JP2014227647A - Electronic key system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic key system capable of detecting presence of a repeater.SOLUTION: After key authentication by bidirectional communication using radio waves of an LF band and radio waves of an UHF band, UWB communication using impulse signals of 3.1 GHz-10.25 GHz is performed. The impulse signals are defined as extremely short pulse signals whose pulse width is 2 ns or narrower and bandwidth is 500 MHz or wider. In a case of measuring a distance utilizing the impulse signals, when a speed of electromagnetic waves is defined as C and a bandwidth is defined as B, a distance resolution ▵r is represented by ▵r=C/2B. When 500 MHz is selected as the bandwidth, the distance resolution of about 0.3 m is obtained.

Description

  The present invention relates to an electronic key system that analyzes a response of an electronic key to a radio wave transmitted from a controlled object and allows the controlled object to operate.

  Patent Document 1 discloses a technique for detecting an illegal act using a repeater and prohibiting an operation of a controlled object due to the act in an electronic key system. In this technology, when an LF band radio wave is transmitted from a vehicle and the electronic key receives the radio wave, a UHF band radio wave including information indicating the reception intensity of the radio wave is transmitted from the electronic key. The vehicle control device measures the delay time from when the LF band radio wave is transmitted to when the UHF band radio wave is received, and there is a contradiction between the delay time and the information included in the UHF band radio wave. When this happens, door unlocking and engine starting are prohibited.

JP 2012-175518 A

  If the intensity information of the LF radio wave is relayed, matching with the delay time can be achieved, so that an illegal act is possible. In addition, when the delay time from the transmission of the LF radio wave to the reception of the UHF radio wave is longer than the modulation / demodulation delay time by the repeater, the repeater Cannot detect the presence of.

  The present invention has been made paying attention to such a problem, and an object thereof is to provide an electronic key system capable of detecting the presence of a repeater.

  An electronic key system that solves the above problem is an electronic key system that analyzes the response of an electronic key to a radio wave transmitted from a controlled object and permits the operation of the controlled object. When the repeater is present, the processing by the repeater is performed on the assumption that the propagation time from the transmission of the radio wave to the reception of the response is defined by the radio wave and the response processing time by the repeater. Distance measurement that measures the distance from the control object to the electronic key by detecting the impulse propagation time from the transmission of the impulse to the reception of the response to the impulse using the bandwidth capable of detecting the distance resolution capable of detecting the time On the condition that the distance measured by the means and the distance measuring means is equal to or less than a threshold value. That a control means is set to its gist.

  According to this configuration, the distance resolution can be increased by using an impulse with a wide bandwidth, so that the distance to the electronic key can be accurately measured. Thereby, when the distance to the electronic key exceeds the threshold, it can be detected that the repeater is interposed. Therefore, the presence of the repeater can be detected.

  With respect to the electronic key system, the operation control means determines the validity of the transmission source of the response while decrypting the response to the impulse using an encryption key, on the condition that the validity is affirmed. It is good also as validating the measurement result by a distance measurement means.

  According to this configuration, even if the repeater is used as a simulation of an electronic key, the repeater cannot follow the encrypted communication. Therefore, the control is performed regardless of whether the distance to the repeater is equal to or less than the threshold value. Subject operation is not allowed. Thereby, the fraudulent act using a repeater can be prevented.

  In the electronic key system, the operation control means may transmit the impulse only when allowing at least one of unlocking the vehicle door and starting the engine.

According to this configuration, since the opportunity for impulse communication is limited, current consumption can be reduced for both the vehicle and the electronic key.
In the electronic key system, the operation control means may transmit the impulse only in an area where the electronic key exists.

  According to this configuration, since the area where the impulse is transmitted is limited, the dark current to be controlled can be reduced.

  According to the present invention, the presence of a repeater can be detected.

The block diagram which shows the structure of an electronic key system. The top view which shows a mode that the interrogation signal by the electromagnetic wave of LF band is transmitted out of the vehicle interior. The top view which shows a mode that the electronic key has approached into the transmission area of the LF radio wave by the LF transmitter installed in the door of the driver's seat. The top view which shows a mode that the impulse signal is transmitted from the UWB transmitter installed around the driver's seat.

Hereinafter, an embodiment of an electronic key system will be described.
As shown in FIG. 1, the electronic key system 1 includes an electronic key 2 possessed by a vehicle owner and a security device 3 mounted on the vehicle. The electronic key system 1 can perform two types of two-way communication wirelessly between the electronic key 2 and the security device 3. On the other hand, bidirectional communication is defined as communication using LF band radio waves and UHF band radio waves. The other bidirectional communication is defined as UWB (Ultra Wide Band) communication using an impulse of 3.1 GHz to 10.25 GHz.

The electronic key 2 includes an LF reception circuit 21, a UHF transmission circuit 22, a UWB reception circuit 23, a UWB transmission circuit 24, and a microcomputer 25.
The LF receiving circuit 21 can receive the request signal transmitted from the security device 3. The request signal is defined as an LF band radio wave. When receiving the request signal, the LF reception circuit 21 generates a reception signal while performing electrical processing such as demodulating the signal and outputs the reception signal to the microcomputer 25.

  The microcomputer 25 includes a nonvolatile memory 25a. An ID unique to the electronic key 2 is stored in the memory 25a. When the reception signal is input from the LF reception circuit 21, the microcomputer 25 generates an original signal including the ID in order to respond to the request signal, and outputs the original signal to the UHF transmission circuit 22.

  The UHF transmission circuit 22 generates a response signal while electrically processing it, such as modulating the original signal input from the microcomputer 25, and transmits this response signal. A response signal to the request signal is defined as a radio wave in the UHF band.

  The UWB receiving circuit 23 can receive the impulse signal transmitted from the security device 3. The impulse signal is defined as a very short pulse signal having a pulse width of 2 ns or less and a bandwidth of 500 MHz or more. When measuring the distance using this impulse signal, if the speed of the electromagnetic wave is C and the bandwidth is B, the distance resolution Δr is expressed by Δr = C / 2B, and the bandwidth is 500 MHz. When selected, a distance resolution of about 0.3 m is obtained. When a repeater is interposed between the vehicle and the electronic key 2, it is assumed that the propagation time from the transmission of the radio wave to the reception of the response to the radio wave is defined by the radio wave and response processing time by the repeater. To do. In this example, an impulse signal is used that uses a bandwidth that provides a distance resolution capable of detecting the processing time by the repeater. When receiving the impulse signal, the UWB reception circuit 23 generates a reception signal while performing electrical processing such as demodulating the signal, and outputs the reception signal to the microcomputer 25.

  When the reception signal is input from the UWB reception circuit 23, the microcomputer 25 encrypts specific data included in the signal using an encryption key, and generates an original signal including the encrypted data. This original signal is output to the UWB transmission circuit 24.

The UWB transmission circuit 24 generates a response signal while performing electrical processing, such as modulating the original signal input from the microcomputer 25, and transmits this response signal by UWB communication.
The security device 3 includes an LF transmitter 31, a UHF receiver 32, a UWB transmitter 33, a UWB receiver 34, and a verification ECU (Electronic Control Unit) 35.

  The LF transmitter 31 generates a request signal while performing electrical processing such as modulating the original signal input from the verification ECU 35, and transmits the request signal to the periphery of the vehicle. The LF transmitter 31 is defined for both transmitting a request signal into the vehicle interior and transmitting a request signal outside the vehicle interior, and the latter is defined for each door.

  The UHF receiver 32 can receive a response signal to the request signal. When the UHF receiver 32 receives the response signal, the UHF receiver 32 generates a reception signal while performing electrical processing such as demodulating the signal, and outputs the reception signal to the verification ECU 35.

  The verification ECU 35 includes a non-volatile memory 35a. In the memory 35a, the ID of the regular electronic key 2 that matches the host vehicle is registered as a reference ID. When the reception signal is input from the UHF receiver 32, the verification ECU 35 compares the ID included in the reception signal with the reference ID. When the ID matches, the verification ECU 35 outputs an original signal including specific data to the UWB transmitter 33.

  The UWB transmitter 33 generates an impulse signal while performing electrical processing such as modulating the original signal input from the verification ECU 35, and transmits the impulse signal to the periphery of the vehicle. A total of two UWB transmitters 33 are installed around the driver's seat and the passenger seat. The impulse signal from each transmitter 33 is effective not only in the passenger compartment but also outside the passenger compartment through the corresponding door glass. For example, the impulse signal from the UWB transmitter 33 installed around the driver's seat is effective not only in the entire vehicle interior but also outside the passenger compartment through the door glass of the driver's seat and the door glass of the rear seat on the driver's seat. Reach.

  The UWB receiver 34 can receive a response signal for the impulse signal. When the UWB receiver 34 receives the response signal, the UWB receiver 34 generates a reception signal while performing electrical processing such as demodulating the signal, and outputs the reception signal to the verification ECU 35.

  When the received signal is input from the UWB receiver 34, the verification ECU 35 performs verification with the specific data while decrypting the encrypted data included in the received signal using the encryption key. The verification ECU 35 makes an affirmative determination that the transmission source of the response signal to the impulse signal is the regular electronic key 2 when the data matches.

  By the way, the verification ECU 35 detects the impulse propagation time from the transmission of the impulse signal to the reception of the response signal with respect to the impulse signal, and measures the distance from the vehicle to the electronic key 2. Therefore, the verification ECU 35 corresponds to a distance measuring unit. The verification ECU 35 validates the distance measurement result on the condition that the transmission source of the response signal to the impulse signal is affirmatively determined to be the regular electronic key 2. The verification ECU 35 permits both unlocking of the door lock and starting of the engine in the vehicle operation on the condition that the distance obtained by detecting the impulse propagation time is equal to or less than the threshold value. Therefore, the verification ECU 35 corresponds to an operation control unit.

Next, the operation of the electronic key system 1 will be described.
As shown in FIG. 2, on the assumption that all door locks are locked, the LF transmitter 31 of each door transmits a call signal using radio waves in the LF band all at once. For convenience, the transmission area of the interrogation signal by the LF transmitter 31 installed at the door of the driver's seat is defined as the transmission area 31a, and the transmission area of the interrogation signal by the LF transmitter 31 installed at the door of the passenger seat is the transmission area. It is defined as 31b. Further, the transmission area of the interrogation signal by the LF transmitter 31 installed on the door of the rear seat on the driver's seat side is defined as a transmission area 31c, and by the LF transmitter 31 installed on the door of the rear seat on the passenger seat side. The transmission area of the interrogation signal is defined as a transmission area 31d.

  As shown in FIG. 3, when the electronic key 2 enters any of the transmission areas 31a to 31d, a response signal to the call signal is transmitted from the electronic key 2. When this response signal is acquired by the verification ECU 35 via the UHF receiver 32, the entry of the electronic key 2 into any of the transmission areas 31a to 31d is detected. The verification ECU 35 selects the LF transmitters 31 installed in each door one by one in a predetermined order, and transmits a request signal from the LF transmitter 31. When the electronic key 2 is present in the transmission area 31a, a response signal to the request signal from the LF transmitter 31 installed at the door of the driver's seat is acquired by the verification ECU 35. Thereby, the approach of the electronic key 2 to the transmission area 31a is detected. The verification ECU 35 corresponds to a specifying unit that specifies an area where the electronic key 2 exists.

  As shown in FIG. 4, based on the above assumption, only the UWB transmitter 33 closer to the transmission area 31a out of the two UWB transmitters 33, that is, the UWB transmitter 33 installed around the driver's seat only. An impulse signal is transmitted. When this impulse signal is received by the electronic key 2, a response signal for the impulse signal is transmitted from the electronic key 2, and this response signal is acquired by the verification ECU 35. The verification ECU 35 detects the impulse propagation time from the transmission of the impulse signal to the reception of the response signal to the impulse signal, and measures the distance from the vehicle to the electronic key 2. The verification ECU 35 allows the door lock to be unlocked if the distance obtained by the measurement is equal to or less than a threshold value, for example, within 3 meters. Usually, since the transmission area 31a is defined as a range of about 0.7 to 1.0 meters from the door of the driver's seat, the door lock can be unlocked when the electronic key 2 is in the transmission area 31a. become.

  After the driver's seat door is opened, a request signal is transmitted to the passenger compartment when the door is closed. When a response signal to the request signal is acquired by the verification ECU 35, the entry of the electronic key 2 into the vehicle compartment is detected. The verification ECU 35 selects a UWB transmitter 33 installed around the driver's seat and transmits an impulse signal only from this UWB transmitter 33. When this impulse signal is received by the electronic key 2, a response signal for the impulse signal is transmitted from the electronic key 2, and this response signal is acquired by the verification ECU 35. The verification ECU 35 detects the impulse propagation time from the transmission of the impulse signal to the reception of the response signal to the impulse signal, and measures the distance from the vehicle to the electronic key 2. The verification ECU 35 allows the engine to start if the distance obtained by the measurement is equal to or less than a threshold value, for example, within 3 meters. When the electronic key 2 is in the passenger compartment, the engine is allowed to start. For the two threshold values, the former and the latter may adopt the same configuration, or different configurations, that is, the former is set to the first threshold (for example, 3 meters) while the latter is set to the second threshold (for example, 2 meters). ) May be adopted.

  When a door lock switch provided on the outside handle of the driver's seat door is operated, a request signal is transmitted to the transmission area 31a. When a response signal to the request signal is acquired by the verification ECU 35, the entry of the electronic key 2 into the transmission area 31a is detected. In this case, the door lock is locked without going through UWB communication using an impulse signal. The verification ECU 35 corresponds to an identification means for identifying the control content that is an allowable purpose.

As described above, according to the present embodiment, the following effects can be obtained.
(1) Since the distance resolution is enhanced by using an impulse signal having a wide bandwidth, the distance to the electronic key 2 can be accurately measured. Thereby, when the distance to the electronic key 2 exceeds the threshold value, it can be detected that the repeater is interposed. Therefore, the presence of the repeater can be detected.

  (2) The verification ECU 35 determines the validity of the transmission source of the response signal while decrypting the response signal to the impulse signal using the encryption key, and the distance measurement result on the condition that the validity is affirmed. Activate. As a result, even if the repeater is used as a simulation of the electronic key 2, the repeater cannot follow the encrypted communication. Therefore, whether the distance to the repeater is less than the threshold or not, the vehicle operation is Not allowed. Thereby, the fraudulent act using a repeater can be prevented.

  (3) The verification ECU 35 performs UWB communication using an impulse signal when allowing the door lock to be unlocked or starting the engine, but does not perform UWB communication when the door lock is locked. Thereby, since the opportunity for impulse communication to be performed is limited, current consumption can be reduced for both the vehicle and the electronic key 2. Moreover, responsiveness can be improved about locking of a door lock.

  (4) The verification ECU 35 transmits an impulse signal only in the area where the electronic key 2 exists. Thereby, since the area where the impulse signal is transmitted is limited, the dark current of the vehicle can be reduced.

In addition, the said embodiment can also be changed and actualized as follows.
・ UWB communication is regulated by law to have a bandwidth of 500 MHz or more. In the above embodiment, 500 MHz is adopted, but if a larger bandwidth is adopted, the distance resolution can be further improved.

-The installation location and the number of the LF transmitter 31 and the UWB transmitter 33 are not limited to the aspect of the above embodiment.
The UHF communication according to the above embodiment may be substituted with UWB communication.

-The controlled object is not limited to vehicles. When opening or closing a door or shutter of a building, two types of two-way communication may be applied following the above embodiment.
Next, a technical idea that can be grasped from the above embodiment and another example will be described.

(A) In the electronic key system, an identification means for identifying a control content that is an allowable purpose is provided.
(B) The electronic key system includes a specifying means for specifying an area where the electronic key exists.

  DESCRIPTION OF SYMBOLS 1 ... Electronic key system, 2 ... Electronic key, 3 ... Security apparatus, 21 ... LF reception circuit, 22 ... UHF transmission circuit, 23 ... UWB reception circuit, 24 ... UWB transmission circuit, 25 ... Microcomputer, 25a ... Memory, 31 ... LF transmitter, 31a to 31d ... transmission area, 32 ... UHF receiver, 33 ... UWB transmitter, 34 ... UWB receiver, 35 ... verification ECU (distance measurement means, operation control means, identification means, identification means), 35a …memory.

Claims (4)

In an electronic key system that analyzes the response of the electronic key to radio waves transmitted from the controlled object and allows the controlled object to operate,
When a repeater is interposed between the control object and the electronic key, the propagation time from the transmission of the radio wave to the reception of the response is defined by the radio wave and the response processing time by the repeater. Assuming that
By detecting the impulse propagation time from the transmission of the impulse using the bandwidth that can obtain the distance resolution capable of detecting the processing time by the repeater to the reception of the response to the impulse, from the control object to the electronic key A distance measuring means for measuring the distance;
An electronic key system comprising: an operation control unit that allows the operation of the control target on condition that the distance measured by the distance measuring unit is equal to or less than a threshold value. The operation control means determines the validity of the transmission source of the response while decrypting the response to the impulse using an encryption key, and the measurement result by the distance measuring means on the condition that the validity is affirmed. The electronic key system according to claim 1, wherein the electronic key system is activated. The electronic key system according to claim 1 or 2, wherein the operation control means transmits the impulse only when at least one of unlocking the vehicle door and starting the engine is permitted. The electronic key system according to any one of claims 1 to 3, wherein the operation control means transmits the impulse only in an area where the electronic key exists.