JP2012144905A - Electronic key system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic key system capable of more accurately determining whether or not communication through a relay is unauthorized.SOLUTION: An on-vehicle device 20 sends measuring signals Srs1 and Srs2 having different signal intensities. When a difference in RSSI of the signals is equal to or lower than a threshold, a communication using a relay is determined to be unauthorized. Both of the measuring signals Srs1 and Srs2 are sent within a prescribed period of time. The prescribed period of time is set small in extent so that the difference in the RSSI of the both measuring signals Srs1 and Srs2 associated with a move of an electronic key 10 is equal to or lower than the threshold even when the both measuring signals Srs1 and Srs2 are sent through the relay with the identical signal intensity. Thus, even when the electronic key 10 is moved, a determination of an unauthorized communication through the relay is accurately made.

Description

  The present invention relates to an electronic key system.

  In the conventional electronic key system, locking / unlocking of the vehicle door, engine starting, and the like are permitted through wireless communication between the electronic key and the vehicle. For example, the vehicle includes an in-vehicle antenna that transmits a request signal to an in-vehicle communication area and an out-of-vehicle antenna that transmits a request signal to an out-of-vehicle communication area around the vehicle. When the electronic key that has entered any communication area receives the request signal, the electronic key transmits a response signal including an ID code. The vehicle permits locking / unlocking of the vehicle door when collation of the ID code included in the response signal from the electronic key existing in the outside communication area is established. On the other hand, the vehicle permits the start of the engine when the verification of the ID code included in the response signal from the electronic key existing in the in-vehicle communication area is established.

  In recent years, there is a concern about unauthorized communication in which an electronic key that exists far away using a repeater that relays radio waves (request signal, response signal) is disguised as if it exists outside the vehicle interior. Unauthorized communication using this repeater may cause unlocking of the vehicle door or engine start. Therefore, for example, as disclosed in Patent Document 1, a security measure against unauthorized communication using a repeater is considered.

JP 2006-118886 A

  The present applicant is considering preventing unauthorized communication using a repeater by changing the signal strength of a radio signal transmitted and received between the vehicle and the electronic key. For example, the vehicle sequentially transmits a plurality of radio signals having different signal strengths. The electronic key detects the signal strength of a plurality of radio signals from the vehicle. Here, the repeater does not imitate the signal strength of the radio signal. That is, even if the repeater receives a plurality of wireless signals having different signal strengths from the vehicle, the relay device transmits the wireless signals to the electronic key with the same signal strength. Therefore, when a repeater exists between the vehicle and the electronic key, the electronic key receives a radio signal having the same signal strength. At this time, it is determined that the communication is unauthorized using the repeater, and the unlocking of the vehicle door is not permitted.

  In the above configuration, if the electronic key moves after receiving a radio signal and before receiving the next radio signal, each radio signal received by the electronic key is received despite the presence of a repeater. The signal strength may not be the same. As a result, there is a risk that it may be determined that the communication is not unauthorized using the repeater even though the repeater is used.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electronic key system capable of more accurately determining whether or not the communication is unauthorized using a repeater.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
According to the first aspect of the present invention, in the electronic key system in which control of the control target is executed through a wireless signal transmitted and received between the control target and the electronic key, the control target or the electronic key is a signal within a certain time. A detection unit configured to transmit a plurality of radio signals having different intensities and detect a signal intensity of each of the radio signals transmitted from the control target or the electronic key provided in the electronic key or the control target; When the difference in signal strength of each wireless signal that is provided on the target or the electronic key and is recognized through the detection unit exceeds a threshold set based on the difference in signal strength between the transmitted wireless signals It is determined that the communication is not unauthorized using a repeater, and the execution of the control of the control target is permitted, and if it is equal to or less than the threshold, it is determined that the communication is unauthorized using the repeater. A determination unit that prohibits execution of control of the object to be controlled, and the electronic key is moved within the predetermined time even when the signal strength of each wireless signal is the same through the repeater during the predetermined time. The gist of the invention is that the difference in signal strength of each radio signal from the repeater is set to be equal to or less than a threshold value.

  According to the configuration, a plurality of radio signals having different signal strengths are transmitted. When the difference in signal strength between these signals is less than or equal to the threshold value, it is determined that the communication is illegal using the repeater. This is because the repeater does not imitate the signal strength of the radio signal, and therefore, when the repeater is used, the difference in signal strength of each radio signal transmitted from the repeater approximates zero. However, even when a repeater is used, a difference occurs in the signal strength of each radio signal detected through the detection unit when the electronic key carried by the user moves. In this regard, in the above configuration, each radio signal is transmitted within a certain time. The shorter the fixed time is set, the smaller the distance that the electronic key can move during that time, so the difference in signal strength of each radio signal accompanying the movement of the electronic key becomes smaller. From such a viewpoint, even when each wireless signal having the same signal strength is transmitted from the repeater for a certain period of time, the difference in signal strength between the wireless signals accompanying the movement of the electronic key is less than or equal to the threshold value. It is set to a certain time. Thereby, even when the electronic key is moved, it is correctly determined that the communication is illegal using the repeater.

  According to a second aspect of the present invention, there is provided the electronic key system according to the first aspect, wherein the predetermined time includes a difference in signal arrival distance corresponding to a signal strength of each of the radio signals, and an assumed maximum moving speed of the user. Its gist is that it is calculated by dividing by.

  According to this configuration, it is possible to prevent the electronic key from moving beyond the difference in signal arrival distance of each radio signal within a certain time. As a result, when each wireless signal is transmitted from the repeater with the same signal strength, the difference in signal strength of each wireless signal exceeds the threshold with the movement of the electronic key, and thus the repeater is used. It is possible to suppress erroneous determination that the communication is not unauthorized.

  According to a third aspect of the present invention, in the electronic key system according to the first or second aspect, the detection unit is provided in the electronic key and is a plurality of measurement signals that are the plurality of radio signals from the control target. The signal strength of the signal is detected, and the electronic key includes the signal strength information signal recognized through the detection unit and transmits the signal strength information signal, and the determination unit is provided in the control target. In addition, the gist is to determine whether or not the communication is unauthorized using a repeater based on the signal strength of each measurement signal included in the signal strength information signal.

  According to this configuration, the detection result of the detection unit is transmitted to the control target through the signal strength information signal. Accordingly, it is possible to determine whether or not the communication is unauthorized using the repeater through the determination unit in the control target. As described above, by providing the determination unit in the control target, an electronic key that requires higher portability than the control target can be configured more compactly.

  According to the present invention, in the electronic key system, it is more accurately determined whether or not the communication is an unauthorized communication using a repeater.

The block diagram of an electronic key system. The timing chart which shows RSSI and transmission timing of various signals. The top view of the vehicle which showed transmission areas, such as a signal for measurement. The elements on larger scale of FIG. The flowchart which shows the process sequence of the electronic key control part 11 and the vehicle-mounted control part 21. FIG.

Hereinafter, an electronic key system according to the present invention will be described with reference to FIGS.
As shown in FIG. 1, the electronic key system 1 includes an electronic key 10 possessed by a user and an in-vehicle device 20. Mutual communication is performed between the electronic key 10 and the in-vehicle device 20, and locking / unlocking of the vehicle door and starting of the engine are permitted on the condition that the mutual communication is established outside and inside the vehicle.

<Electronic key>
The electronic key 10 includes an electronic key control unit 11, an LF reception unit 12, and a UHF transmission unit 13.

  The electronic key control unit 11 is configured by a computer unit and includes a nonvolatile memory 11a. An ID code unique to the electronic key 10 is stored in the memory 11a.

  As shown in FIG. 2, the LF receiver 12 includes a wake signal Swk and a first measurement signal Srs1, which are transmitted from the in-vehicle device 20 through the reception antenna 12a, and a wake signal Swk and a second measurement signal Srs2. Are continuously received. Then, the LF receiver 12 demodulates these signals into pulse signals and outputs them to the electronic key controller 11. The wake signal Swk and the measurement signals Srs1 and Srs2 are LF (Low Frequency) band radio signals.

  Further, as shown in FIG. 1, the LF receiver 12 is provided with an RSSI detection circuit 16. The RSSI detection circuit 16 detects received signal strength RSSI (Receive Signal Strength Indication) of both measurement signals Srs1 and Srs2, and outputs the detection result to the electronic key control unit 11.

  When recognizing the wake signal Swk, the electronic key control unit 11 recognizes the RSSI of each of the measurement signals Srs1 and Srs2 input thereafter through the RSSI detection circuit 16. When the electronic key control unit 11 recognizes the second wake signal Swk and the second measurement signal Srs2, the electronic key control unit 11 generates an ack signal Sac and outputs it to the UHF transmission unit 13. The UHF transmission unit 13 modulates the ACK signal Sac and transmits it as a UHF (Ultra High Frequency) band radio signal via its own transmission antenna 13a.

As shown in FIG. 2, a challenge signal Scc is transmitted from the in-vehicle device 20 in response to the ACK signal Sac.
When the LF receiving unit 12 receives the challenge signal Scc via the receiving antenna 12a, the LF receiving unit 12 demodulates the challenge signal Scc into a pulse signal and outputs it to the electronic key control unit 11. When the challenge signal Scc is input from the LF receiving unit 12, the electronic key control unit 11 recognizes the challenge code included in the challenge signal Scc. Then, the electronic key control unit 11 generates a response code by encrypting the challenge code.

The electronic key control unit 11 generates a response signal Sre including the generated response code and RSSI of both measurement signals Srs1 and Srs2 as RSSI information, and outputs this signal to the UHF transmission unit 13. The UHF transmission unit 13 modulates the response signal Sre and transmits the response signal Sre as a UHF band radio signal via the transmission antenna 13a.
<In-vehicle device>
As shown in FIG. 1, the in-vehicle device 20 includes an in-vehicle control unit 21, an in-vehicle transmission unit 22, an in-vehicle transmission unit 23, and an in-vehicle reception unit 24. In addition, a lock switch 36, an engine switch 33, a door lock device 34, and an engine device 35 are electrically connected to the in-vehicle control unit 21.

  As shown in an enlarged view in the circle of FIG. 3, the outside transmission unit 22 is built in the outside door handle 4 of the vehicle door. The lock switch 36 is provided on the outside door handle 4 and outputs an operation signal to that effect to the in-vehicle control unit 21 when pressed by the user.

  The in-vehicle receiving unit 24 is provided substantially in the center of the vehicle interior. Further, two in-vehicle transmission units 23 are provided along the vertical direction in FIG. Furthermore, the engine switch 33 is provided in the vicinity of the driver's seat, and outputs an operation signal to that effect to the in-vehicle control unit 21 when pressed by the user. Further, the door lock device 34 automatically locks and unlocks the vehicle door when the vehicle door is closed.

  The in-vehicle control unit 21 is configured by a computer unit and includes a nonvolatile memory 21a. In the memory 21a, the same ID code as the ID code stored in the electronic key 10 is stored.

  When the in-vehicle control unit 21 recognizes that the lock switch 36 has been operated, the in-vehicle control unit 21 sequentially generates the wake signal Swk, the first measurement signal Srs1, the wake signal Swk, and the second measurement signal Srs2, and generates them. Output to the transmitter 22.

  When the wake signal Swk and the first measurement signal Srs1, and the wake signal Swk and the second measurement signal Srs2 are continuously input from the in-vehicle control unit 21, the outside-vehicle transmission unit 22 modulates them sequentially. Then, the outside transmission unit 22 transmits the modulated signals as LF band radio signals via its transmission antenna 22a.

  As shown in FIG. 2, the signal strength of the first measurement signal Srs1 is set to be stronger than the signal strength of the second measurement signal Srs2. Therefore, the areas where the first measurement signal Srs1 and the second measurement signal Srs2 are transmitted are different. Specifically, as shown in FIG. 3, the first measurement signal Srs1 is transmitted to a first transmission area 31 formed in a semicircular shape outside each outside door. The first transmission area 31 is formed with a radius R1 with the outside door handle 4 as the center. The second measurement signal Srs2 is transmitted to the second transmission area 32 formed in a semicircular shape with a radius R2 smaller than the radius R1. That is, the second transmission area 32 is formed in a form included in the first transmission area 31. In the present embodiment, the difference between the radius R2 and the radius R1 is set to 40 cm. In other words, the signal intensities of both measurement signals Srs1, Srs2 are set so that the difference between the radius R2 and the radius R1 is 40 cm.

  Further, as shown in FIG. 2, both measurement signals Srs1, Srs2 are transmitted within a predetermined time T1. In this embodiment, this fixed time T1 is set to 300 ms. A method for calculating the fixed time T1 will be described in detail later.

As shown in FIG. 2, the ACK signal Sac is returned from the electronic key 10 that has received the second wake signal Swk and the second measurement signal Srs2.
The in-vehicle receiving unit 24 receives the ACK signal Sac through the receiving antenna 24a. Then, the in-vehicle receiving unit 24 demodulates the ACK signal Sac into a pulse signal and outputs it to the in-vehicle control unit 21.

  When the in-vehicle control unit 21 recognizes the ACK signal Sac, the in-vehicle control unit 21 generates a challenge signal Scc including a challenge code and outputs it to the outside transmission unit 22. At this time, the in-vehicle control unit 21 generates a response code by encrypting the challenge code. The encryption key used for this encryption is the same for the electronic key 10 and the in-vehicle device 20. When the challenge signal Scc is input from the in-vehicle control unit 21, the vehicle outside transmission unit 22 modulates the challenge signal Scc and transmits the modulated signal via its own transmission antenna 22a.

As shown in FIG. 2, a response signal Sre is returned from the electronic key 10 in response to the challenge signal Scc.
The in-vehicle receiving unit 24 receives the response signal Sre from the electronic key 10 via the receiving antenna 24a. Then, the in-vehicle receiver 24 demodulates the response signal Sre into a pulse signal and outputs it to the in-vehicle controller 21.

  The in-vehicle control unit 21 recognizes the ID code included in the response signal Sre, the response code, and the RSSI of both measurement signals Srs1 and Srs2, which are RSSI information. The vehicle-mounted control unit 21 collates the response code generated by itself with the response code included in the response signal Sre (response collation). Moreover, the vehicle-mounted control part 21 collates with the ID code contained in the response signal Sre, and the ID code memorize | stored in the memory 21a (ID code collation). When it is determined that the response verification and ID code verification have been established, the in-vehicle control unit 21 determines whether or not the communication is an unauthorized communication using a repeater.

  Specifically, when the difference between the RSSI of the first measurement signal Srs1 recognized based on the RSSI information and the RSSI of the second measurement signal Srs2 exceeds the threshold value, the in-vehicle control unit 21 determines whether the electronic key 10 It is determined that the communication with is not illegal using a repeater. Further, when the difference between the recognized RSSI of the first measurement signal Srs1 and the RSSI of the second measurement signal Srs2 is equal to or smaller than the threshold value, the in-vehicle control unit 21 relays communication with the electronic key 10. Judge that it is an unauthorized one using a container. This threshold value is set based on the RSSI difference between the measurement signals Srs1 and Srs2 transmitted from the in-vehicle device 20.

  The on-vehicle controller 21 switches the lock / unlock state of the vehicle door through the door lock device 34 when determining that the communication is not unauthorized using the repeater. On the other hand, when the vehicle-mounted control unit 21 determines that the communication is unauthorized using the repeater, the vehicle-mounted control unit 21 does not switch the lock / unlock state of the vehicle door.

  In addition, when the in-vehicle control unit 21 recognizes that the engine switch 33 has been operated, the wake signal Swk and the first signal are transmitted via the in-vehicle transmission unit 23 and the transmission antenna 23a in the same manner as when the lock switch 36 is operated. The measurement signal Srs1, the wake signal Swk, and the second measurement signal Srs2 are continuously transmitted to the vehicle interior. The signal intensity and transmission timing of these signals are the same as those of the signals transmitted via the above-described outside transmission unit 22. When it is determined that response verification and ID code verification have been established, the in-vehicle control unit 21 determines whether or not the communication is an unauthorized communication using a repeater. And when the vehicle-mounted control part 21 judges that it is not the unauthorized communication which uses a repeater, it starts an engine through the engine apparatus 35. FIG. On the other hand, the in-vehicle control unit 21 does not start the engine when it is determined that the communication is unauthorized using the repeater.

Next, unauthorized communication using a repeater and processing operations of the in-vehicle device 20 and the electronic key 10 at that time will be described with reference to FIG.
As shown in the figure, the repeater 101 receives the wake signal Swk, both measurement signals Srs1 and Srs2, and the challenge signal Scc via its own transmission / reception unit 101a. The repeater 101 transmits the wake signal Swk and the like received through the transmission / reception unit 101a from the transmission / reception unit 101c located at a position away from the vehicle through the cable 101b. Thus, the wake signal Swk and the like are relayed to a position away from the vehicle through the repeater 101. At this time, the repeater 101 does not imitate the signal strength of various signals. That is, even if the repeater 101 receives both measurement signals Srs1 and Srs2 having different RSSIs through the transmission / reception unit 101a, the repeater 101 transmits both measurement signals Srs1 and Srs2 with the same signal strength through the transmission / reception unit 101c.

  At this time, the electronic key control unit 11 recognizes the RSSI of both measurement signals Srs1 and Srs2 from the transmission / reception unit 101c through the RSSI detection circuit 16. At this time, as described above, the signal strengths of both measurement signals Srs1 and Srs2 are the same. Therefore, the electronic key control unit 11 is an unauthorized communication using a repeater, assuming that the difference between the RSSI of the first measurement signal Srs1 and the RSSI of the second measurement signal Srs2 is equal to or less than a threshold value. Judging.

  Here, for example, when the electronic key 10 possessed by the user moves, the distance between the transmission / reception unit 101c and the electronic key 10 changes. The RSSI of the radio signal from the transmission / reception unit 101 c received by the electronic key 10 is inversely proportional to the distance between the transmission / reception unit 101 c and the electronic key 10.

  Therefore, when the distance between the electronic key 10 and the transmission / reception unit 101c changes due to the user's movement during the period after the reception of the first measurement signal Srs1 and before the reception of the second measurement signal Srs2, the relay is performed. In spite of unauthorized communication using a device, there is a possibility that a difference occurs in the RSSI between the measurement signals Srs1 and Srs2.

  Specifically, as shown at position P1 in FIG. 4, when the electronic key 10 is present on the circumference of the first transmission area 31, the RSSI difference between the measurement signals Srs1 and Srs2 has a threshold value. Over. On the other hand, when the repeater 101 is used, when the electronic key 10 exists at the position P2 in FIG. 4 and the electronic key 10 moves to the side opposite to the transmission / reception unit 101c within a certain period T1, the second measurement signal The RSSI of Srs2 becomes smaller than the RSSI of the first measurement signal Srs1, and the difference between them may exceed the threshold value.

  When the repeater 101 is used, in order for the difference between both RSSIs to exceed the threshold value, the movement amount of the electronic key 10 is represented by the difference between the radii of both the transmission areas 31 and 32, “radius R1-radius R2. It is necessary to exceed a certain distance.

  In that respect, in the present embodiment, the RSSI difference between the two measurement signals Srs1, Srs2 does not exceed the threshold value. That is, the fixed time T1 related to the transmission of both measurement signals Srs1 and Srs2 is set so that the difference between both RSSIs does not exceed the threshold value. The fixed time T1 is set to a time that the electronic key 10 cannot move by “radius R1−radius R2”. In calculating this fixed time T1, for example, the maximum movement speed Vmax when the user walks is determined. Then, the predetermined time T1 is calculated by dividing "radius R1-radius R2" by the maximum moving speed Vmax. For example, when the maximum moving speed Vmax is 5 km / h and “radius R1−radius R2” is 40 cm, the predetermined time T1 is about 300 ms. Thereby, even if the electronic key 10 moves at the maximum moving speed Vmax of 5 km / h, the moving distance is 40 cm. In this case, the difference in RSSI between the measurement signals Srs1 and Srs2 is the same as the threshold value. Therefore, since the difference between both RSSIs is equal to or less than the threshold value, it is determined that the communication is unauthorized using the repeater. Even when the electronic key 10 moves in this way, it is determined that the communication is illegal using the repeater correctly.

  Next, operations of the electronic key control unit 11 and the in-vehicle control unit 21 will be described with reference to the flowchart of FIG. This flowchart is repeatedly executed, for example, when the engine is stopped.

  First, when the in-vehicle control unit 21 recognizes that the lock switch 36 or the engine switch 33 has been operated, the wake signal Swk and the first measurement signal Srs1, and the wake signal Swk and the second measurement signal Srs2 are continuously generated. (S101 and S102). When receiving the various signals, the electronic key control unit 11 recognizes the RSSI of both measurement signals Srs1 and Srs2 (S103). Then, the electronic key control unit 11 transmits an ACK signal Sac (S104). When receiving the ACK signal Sac, the in-vehicle controller 21 transmits a challenge signal Scc (S105). When receiving the challenge signal Scc, the electronic key control unit 11 transmits a response signal Sre (S106). When the in-vehicle control unit 21 receives the response signal Sre and determines that the response verification and the ID code verification have been established (S107), the communication with the current electronic key 10 is performed based on the RSSI information included in the response signal Sre. It is determined whether or not it is an unauthorized one using a repeater (S108). If the in-vehicle control unit 21 determines that the communication is not unauthorized using the repeater (NO in S108), the vehicle-mounted control unit 21 starts the engine or unlocks the vehicle door (S109). On the other hand, if the in-vehicle control unit 21 determines that the communication is unauthorized using the repeater (YES in S108), the in-vehicle control unit 21 ends the flowchart without starting the engine or unlocking the vehicle door.

As described above, according to the embodiment described above, the following effects can be obtained.
(1) Both measurement signals Srs1 and Srs2 having different signal intensities are transmitted from the in-vehicle device 20. When the difference between the RSSIs of these signals is equal to or less than the threshold value, it is determined that the communication is unauthorized using the repeater 101. This is because the repeater 101 does not imitate the signal strength of the radio signal, and therefore when the repeater 101 is used, the difference in RSSI between the measurement signals Srs1 and Srs2 transmitted from the repeater 101 is close to zero. Because it does. However, even when the repeater 101 is used, the RSSI of both measurement signals Srs1 and Srs2 detected through the RSSI detection circuit 16 is different due to movement of the electronic key 10 carried by the user. In this regard, in the above configuration, both measurement signals Srs1 and Srs2 are transmitted within a predetermined time T1. The shorter the fixed time T1 is set, the smaller the distance that the electronic key 10 can move during that time, so the difference in RSSI between the measurement signals Srs1, Srs2 becomes smaller. From such a viewpoint, even when both measurement signals Srs1 and Srs2 having the same signal intensity are transmitted from the repeater 101, the measurement signals Srs1 and Srs2 accompanying the movement of the electronic key 10 are transmitted for a certain time T1. The RSSI difference is set so small that it is equal to or less than the threshold value. As a result, even when the electronic key 10 is moved, it is correctly determined that the communication is unauthorized using the repeater.

  (2) The constant time T1 is calculated by dividing the radius difference “radius R1−radius R2” between the transmission areas 31 and 32 by the maximum moving speed Vmax. Therefore, it is possible to prevent the electronic key 10 from moving beyond the distance represented by “radius R1−radius R2” within a predetermined time T1. As a result, when both measurement signals Srs1, Srs2 having the same signal intensity are transmitted from the repeater 101, the RSSI difference between the two measurement signals Srs1, Srs2 is determined by the movement of the electronic key 10. Can be suppressed from being erroneously determined that the communication is not unauthorized using the repeater 101.

  (3) The detection result of the RSSI detection circuit 16 is transmitted to the in-vehicle device 20 through the response signal Sre. The in-vehicle device 20 can determine whether or not the communication is unauthorized using a repeater based on the detection result of the RSSI detection circuit 16 included in the response signal Sre. As described above, by making the above determination in the in-vehicle device 20, the processing related to the determination in the electronic key 10 can be omitted.

In addition, the said embodiment can be implemented with the following forms which changed this suitably.
In the above embodiment, the electronic key 10 transmits the detection result included in the response signal Sre without making any judgment on the detection result of the RSSI detection circuit 16. However, based on the detection result of the RSSI detection circuit 16, the electronic key control unit 11 may determine whether the communication is unauthorized communication using a repeater (S108). The electronic key 10 includes the determination result in a wireless signal and transmits it to the in-vehicle device 20. The in-vehicle device 20 determines whether to unlock the vehicle door or start the engine based on the determination result included in the wireless signal.

The RSSI detection circuit 16 in the above embodiment may be provided independently of the LF receiver 12.
In the above embodiment, both measurement signals Srs1 and Srs2 are transmitted from the in-vehicle device 20 to the electronic key 10. However, the measurement signals Srs1 and Srs2 may be transmitted from the electronic key 10 to the in-vehicle device 20. In this case, the RSSI detection circuit 16 is provided in the in-vehicle device 20 in the in-vehicle receiving unit 24 or independently of the in-vehicle receiving unit 24. Also in this configuration, since the RSSI of both measurement signals Srs1 and Srs2 changes with the movement of the electronic key 10, the same effect as the above embodiment can be obtained.

  In the above embodiment, both measurement signals Srs1 and Srs2 are transmitted after the wake signal Swk, respectively. However, after transmitting a single wake signal Swk, both measurement signals Srs1 and Srs2 may be transmitted continuously. Further, the wake signal Swk may be omitted.

  In the above embodiment, the RSSI information is transmitted by being included in the response signal Sre. However, an RSSI information signal including only RSSI information may be transmitted separately from the response signal. Further, RSSI information may be included in the ACK signal Sac.

  In the above embodiment, two measurement signals Srs1 and Srs2 are transmitted. However, if there are a plurality of signals, three or more measurement signals may be transmitted. In this case, it is possible to accurately determine whether or not the communication is unauthorized using the repeater based on the difference in RSSI between the measurement signals.

  In the above embodiment, the outside transmission unit 22 and the inside transmission unit 23 are provided. However, a common transmission unit inside and outside the vehicle may be provided. This transmission unit forms a transmission area inside and outside the vehicle interior.

  -You may reverse the process of step S107 and step S108 in the said embodiment. In this case, when it is determined that the communication is unauthorized using the repeater, the flowchart is terminated without performing response verification and ID code verification.

  In the above embodiment, the in-vehicle device 20 transmits an LF band radio signal, and the electronic key 10 transmits a UHF band radio signal. However, the frequency band of the radio signal transmitted and received between the in-vehicle device 20 and the electronic key 10 is not limited to these.

  In the above embodiment, the in-vehicle device 20 that is a control target performs locking and unlocking of the vehicle door and the like through wireless communication with the electronic key 10. However, the control target is not limited to the in-vehicle device 20 and may be, for example, a residential door device. Even in this case, the unauthorized communication using the repeater can be prevented as in the above embodiment.

Next, the technical idea that can be grasped from the embodiment will be described together with the effects.
(A) In the electronic key system according to claim 3, the signal strength information signal is a response signal including an ID code unique to the electronic key in addition to a detection result of the detection unit, and the control target is When the response signal is received, the ID code included in the signal is collated with the ID code stored in advance, and when the ID code is collated, the determination unit The electronic key system which judges whether it is unauthorized communication which used the repeater based on the detection result of the said detection part contained.

  According to this configuration, it is determined whether or not the communication is unauthorized using the repeater when the ID code verification is established. Thereby, the frequency | count of the judgment can be reduced.

  DESCRIPTION OF SYMBOLS 1 ... Electronic key system, 10 ... Electronic key, 20 ... In-vehicle apparatus (control object), 21 ... In-vehicle control part (determination part), 16 ... RSSI detection circuit (detection part).

Claims (3)

In an electronic key system in which control of the control target is executed through a wireless signal transmitted and received between the control target and the electronic key,
The control object or the electronic key transmits a plurality of radio signals having different signal strengths within a predetermined time,
A detection unit that is provided in the electronic key or the control target and detects a signal intensity of each radio signal transmitted from the control target or the electronic key;
A threshold which is provided on the control object or the electronic key and is determined based on a difference in signal strength between the radio signals to be transmitted is defined as a difference in signal strength between the radio signals recognized through the detection unit. When it exceeds, it is determined that the communication is not an unauthorized communication using a repeater, and the execution of the control target is permitted, and when it is equal to or less than the threshold, the communication is determined to be an unauthorized communication using a repeater. A determination unit that prohibits execution of the target control,
Even when the signal strength of each wireless signal is the same through the repeater during the certain time, the difference in signal strength of each wireless signal from the repeater accompanying the movement of the electronic key within the certain time is Electronic key system set to be below threshold. The electronic key system according to claim 1.
The electronic key system in which the predetermined time is calculated by dividing a difference in signal arrival distance according to signal strength of each wireless signal by an assumed maximum moving speed of the user. The electronic key system according to claim 1 or 2,
The detection unit is provided in the electronic key and detects signal intensities of a plurality of measurement signals that are the plurality of radio signals from the control target,
The electronic key includes a signal strength information signal including the signal strength of each measurement signal recognized through the detection unit, and transmits the signal strength information signal.
The determination unit is an electronic device that is provided in the control target and determines whether or not the communication is illegal communication using a repeater based on the signal strength of each measurement signal included in the signal strength information signal. Key system.

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