Distance measuring device
A technology of distance measuring device and switching circuit, which is applied in measuring device, transportation and packaging, radio wave measurement system, etc., and can solve the problem that the exact distance between the key and the car cannot be obtained
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no. 1 Embodiment approach
[0020] figure 1 It is a block diagram showing the configuration of a distance measuring system including the distance measuring device according to the first embodiment.
[0021] In recent years, many vehicles have adopted a keyless entry device that facilitates locking and unlocking of the vehicle. This technology utilizes the communication between the vehicle key (key) and the vehicle to lock and unlock the doors. In addition, in recent years, a smart door opening system that can lock and unlock a door or start an engine with a smart key without touching the key has also been adopted.
[0022] However, it often happens that an attacker breaks into the communication between the key and the car to steal the vehicle. As a defense against the above-mentioned attack (so-called relay attack), a measure has been considered in which the distance between the key and the car is measured, and when it is determined that the distance is greater than a predetermined distance, control of...
no. 2 Embodiment approach
[0065] Next, a second embodiment will be described.
[0066] Figure 4 It is a block diagram showing the configuration of the distance measuring device according to the second embodiment. In addition, in Figure 4 in, for with Figure 3A The same configurations are given the same symbols and descriptions thereof are omitted.
[0067] The distance measuring device 1A of this embodiment is configured from Figure 3A The resistor R1 is deleted from the distance measuring device 1, and the switch 17 is replaced by a switch 17A. Other configurations are the same as those of the first embodiment.
[0068] The switch 17A of the present embodiment is, for example, a switch using a transistor with a large on-resistance. Accordingly, the input / output impedance of the switch 17A is made higher than the impedance of the antenna 16 .
[0069] As a result, the distance measuring device 1A can obtain the same effect as that of the first embodiment without using the resistor R1 of the ...
no. 3 Embodiment approach
[0071] Next, a third embodiment will be described.
[0072] Figure 5 It is a block diagram showing the configuration of the distance measuring device of the third embodiment. In addition, in Figure 5 in, for with Figure 3A The same configurations are given the same symbols and descriptions thereof are omitted.
[0073] Such as Figure 5 As shown, the distance measuring device 1B of this embodiment is configured such that, for Figure 3A Signal processing circuits 31 and 32 are added to the distance measuring device 1 . Specifically, a signal processing circuit 31 is added between the switch 18 and the receiving circuit 11 , and a signal processing circuit 32 is added between the switch 19 and the transmitting circuit 10 .
[0074] The signal processing circuits 31 and 32 are circuits for performing desired signal processing, and are composed of amplifiers or attenuators, for example. In this way, in the distance measuring device 1B, other circuits (signal processing ...
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