response signal received by the on-vehicle side receiving part. The portable machine includes: a portable machine side receiving part for receiving the two kinds of detection signals transmitted from the on-vehicle side transmission part; a subtraction part for subtracting the other from one of the two kinds of detection signals received; a calculation part for calculating signal intensity of the detection signals received by the portable machine side receiving part, on the basis of the signal obtained from the subtraction part by subtraction; and a portable machine side transmission part for transmitting a response signal containing information of the signal intensity calculated by the calculation part.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an in-vehicle communication system, an in-vehicle device, and a portable device.

  A keyless entry system and a smart entry system have been put to practical use as door lock systems that can lock and unlock a vehicle door without using a mechanical key. In a keyless entry system, when an occupant performs an operation on an operation unit (a lock button or an unlock button) provided in a portable device, a control signal is transmitted from the portable device to the in-vehicle device, and the in-vehicle device that has received the control signal Thus, locking or unlocking of the vehicle door is controlled. In the smart entry system, when an occupant carrying a portable device operates a request switch provided on the door handle of the vehicle, wireless communication is performed between the portable device and the in-vehicle device, and the vehicle door is Control related to locking or unlocking is performed.

  In such a keyless entry system and smart entry system, the position of the portable device is determined when the vehicle door is opened and closed, and if the portable device is present in the vehicle, the engine is permitted to start. In addition, after a certain time (for example, 30 seconds) has elapsed since the engine was started, the portable device is searched, and if the portable device is not detected in the vehicle, a notification sound or a notification is displayed on the vehicle display to inform the driver of the portable device. A system for notifying the non-portable person has also been proposed.

Japanese Patent No. 5596927

  In the keyless entry system and the smart entry system described above, when environmental noise is included in a signal transmitted and received between the in-vehicle device and the portable device, the position of the portable device may be erroneously determined.

  For this reason, technology that reduces environmental noise by subtracting environmental noise measured in advance when environmental noise is measured in advance on a portable device and a detection signal is received from an in-vehicle device Has been proposed.

  However, since environmental noise changes according to time and place, the conventional configuration for measuring environmental noise in advance in a portable device needs to periodically perform an operation for measuring environmental noise. There is a problem that the lifetime is shortened.

  The present invention has been made in view of such circumstances, and in-vehicle communication capable of removing environmental noise from a detection signal received by a portable device without periodically measuring the environmental noise by the portable device. An object is to provide a system, an in-vehicle device, and a portable device.

  An in-vehicle communication system according to an aspect of the present invention includes an in-vehicle device mounted on a vehicle and a portable device capable of wireless communication with the in-vehicle device, and wireless communication between the in-vehicle device and the portable device. The vehicle-mounted communication system detects the position of the portable device by the vehicle-mounted device, and the vehicle-mounted device alternately transmits two types of detection signals whose phases are different from each other by 180 degrees. And an on-vehicle side receiving unit that receives a response signal transmitted from the portable device in response to the detection signal transmitted by the on-vehicle side transmitting unit, and the portable device based on the response signal received by the on-vehicle side receiving unit. A position detection unit that detects the position of the machine, and the portable device receives the two types of detection signals transmitted from the in-vehicle side transmission unit, and the received two types of detection signals. Subtractor that subtracts one from the other A calculation unit for calculating the signal strength of the detection signal received by the portable device-side receiving unit based on the signal obtained by subtraction by the subtraction unit, and a response signal including information on the signal strength calculated by the calculation unit And a portable device side transmission unit.

  An in-vehicle device according to an aspect of the present invention is an in-vehicle device that detects the position of the portable device by performing wireless communication with the portable device, and receives two types of detection signals that are 180 degrees out of phase with each other. A transmitter that alternately transmits, a receiver that receives a response signal transmitted from the portable device with respect to the detection signal transmitted by the transmitter, and the portable device based on the response signal received by the receiver A position detector for detecting the position of the machine.

  A portable device according to one aspect of the present invention is a portable device that performs wireless communication with an in-vehicle device, and a reception unit that receives two types of detection signals that are alternately transmitted from the in-vehicle device and that are 180 degrees out of phase with each other. A subtractor that subtracts one of the two types of received detection signals from the other; a calculator that calculates the signal strength of the detection signal received by the receiver based on a signal obtained by subtraction by the subtractor; A transmission unit that transmits a response signal including information on the signal strength calculated by the calculation unit.

  According to the present application, the environmental noise can be removed from the received detection signal from the in-vehicle device without periodically measuring the environmental noise with the portable device.

It is a mimetic diagram explaining the schematic structure of the in-vehicle control system concerning this embodiment. It is a block diagram explaining the internal structure of a vehicle-mounted apparatus. It is a block diagram explaining the internal structure of a portable device. It is a block diagram which shows the structural example of the LF transmission part with which a vehicle-mounted apparatus is provided. It is explanatory drawing explaining the LF signal which an in-vehicle apparatus and a portable device transmit / receive. It is a flowchart explaining the procedure of the process which a portable machine performs.

  Embodiments of the present invention will be listed and described. Moreover, you may combine arbitrarily at least one part of embodiment described below.

  An in-vehicle communication system according to one aspect of the present application includes an in-vehicle device mounted on a vehicle and a portable device capable of wireless communication with the in-vehicle device, and performs wireless communication between the in-vehicle device and the portable device. An in-vehicle communication system that detects the position of the portable device by the in-vehicle device, wherein the in-vehicle device alternately transmits two types of detection signals that are 180 degrees out of phase with each other. An in-vehicle side receiving unit that receives a response signal transmitted from the portable device in response to the detection signal transmitted by the in-vehicle side transmitting unit, and the portable device based on the response signal received by the in-vehicle side receiving unit A position detection unit that detects the position of the mobile device, wherein the portable device receives the two types of detection signals transmitted from the in-vehicle side transmission unit, and one of the two types of received detection signals A subtractor that subtracts the other from Based on the signal obtained by subtraction by the subtraction unit, a calculation unit that calculates the signal strength of the detection signal received by the portable device-side reception unit, and a response signal including information on the signal strength calculated by the calculation unit A portable device-side transmitter for transmitting.

  In the in-vehicle communication system according to one aspect of the present application, the in-vehicle-side transmission unit includes a phase inverter that changes the phase of a signal to be transmitted by 180 degrees, a path that passes through the phase inverter, and the phase inverter. And a switch for switching a route not to be performed at a predetermined cycle.

  An in-vehicle device according to an aspect of the present application is an in-vehicle device that detects the position of the portable device by performing wireless communication with the portable device, and alternately detects two types of detection signals that are 180 degrees out of phase with each other. Based on the response signal received by the receiving unit, the receiving unit that receives the response signal transmitted from the portable device with respect to the detection signal transmitted by the transmitting unit, And a position detecting unit for detecting the position of.

  A portable device according to one aspect of the present application is a portable device that performs wireless communication with an in-vehicle device, and a reception unit that receives two types of detection signals that are alternately transmitted from the in-vehicle device and that are 180 degrees out of phase with each other; A subtractor for subtracting the other from one of the two types of detection signals received, a calculator for calculating the signal strength of the detection signal received by the receiver based on a signal obtained by subtraction by the subtractor; A transmission unit that transmits a response signal including information on the signal strength calculated by the calculation unit.

  In the above aspect, when the detection signal is transmitted from the in-vehicle device on the transmission side, two types of detection signals whose phases are different from each other by 180 degrees are transmitted, and the received portable device receives the two types of detection signals. Subtract one from the other. Therefore, environmental noise that does not have a specific phase relationship such as the same phase or opposite phase as the phase of the detection signal can be reduced on the portable device side, and the signal strength of the received detection signal is accurately measured. be able to. In addition, by returning a response signal including the signal strength measured on the portable device side to the in-vehicle device, the in-vehicle device can accurately detect the position of the portable device.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
FIG. 1 is a schematic diagram illustrating a schematic configuration of an in-vehicle control system according to the present embodiment. The in-vehicle control system according to the present embodiment includes, for example, an in-vehicle device 100 mounted on a vehicle C and a portable device 200 operated by an occupant.

  The in-vehicle device 100 is one of a plurality of ECUs (Electronic Controller Units) mounted on the vehicle, and includes, for example, control related to locking and unlocking of a vehicle door, an air conditioner, interior and exterior lamps, body This is a so-called BCM (Body Control Module) that performs integrated control related to the operation of the actuators of the system.

  The in-vehicle device 100 includes an RF reception antenna 105a and a plurality of LF transmission antennas 106a to 106e in order to perform wireless communication with the portable device 200. The RF receiving antenna 105a is an antenna built in the in-vehicle device 100, for example, and receives a signal having an RF band frequency (hereinafter also referred to as an RF signal). The LF transmission antennas 106a to 106e are antennas provided around each vehicle door provided in the vehicle C, for example, and transmit a signal having an LF band frequency (hereinafter also referred to as an LF signal). The LF transmission antennas 106a to 106e are provided, for example, around a driver's seat, a passenger seat, a right rear seat, a vehicle door for the left rear seat, and a rear door.

  The portable device 200 includes an unlock button 203a and a lock button 203b in order to accept operations related to unlocking and locking of the vehicle door. In addition, the portable device 200 includes an RF transmission unit 204 and an LF reception unit 205 in order to perform wireless communication with the in-vehicle device 100 mounted on the vehicle C (see FIG. 3). When the portable device 200 receives an operation related to unlocking or locking the vehicle door by the unlock button 203a or the lock button 203b, the portable device 200 transmits a signal instructing unlocking or locking of the vehicle door from the RF transmission unit 204. Is possible.

  Here, the communication range of the wireless communication using the LF signal is about 1 m, whereas the communication range of the wireless communication using the RF signal is about several tens of meters. Using this, it is possible to switch between unlocking all the doors provided in the vehicle C and unlocking a specific door (for example, a door on the driver's seat side) provided in the vehicle C. For example, when the portable device 200 exists in any one of the communication ranges Ra to Re by the LF transmission antennas 106 a to 106 e of the vehicle C, when the operation signal instructing the unlocking of the vehicle door is received from the portable device 200, The apparatus 100 may perform control to unlock all doors of the vehicle C. Further, when the portable device 200 does not exist in the communication ranges Ra to Re by the LF transmitting antennas 106a to 106e, when the operation signal instructing the unlocking of the vehicle door is received from the portable device 200, the in-vehicle device 100 has a specific Control to unlock the door may be performed.

  FIG. 2 is a block diagram illustrating the internal configuration of the in-vehicle device 100. The in-vehicle device 100 includes a control unit 101, a storage unit 102, an input / output unit 103, an in-vehicle communication unit 104, an RF reception unit 105, an LF transmission unit 106, and the like.

  The control unit 101 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU in the control unit 101 executes the control program stored in the ROM, thereby controlling the operation of the hardware included in the in-vehicle device 100 and causing the entire device to function as the in-vehicle device of the present application. The RAM in the control unit 101 stores various data generated during execution of the control program. Note that the control unit 101 may have functions such as a timer that measures an elapsed time from when a measurement start instruction is given to when a measurement end instruction is given, and a counter that counts the number.

  The storage unit 102 is configured by a nonvolatile memory such as an EEPROM (Electronically Erasable Programmable Read Only Memory), and stores various types of information. Here, the various types of information stored in the storage unit 102 include authentication information such as an ID (Identifier) of the vehicle C on which the in-vehicle device 100 is mounted, an ID of the portable device 200 that is a communication partner, and key information used for encryption processing, for example. Is included.

  The input / output unit 103 includes, for example, an interface for connecting the door lock mechanism 111 and the door lock operation unit 112.

  The door lock mechanism 111 includes a mechanical mechanism for locking or unlocking each vehicle door of the vehicle C, an actuator for electrically operating the mechanical mechanism, and the like. The door lock operation unit 112 is, for example, a key cylinder provided on a vehicle door for a driver's seat, a request switch provided on a door handle, or the like.

  For example, when a mechanical key (not shown) is used, the mechanical key is inserted into a key cylinder provided on the vehicle door, and a locking operation or an unlocking operation is performed. At this time, the door lock mechanism 111 operates an actuator or the like to lock or unlock the door. Information that the key cylinder is operated by the mechanical key is output to the door lock mechanism 111 through the input / output unit 103, and the door lock mechanism 111 is configured to operate based on the output information.

  Further, when an occupant having the portable device 200 operates a request switch provided on the door handle of the vehicle C, wireless communication is performed between the in-vehicle device 100 and the portable device 200. In the wireless communication, when the in-vehicle device 100 transmits a detection signal for detecting the portable device 200 from the LF transmission antennas 106a to 106e and receives a response signal for the detection signal from the valid portable device 200, the in-vehicle device 100 Lock or unlock the door. The request switch may be a push button type switch or a switch using a contact sensor that detects contact with the door handle.

  Further, the vehicle door may be locked and unlocked by wireless communication between the in-vehicle device 100 and the portable device 200 without the occupant operating the door lock operation unit 112. For example, when the operation signal transmitted from the portable device 200 is received by the RF receiving antenna 105a, the in-vehicle device 100 locks or unlocks the vehicle door based on the unlocking or locking information included in the received operation signal. You may lock.

  The in-vehicle communication unit 104 includes, for example, a CAN communication interface (CAN: Controller Area Network), and is connected to another ECU included in the vehicle C via a CAN bus. The in-vehicle communication unit 104 transmits / receives data to / from another ECU (not shown) according to the CAN protocol.

  The RF receiving unit 105 is connected to the RF receiving antenna 105a, receives a RF signal through the RF receiving antenna 105a, a measurement circuit that measures a received signal strength (RSSI) of the received signal, and the like. Is provided. In the present embodiment, the RF reception unit 105 receives an operation signal transmitted from the portable device 200 through the RF reception antenna 105 a and sends the received operation signal to the control unit 101.

  The LF transmission unit 106 includes a signal generation circuit that generates a signal to be transmitted based on a signal input from the control unit 101, an amplification circuit that amplifies the generated signal, and the like. The amplified signal is transmitted to the LF transmission antenna 106a. Transmit to outside from ~ 106e. The LF transmission unit 106 transmits, for example, a detection signal (LF signal) for detecting the portable device 200 through the LF transmission antennas 106 a to 106 e according to an instruction from the control unit 101. Here, it is assumed that the authentication information stored in the storage unit 102 is added to the LF signal transmitted from the LF transmission unit 106. As will be described later, in the present embodiment, the LF transmitter 106 alternately transmits detection signals whose phases are different from each other by 180 degrees.

  FIG. 3 is a block diagram illustrating the internal configuration of the portable device 200. The portable device 200 includes a control unit 201, a storage unit 202, an operation unit 203, an RF transmission unit 204, an LF reception unit 205, and the like.

  The control unit 201 includes, for example, a CPU and a ROM. The CPU in the control unit 201 executes the control program stored in the ROM, thereby controlling the operation of each hardware included in the portable device 200 and causing the entire device to function as the portable device of the present application. The control unit 201 may include functions such as a timer that measures an elapsed time from when a measurement start instruction is given to when a measurement end instruction is given, and a counter that counts the number.

  The storage unit 202 is configured by a nonvolatile memory such as an EEPROM, and stores various types of information. Here, the various types of information stored in the storage unit 202 include, for example, the ID of the portable device 200, the ID of the vehicle C on which the in-vehicle device 100 serving as a communication partner is mounted, key information used for encryption processing, and the like.

  The operation unit 203 includes an interface for accepting an operation by an occupant. In the present embodiment, the operation unit 203 includes an unlock button 203a that is operated when the door of the vehicle C is unlocked, and a lock button 203b that is operated when the door of the vehicle C is locked. When the unlock button 203a (or lock button 203b) is operated by the occupant, the operation unit 203 outputs a signal indicating that the unlock button 203a (or lock button 203b) has been operated to the control unit 201. When the control unit 201 receives a signal indicating that the unlock button 203a (or the lock button 203b) has been operated, the control unit 201 sends a control signal for instructing unlocking (or locking) the door of the vehicle C to the RF transmission unit 204. To do.

  The RF transmission unit 204 includes a signal generation circuit that generates an RF signal from the control signal output from the control unit 201, an amplification circuit that amplifies the generated signal, and the like. The amplified signal is externally transmitted from the RF transmission antenna 204a. Send to. For example, the RF transmission unit 204 can transmit an RF signal instructing unlocking (or locking) of the vehicle door from the RF transmission antenna 204a in accordance with a control signal from the control unit 201. Here, it is assumed that authentication information stored in the storage unit 202 is added to the RF signal transmitted from the RF transmission unit 204.

  The LF reception unit 205 is connected to the LF reception antenna 205a, and includes a reception circuit that receives an LF signal through the LF reception antenna 205a, a measurement circuit that measures the signal strength of the received signal, and the like. In the present embodiment, when the LF reception unit 205 receives the detection signal transmitted from the LF transmission antennas 106a to 106e of the vehicle C by the LF reception antenna 205a, the LF reception unit 205 subtracts the environmental noise included in the received signal. The detection signal after the subtraction of the environmental noise is sent to the control unit 201. When the control unit 201 receives a detection signal from the LF reception unit 205, the control unit 201 performs processing for transmitting a response signal to the detection signal from the RF transmission unit 204. At this time, the control unit 201 adds signal strength (RSSI) information of the detection signal to the response signal to be transmitted, and transmits the added RF signal from the RF transmission unit 204.

Hereinafter, operations of the in-vehicle device 100 and the portable device 200 according to the present embodiment will be described.
FIG. 4 is a block diagram illustrating a configuration example of the LF transmission unit 106 included in the in-vehicle device 100. The LF transmission unit 106 includes, for example, a signal generation circuit 1061, an amplification circuit 1062, a switch circuit 1063, and a phase inversion circuit 1064.

  The signal generation circuit 1061 generates a signal to be transmitted based on the signal input from the control unit 101. The signal generated by the signal generation circuit 1061 is input to the subsequent amplification circuit 1062, and the signal is amplified by the amplification circuit 1062.

  The switch circuit 1063 receives a switching signal having a constant period input from the control unit 101. The switch circuit 1063 alternately switches the output destination to a path that does not pass through the phase inversion circuit 1064 and an output destination that passes through the phase inversion circuit 1064 according to the input switching signal. When the switch circuit 1063 selects a path that does not pass through the phase inverter circuit 1064, the signal amplified by the amplifier circuit 1062 is output to each of the LF transmission antennas 106a to 106e without the phase being inverted. On the other hand, when the path through the phase inverter circuit 1064 is selected by the switch circuit 1063, the phase of the signal amplified by the amplifier circuit 1062 is inverted (the phase is changed by 180 degrees) by the phase inverter circuit 1064. The inverted signal is output to each of the LF transmission antennas 106a to 106e.

  FIG. 5 is an explanatory diagram for explaining LF signals transmitted and received by the in-vehicle device 100 and the portable device 200. FIG. 5A shows an example of an LF signal (transmission signal) transmitted from the in-vehicle device 100. As described above, the LF transmission unit 106 of the in-vehicle device 100 performs phase inversion at a predetermined cycle when transmitting the LF signal. In the example shown in FIG. 5A, the radio wave related to the LF signal transmitted from the LF transmitting antennas 106a to 106e has a phase that is 180 degrees different between the period A corresponding to one cycle and the period B following the period A. It shows how to hold it.

  FIG. 5B shows an example of an LF signal (received signal) received by the LF receiver 205 of the portable device 200. When environmental noise is generated around the vehicle C, the received signal received by the LF receiver 205 of the portable device 200 is more environmental noise than the LF signal transmitted from the LF transmitter 106 of the in-vehicle device 100. The signal is superimposed. In the example of FIG. 5B, for the sake of explanation, the LF signal (thick line) and the environmental noise (thin line) are shown separately.

  When the LF receiving unit 205 receives a signal, the control unit 201 of the portable device 200 performs a process of subtracting the signal corresponding to the period B from the signal corresponding to the period A. FIG. 5C shows an example of the LF signal after the subtraction process. When the environmental noise is not a signal having a specific phase relationship with the transmission target LF signal (for example, white noise), the environmental noise is not amplified by the subtraction processing executed by the control unit 201 and is converted into a relatively small value. Is done. Therefore, environmental noise can be reduced by the subtraction processing executed by the control unit 200.

  FIG. 6 is a flowchart for explaining a procedure of processing executed by the portable device 200. The control unit 201 of the portable device 200 determines whether or not the LF reception unit 205 has received the LF signal for the period A described above (step S101). If not received (S101: NO), the control unit 201 waits until an LF signal corresponding to the period A is received.

  When it is determined that the LF signal corresponding to the period A has been received (S101: YES), the control unit 201 stores the received LF signal in the storage unit 202 (step S102).

  Next, the control unit 201 determines whether or not the LF reception unit 205 has received the LF signal corresponding to the period B following the period A (that is, the LF signal whose phase has been inverted on the vehicle-mounted device 100 side) (step S1203). S103). If not received (S103: NO), the control unit 201 waits until an LF signal corresponding to the period B is received.

  When it is determined that the LF signal corresponding to the period B has been received (S103: YES), the control unit 201 determines the period B received in step S103 from the LF signal stored in the storage unit 202 in step S102. A subtraction process for subtracting the LF signal is executed (step S104).

  Next, the control unit 201 calculates the signal strength of the LF signal based on the signal after the subtraction process (step S105). At this time, the control unit 201 divides the amplitude value of the signal obtained by the subtraction process in step S104 by 2, and averages the signal strength of the LF signal corresponding to the period A and the signal strength of the LF signal corresponding to the period B. A value may be obtained.

  Next, the control unit 201 controls the RF transmission unit 204 to transmit an RF signal including the calculated signal strength information, and transmits the RF signal to the outside from the RF transmission unit 204 (step S106).

  The in-vehicle device 100 can acquire the signal strength of the LF signal measured by the portable device 200 by receiving the RF signal transmitted from the portable device 200 by the RF receiving unit 105. Since the signal strength is measured with the environmental noise reduced in the portable device 200, the in-vehicle device 100 detects the position of the portable device 200 based on the signal strength, thereby determining the position of the portable device 200. It is possible to detect with high accuracy, and it is possible to accurately determine whether the portable device 200 exists inside the vehicle or outside the vehicle.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 100 In-vehicle apparatus 101 Control part 102 Storage part 103 Input / output part 104 In-vehicle communication part 105 RF receiving part (on-vehicle side receiving part)
106 LF transmitter (on-vehicle transmitter)
111 Door Lock Mechanism 112 Door Lock Operation Unit 200 Portable Machine 201 Control Unit (Subtraction Unit, Calculation Unit)
202 Storage Unit 203 Operation Unit 203a Unlock Button 203b Lock Button 204 RF Transmitter (Portable Transmitter)
205 LF receiver (portable receiver)
1601 Signal generation circuit 1602 Amplifier circuit 1603 Switch circuit 1604 Signal inversion circuit

Claims (4)

An in-vehicle device mounted on a vehicle and a portable device capable of wireless communication with the in-vehicle device, and performing the wireless communication between the in-vehicle device and the portable device, the portable device An in-vehicle communication system for detecting the position of a machine,
The in-vehicle device is
An in-vehicle transmission unit that alternately transmits two types of detection signals that are 180 degrees out of phase with each other;
An in-vehicle side receiving unit that receives a response signal transmitted from the portable device in response to the detection signal transmitted by the in-vehicle side transmitting unit;
A position detection unit that detects the position of the portable device based on the response signal received by the in-vehicle side reception unit;
The portable device is
A portable device-side receiver that receives two types of detection signals transmitted from the in-vehicle-side transmitter;
A subtractor for subtracting the other from one of the two types of received detection signals;
Based on the signal obtained by subtraction by the subtracting unit, a calculating unit that calculates the signal strength of the detection signal received by the portable device-side receiving unit;
An in-vehicle communication system comprising: a portable device-side transmitter that transmits a response signal including information on the signal strength calculated by the calculator. The in-vehicle side transmitter is
A phase inverter that changes the phase of the signal to be transmitted by 180 degrees;
The in-vehicle communication system according to claim 1, further comprising: a switch that switches a path that passes through the phase inverter and a path that does not pass through the phase inverter at a predetermined period. An in-vehicle device that detects the position of the portable device by performing wireless communication with the portable device,
A transmission unit that alternately transmits two types of detection signals whose phases are different from each other by 180 degrees;
A receiving unit that receives a response signal transmitted from the portable device in response to the detection signal transmitted by the transmitting unit;
A vehicle-mounted apparatus comprising: a position detection unit that detects a position of the portable device based on a response signal received by the reception unit. A portable device that performs wireless communication with an in-vehicle device,
A reception unit that receives two types of detection signals that are alternately transmitted from the in-vehicle device and that are 180 degrees out of phase with each other;
A subtractor for subtracting the other from one of the two types of received detection signals;
A calculation unit that calculates a signal strength of the detection signal received by the reception unit based on a signal obtained by subtraction by the subtraction unit;
A portable device comprising: a transmission unit that transmits a response signal including information on the signal strength calculated by the calculation unit.

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