JP5768645B2 - Smart systems for vehicles - Google Patents

Description

  The present invention relates to a smart system for a vehicle.

  Conventionally, as shown in FIG. 7A, when a user 91 of a vehicle 90 approaches the vehicle 90 with the portable device 92, the request signal transmitted from the vehicle 90 is received by the portable device 92, and the portable device 92 Based on the reception of the request signal, an answer signal is transmitted to the vehicle 90. The vehicle 90 receives the answer signal, and then the smart drive (unlocking the door of the vehicle 90 and the vehicle drive device). Smart system technology is known to perform both and / or starting of the system.

  In contrast to such smart system technology, even when the portable device 92 is far away from the vehicle 90, communication between the portable device 92 and the vehicle 90 is indirectly realized using a repeater. The relay station attack that makes smart driving may be a problem.

  In the relay station attack, as shown in FIG. 7B, the RA repeater 94 is disposed within the communicable range 93 of the vehicle 90, and the RA repeater 95 is disposed in the vicinity of the portable device 91. The RA request signal is received by the RA repeater 94, converted into a relay signal suitable for long-distance communication, and transmitted to the RA repeater 95. The relay signal is received by the RA repeater 95, and the request signal is received. The data is restored to be transmitted to the portable device 92. Thereby, an answer signal is transmitted from the portable device 92, and the vehicle 90 may receive this answer signal and perform smart driving.

  As a countermeasure against such a relay station attack in which an RA repeater intervenes in a smart system, Patent Document 1 discloses a delay in the time from transmission of a request signal to reception of an answer signal due to the intervention of an RA repeater. If the time from the transmission of the request signal to the reception of the answer signal exceeds the effective time value assumed in the normal operation of the smart system, it is determined that there is an intervention of the RA repeater. A technique for prohibiting driving is described.

Japanese Patent Laid-Open No. 2003-13644

  However, in the technique of Patent Document 1, the time from when the vehicle transmits a request signal until it receives an answer signal, whether the portable device is located near the vehicle or the portable device is located far from the vehicle. Is very short, it is difficult to increase the time measurement to such an extent that it can be determined whether or not the portable device is away from the vehicle.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a technology capable of defending against a relay station attack even when measurement of the time for receiving an answer signal after transmitting a request signal is not highly accurate in a smart system. And

In order to achieve the above object, an invention according to claim 1 is a smart system that performs one or both of unlocking a vehicle door and starting a vehicle drive device as a smart drive, and is installed in the vehicle. An in-vehicle system (10) and a portable device (20) carried by the user. The in-vehicle system (10) includes an in-vehicle transmission antenna unit (2) and an in-vehicle side control unit (1) mounted in a vehicle. ), The in-vehicle side control unit (1) wirelessly transmits a predetermined request signal from the in-vehicle side transmission antenna unit (2), and the portable device (20) has a portable side reception antenna unit (21). The portable-side transmission antenna (24) and the portable-side control unit (26), the portable-side control unit (26) is based on the reception of the request signal by the portable-side reception antenna unit (21), Answer A signal is wirelessly transmitted from the portable transmission antenna (24) , and the vehicle-mounted control unit (1) performs the smart drive based on the wireless reception of the answer signal, and the vehicle-mounted transmission antenna unit ( 2) has two in-vehicle side transmission antennas (2b, 2c) each composed of a loop coil, and the two in-vehicle side transmission antennas (2b, 2c) are methods of the opening surface of each loop coil. Arranged so that the line directions are orthogonal to each other, the request signals are transmitted with a predetermined phase difference from each other, and the mobile-side receiving antenna unit (21) is composed of two mobile sides each composed of a loop coil The mobile-side control unit (26) includes the receiving antennas (21b, 21c), and the mobile-side control unit (26) includes the two mobile-side receiving antennas (21b, 21c) with the predetermined phase difference from each other. The answer signal is allowed to be wirelessly transmitted based on the reception of the strike signal, and the two portable-side reception antennas (21b, 21c) are different from each other in the phase difference different from the predetermined phase difference. The smart system is characterized by prohibiting wireless transmission of the answer signal based on the reception of.

  As described above, in the in-vehicle system (10), two polarized waves having different polarization planes are used, the request signal is transmitted so as to have a predetermined phase difference between the two polarized waves, and the portable device (20) is different. When a request signal is received at two polarization planes and the absolute value of the phase difference between the request signals received at the two different polarization planes is a predetermined value (absolute value of the predetermined phase difference), an answer signal is transmitted. If not, transmission of the answer signal is prohibited. Therefore, it is possible to prevent a relay station attack that does not perform relay based on the phase difference of the request signal. Therefore, in the smart system, it is possible to protect against the relay station attack even if the time for receiving the answer signal after transmitting the request signal is not highly accurate.

  Further, according to a second aspect of the present invention, in the smart system according to the first aspect, the predetermined phase difference is 90 degrees. The request signal is circularly polarized, the detection error of the phase difference on the portable device side is minimized, and the lowest received voltage on the portable device side can be maximized.

  In addition, the code | symbol in the bracket | parenthesis in the said and the claim shows the correspondence of the term described in the claim, and the concrete thing etc. which illustrate the said term described in embodiment mentioned later. .

It is a block diagram of the smart system which concerns on embodiment of this invention. 3 is a configuration diagram of an LF transmission antenna unit 2. FIG. 2 is a configuration diagram of an LF reception antenna unit 21. FIG. It is a flowchart of the process which smart ECU performs. It is a flowchart of the process which a portable side control part performs. It is a figure which shows the outline | summary of the relay station attack of this embodiment. It is a figure which shows the outline | summary of a smart system and a relay station attack.

  Hereinafter, an embodiment of the present invention will be described. FIG. 1 shows a configuration of a smart system according to the present embodiment. This smart system unlocks a vehicle door and starts a vehicle drive device (for example, an engine or an electric motor) as a smart drive, and includes an in-vehicle system 10 mounted on the vehicle and a portable device carried by the user. 20.

  The in-vehicle system 10 includes a smart ECU 1, an LF transmission antenna unit 2, an LF modulation unit 3, an RF reception antenna 4, an RF demodulation unit 5, a sensor 6, and an actuator 7.

  The LF modulation unit 3 is a circuit that modulates a signal of LF data output from the smart ECU 1 into a request signal in the LF wave band and outputs the request signal to the LF transmission antenna unit 2. As the modulation method, for example, an ASK (Amplitude Shift Keying) modulation method or the like is adopted.

  The LF transmission antenna unit 2 (corresponding to an example of the in-vehicle transmission antenna unit) wirelessly transmits a signal (LF radio wave) in the LF wave band. FIG. 2 shows the configuration of the LF transmission antenna unit 2 in detail. The LF receiving antenna unit 2 includes a loop antenna 2b (corresponding to one of two in-vehicle transmission antennas) formed of a core 2a made of a material having high magnetic permeability such as ferrite and a loop coil wound around the core 2a. And a loop antenna 2c (corresponding to one of the two in-vehicle transmission antennas) formed of another loop coil wound around the core 2a a plurality of times.

  As shown in FIG. 2, the loop antennas 2b and 2c are wound around the same core 2a in different directions. Thereby, the normal direction 31b of the opening surface of the loop coil of the loop antenna 2b and the normal direction 31c of the opening surface of the loop coil of the loop antenna 2c are arranged so as to be orthogonal to each other. As a result, the radio wave (linearly polarized wave) transmitted from the loop antenna 2b and the radio wave (linearly polarized wave) transmitted from the loop antenna 2c are orthogonal to each other, and thereby , Polarization diversity can be realized.

  The request signal output from the LF modulation unit 3 is delayed by the phase delay amount θ1 by the phase delay circuit 2d and then input to the loop antenna 2b, and after being delayed by the phase delay amount θ2 by the phase delay circuit 2e, the loop Input to the antenna 2c.

  Accordingly, the radio wave of the request signal transmitted from the loop antenna 2b and the radio wave of the request signal transmitted from the loop antenna 2c are orthogonal to each other in the polarization direction and have a phase difference of θ1−θ2.

  The phase delay amounts θ1 and θ2 are determined in advance, and may be any value as long as the difference between θ1 and θ2 is not an integral multiple of 180 degrees, but the difference between θ1 and θ2 is 90 degrees + 180. It is more desirable that the degree is xn (where n is an integer). The reason will be described later.

  The RF receiving antenna 4 is an antenna for wirelessly receiving an RF waveband signal (RF radio wave). The RF demodulator 5 is a circuit that demodulates an answer signal in the RF wave band received by the RF receiving antenna 4 and outputs it to the smart ECU 1 as an RF data signal.

  The sensor 6 is a sensor that is attached to a door handle portion or the like of the door of the vehicle, detects a user's operation of placing a hand on the door, and outputs a detection result to the smart ECU 1, and can be realized as a touch sensor, for example. is there.

  The actuator 7 is an actuator that is a target of smart drive, and includes a starter motor of a vehicle engine (or an engine ECU that controls the starter motor), a door lock mechanism that locks and unlocks the door of the vehicle (controls the door lock mechanism). Door ECU).

  The smart ECU 1 is an electronic control unit that performs smart driving based on communication with the portable device 20 by exchanging signals with the LF modulation unit 3, the RF demodulation unit 5, the sensor 6, and the actuator 7.

  The smart ECU 1 is realized as a microcomputer including a CPU, a RAM, a ROM, an I / O, and the like, and the CPU executes a program recorded in the ROM, thereby realizing various processes using the RAM as a work area. . Below, the process which CPU performs is described as a process of smart ECU1.

  The portable device 20 includes an LF reception antenna unit 21, an LF demodulation unit 22, a phase detection circuit 23, an RF transmission antenna 24, an RF modulation unit 25, and a portable side control unit 26.

  The LF reception antenna unit 21 (corresponding to an example of the mobile-side reception antenna unit) receives an LF waveband request signal transmitted from the in-vehicle system 10. FIG. 3 shows the configuration of the LF reception antenna unit 21.

  The LF receiving antenna unit 21 is a loop antenna 21b (corresponding to one of two mobile-side receiving antennas) composed of a core 21a made of a material having high magnetic permeability such as ferrite and a loop coil wound around the core 21a a plurality of times. And a loop antenna 21c (corresponding to one of the two mobile-side receiving antennas) composed of another loop coil wound around the core 21a a plurality of times.

  As shown in FIG. 2, the loop antennas 21b and 21c are wound around the same core 21a a plurality of times in different directions. Thus, the normal direction 32b of the opening surface of the loop coil of the loop antenna 21b and the normal direction 32c of the opening surface of the loop coil of the loop antenna 21c are arranged so as to be orthogonal to each other. With this configuration, polarization diversity can be realized by the loop antennas 21b and 21c.

  The LF demodulator 22 demodulates one of the LF waveband request signals received by the loop antennas 21b and 21c of the LF reception antenna unit 21 (for example, one having a higher reception intensity) or both signals to demodulate the LF data. This is a circuit that outputs the signal to the portable control unit 26 as a signal. As a demodulation method, for example, an ASK demodulation method is adopted.

  The phase detection circuit 23 compares the phase of the radio wave of the request signal received by the loop antenna 21b with the phase of the radio wave of the request signal received by the loop antenna 21b, and outputs a signal having a voltage corresponding to the phase difference between the two. 26 is a well-known circuit that outputs to H.26.

  The RF transmission antenna 24 is an antenna for wirelessly transmitting an RF wave answer signal (RF radio wave). The RF modulation unit 25 is a circuit that modulates an RF data signal output from the portable control unit 26 into an RF wave answer signal and outputs the RF signal to the RF transmission antenna 24.

  The portable side control unit 26 is realized as a microcomputer including a CPU, a RAM, a ROM, an I / O, and the like. When the CPU executes a program recorded in the ROM, various processes are performed using the RAM as a work area. Is realized. Hereinafter, processing executed by the CPU will be described as processing of the portable control unit 26.

  Hereinafter, the operation of the smart system having such a configuration will be described. FIG. 4 is a flowchart of processing executed by the smart ECU 1 of the smart ECU 1, and FIG. 5 is a flowchart executed by the portable side control unit 26 of the portable device 20.

  First, in step 105, the smart ECU 1 detects a polling timing that is periodically (for example, 1 second cycle) and an operation in which the user touches the door as a transmission timing to wait until the transmission timing comes. There is a timing.

  When the transmission timing arrives, the process proceeds to step 110 where predetermined LF data is generated and output to the LF modulation unit 3. As a result, the LF data is modulated by the LF modulation unit 3 and wirelessly transmitted from the LF transmission antenna unit 2 as a request signal in the LF waveband. Since signals in the LF wave band are severely attenuated, they can be received only in the vicinity of the vehicle. Following step 110, in step 120, reception of an RF band answer signal is awaited.

  Here, the radio wave of the request signal transmitted from the LF transmission antenna unit 2 by the processing of step 110 will be described. As already described, in the LF transmission antenna unit 2, the loop antennas 2b and 2c transmit the request signals output from the LF modulation unit 3 with polarizations orthogonal to each other and with a predetermined phase difference θ1 to θ2. To do.

  Here, as shown in FIG. 6A, the portable device 20 is in the vicinity of the vehicle on which the in-vehicle system 10 is mounted, and can receive the request signal 81 in the LF wave band transmitted from the in-vehicle system 10 as described above. Suppose.

  In this case, in the LF reception antenna unit 21 of the portable device 20, the loop antennas 21 b and 21 c receive the radio waves of the request signal 81 transmitted from the loop antennas 2 b and 2 c of the in-vehicle system 10.

  At this time, since the normal direction 32b of the opening surface of the loop coil of the loop antenna 21b and the normal direction 32c of the opening surface of the loop coil of the loop antenna 21c are orthogonal to each other, the request signal received by the loop antenna 21b The absolute value of the phase difference α1-α2 between the phase α1 of the radio wave and the phase α2 of the radio wave of the request signal received by the loop antenna 21c is the absolute value of the phase difference θ1-θ2 in the loop antennas 2b, 2c of the in-vehicle system 10 Will be the same. This is the same regardless of the posture of the loop antennas 21b and 21c with respect to the loop antennas 2b and 2c. However, when the surface constituted by the normal directions 31b and 31c and the surface constituted by the normal directions 32b and 32c are orthogonal to each other, the absolute value of the phase difference α1-α2 and the phase difference θ1- The absolute value of θ2 is exceptionally different. In the present embodiment, the surface constituted by the normal directions 31b and 31c and the surface constituted by the normal directions 32b and 32c were not orthogonal to each other (for example, both surfaces were parallel to each other). ).

  Therefore, the phase detection circuit 23 outputs a signal having a voltage corresponding to the phase difference α1-α2 between the signal received from the loop antenna 21b and the signal received from the loop antenna 21b to the portable control unit 26.

  The LF demodulator 22 demodulates one or both of the LF waveband request signals received from the loop antennas 21b and 21c (for example, one having a higher reception intensity) and transmits it to the portable control unit 26 as an LF data signal. Output.

  Then, the portable control unit 26 determines that it has been received from the state of waiting until receiving the signal of LF data in Step 210, and proceeds to Step 220. In step 220, the absolute value | α1-α2 | of the phase difference α1-α2 is specified based on the voltage of the signal received from the phase detection circuit 23, and the absolute value | α1-α2 | It is determined whether or not the absolute value | θ1−θ2 | of θ2 is the same as a predetermined value (within a predetermined minute error range). In this example, it is determined that the absolute value | α1−α2 | and the predetermined value (absolute value | θ1−θ2 |) are the same, and the process proceeds to step 230.

  In step 230, it is determined whether or not the LF data included in the received LF waveband signal is normal by a known method (for example, whether or not it matches the normal data). Since the portable device 20 is compatible with the in-vehicle system 10, the LF data included in the LF waveband request signal transmitted from the in-vehicle system 10 is determined to be legitimate, and the process proceeds to step 240.

  In step 240, predetermined RF data is created and output to the RF modulation unit 25. However, this RF data includes key data for use in data verification in the in-vehicle system 10. As a result, the RF data is modulated by the RF modulation unit 25 and wirelessly transmitted as an answer signal 82 in the RF wave band from the RF transmission antenna 24. The signal of the RF wave band reaches farther than the signal of the LF wave band. Following step 240, processing returns to step 210.

  If the received LF waveband signal 81 is not from the in-vehicle system 10, it is temporarily determined in step 220 that the absolute value | α1-α2 | of the phase difference is the same as the predetermined value, and the process proceeds to step 230. Even so, in Step 230, it is determined that the LF data included in the received signal in the LF waveband is not normal, and execution of Step 240 is avoided, and the process returns to Step 210.

  When the answer signal 82 of the RF wave band including the RF data is transmitted as described above, the RF receiving antenna 4 of the in-vehicle system 10 receives the answer signal 82, and the RF demodulator 5 demodulates the answer signal 82. And it outputs to the vehicle side control part 13 as a signal of RF data.

  Then, the vehicle side control part 13 determines with having received RF data by step 120, and progresses to step 125. FIG. In step 125, in order to determine whether or not the received RF data is legitimate, the key data in the RF data is collated with predetermined collation data.

  Subsequently, in step 130, based on the result of the collation in step 125, whether or not the RF data is genuine is determined by a known method (for example, whether the key data matches the collation data). judge.

  Since the portable device 20 that has transmitted the RF waveband signal including the RF data is compatible with the in-vehicle system 10, the RF data is determined to be legitimate, and the process proceeds to step 140.

  If the received signal in the RF waveband is not from the portable device 20, it is determined in step 130 that the received RF data is not authentic, and the processing is skipped to step 140 and the process is shifted to step 105. return. Thereby, smart driving is prohibited.

  In step 140, smart driving is started. More specifically, the door is unlocked by controlling the actuator 7, and the engine is started based on the engine start operation (for example, pressing of the engine start button) by the user. After step 150, the process returns to step 105.

  In this way, when the in-vehicle system 10 and the portable device 20 communicate with each other in a normal manner without the intervention of the RA repeater, the portable device 20 enters the communicable range 53, Smart driving is realized.

  Here, a case where a relay station attack is attempted will be described. In the relay station attack, as shown in FIG. 7B, the RA repeater 94 is disposed within the communicable range 53 of the LF waveband signal, and the RA repeater 95 is disposed in the vicinity of the portable device 20, so The RA repeater 94 receives the LF waveband request signal 81 transmitted from the system 10, converts the frequency into an RF waveband signal, transmits the signal to the RA relay 95, and the RF waveband signal is transmitted to the RA repeater. 95 is received, returned to the request signal 83 of the LF wave band, and transmitted to the portable device 20.

  However, it is considered that the receiving antenna for the LF wave band of the RA repeater 94 does not have two receiving loop antennas whose directions perpendicular to the aperture plane are orthogonal to each other. It cannot be detected. Furthermore, it is considered that the LF waveband transmission antenna of the RA repeater 95 does not include two transmission loop antennas whose directions perpendicular to the aperture plane are orthogonal.

  Therefore, even if the loop antennas 21b and 21c of the portable device 20 receive the request signals relayed by the RA repeaters 94 and 95, the absolute value | α1−α2 of the phase difference of the request signals received by the loop antennas 21b and 21c. | Becomes zero and does not become the same as the absolute value (predetermined value) | θ1-θ2 | of the phase difference of the request signals transmitted by the loop antennas 2b and 2c of the in-vehicle device 10.

  Therefore, the mobile-side control unit 26 determines that it has been received from the state of waiting until receiving the signal of LF data in Step 210, and proceeds to Step 220. In step 220, the absolute value | α1-α2 | (which is zero in this example) of the phase difference α1-α2 is specified based on the voltage of the signal received from the phase detection circuit 23, and this absolute value | It is determined whether or not α1−α2 | is the same as a predetermined value (within a predetermined minute error range) predetermined as the absolute value | θ1−θ2 | of the phase difference θ1−θ2. In this example, it is determined that the absolute value | α1−α2 | and the predetermined value (absolute value | θ1−θ2 |) are not the same, the execution of step 240 is avoided, and the process returns to step 210. Accordingly, when there is a relay station attack, the answer signal 82 is not transmitted from the portable device 20, so that smart driving is prohibited.

  As described above, the LF transmission antenna unit 2 of the in-vehicle system 10 has two loop antennas 2b and 2c each configured by a loop coil, and the two loop antennas 2b and 2c are respectively connected to the respective loop coils. The normal directions 31b and 31c of the opening surface are arranged so as to be orthogonal to each other, and the request signals are transmitted with a predetermined phase difference θ1-θ2. In addition, the LF reception antenna unit 21 of the portable device 20 includes two loop antennas 21b and 21c each formed of a loop coil, and the portable-side control unit 26 includes two LF reception antennas 21b and 21c that are predetermined to each other. Based on the fact that the request signal is received at the phase difference | θ1-θ2 |, the answer signal is allowed to be transmitted wirelessly (step 220 → YES), and the two loop antennas 21b and 21c have a predetermined phase difference | Based on the fact that the request signal is received with a phase difference different from θ1-θ2 |, the wireless transmission of the answer signal is prohibited (step 220 → NO).

  As described above, in the in-vehicle system 10, two polarized waves having different polarization planes are used, and the request signal is transmitted so as to have a predetermined phase difference between the two polarized waves. The request signal is received at, and the answer signal is allowed to be transmitted only when the absolute value of the phase difference of the request signals received at the two different polarization planes is a predetermined value (the absolute value of the predetermined phase difference). Therefore, it is possible to prevent a relay station attack that does not perform relaying based on the phase difference of request signals. Therefore, in the smart system, it is possible to protect against the relay station attack even if the time for receiving the answer signal after transmitting the request signal is not highly accurate.

  In the present embodiment, the radio wave of the request signal transmitted from the loop antenna 2b and the radio wave of the request signal transmitted from the loop antenna 2c are orthogonal to each other and have a phase difference of θ1−θ2. . As described above, the phase difference θ1−θ2 is more preferably 90 degrees + 180 degrees × n (where n is an integer). There are two reasons for this.

  The first reason is that when the difference between θ1 and θ2 is 90 degrees + 180 degrees × n (where n is an integer), the phase detection circuit 23 of the portable device 20 outputs the highest voltage. This is because the detection error is the smallest.

  The second reason is as follows. Due to the interference between the electromagnetic wave from the loop antenna 2b and the electromagnetic wave from the loop antenna 2c, the minimum reception voltage at the LF reception antenna unit 21 varies depending on the position of the LF reception antenna unit 21 (loop antennas 21b and 21c). This variation is the smallest when the difference between θ1 and θ2 is 90 degrees + 180 degrees × n (where n is an integer). Therefore, in this case, the lowest reception voltage at the LF reception antenna unit 21 can be maximized.

(Other embodiments)
As mentioned above, although embodiment of this invention was described, the scope of the present invention is not limited only to the said embodiment, The various form which can implement | achieve the function of each invention specific matter of this invention is included. It is.

  For example, in the above embodiment, the request signal is transmitted and received as a signal in the LF wave band, but may be transmitted and received as a signal in a frequency band other than the LF wave band.

1 Smart ECU
2 LF transmitting antenna unit 2a, 21a Core 2b, 2c, 21a, 21c Loop antenna 2d, 2e Phase delay circuit 3 LF modulating unit 4 RF receiving antenna 5 RF demodulating unit 6 Sensor 7 Actuator 10 In-vehicle system 20 Portable device 21 LF receiving antenna Unit 22 LF demodulation unit 23 phase detection circuit 24 RF transmission antenna 25 RF modulation unit 26 portable side control unit 81, 83 request signal 82 answer signal 94, 95 RA repeater

Claims (2)

A smart system that performs one or both of unlocking a vehicle door and starting a vehicle drive device as a smart drive,
An in-vehicle system (10) mounted on a vehicle, and a portable device (20) carried by a user;
The vehicle-mounted system (10) includes a vehicle-mounted transmission antenna unit (2) and a vehicle-mounted control unit (1) mounted on a vehicle, and the vehicle-mounted control unit (1) sends a predetermined request signal to the vehicle-mounted system. Wireless transmission from the side transmission antenna (2),
The portable device (20) includes a portable reception antenna unit (21) , a portable transmission antenna (24), and a portable control unit (26), and the portable control unit (26) includes a portable reception antenna. Based on the reception of the request signal by the unit (21), the answer signal is wirelessly transmitted from the portable transmitting antenna (24) ,
The vehicle-mounted side control unit (1) performs the smart drive based on the wireless reception of the answer signal,
The vehicle-mounted transmission antenna unit (2) has two vehicle-mounted transmission antennas (2b, 2c) each formed of a loop coil, and the two vehicle-mounted transmission antennas (2b, 2c) The normal direction of the opening surface of the loop coil is arranged to be orthogonal to each other, and the request signals are transmitted with a predetermined phase difference from each other,
The mobile-side reception antenna unit (21) has two mobile-side reception antennas (21b, 21c) each formed of a loop coil,
The portable control unit (26) wirelessly transmits the answer signal based on the fact that the two portable reception antennas (21b, 21c) receive the request signal with the predetermined phase difference. Permit and prohibit wireless transmission of the answer signal based on the fact that the two portable-side receiving antennas (21b, 21c) receive the request signal with a phase difference different from the predetermined phase difference. A smart system characterized by that.   The smart system according to claim 1, wherein the predetermined phase difference is 90 degrees.

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