Authenticity determination system of responder, identification system, and interrogation unit

1. A responder authenticity determination system, comprising:

a responder that sends a response signal in response to a received signal;

an interrogation signal generator that generates an interrogation signal having a random waveform;

a memory storing a plurality of responder identifications and a plurality of predetermined propagation times in correspondence with each other;

a transmitter that transmits the generated interrogation signal to the responder;

a receiver that receives the response signal from the responder; and

a controller that:

generates a start timer signal upon the transmitter transmitting the generated interrogation signal to the responder,

generates a stop timer signal upon the receiver receiving the response signal,

determines authenticity of the responder based on the received response signal and the random waveform of the generated interrogation signal, and

if the responder is determined to be authentic, determines identification of the responder using a time between the start timer signal and the stop timer signal, and the propagation times stored in the memory to find a corresponding responder identification.

2. The responder authenticity determination system according to claim 1 , wherein:

the interrogation signal generator generates the interrogation signal based on an interrogation request signal; and

the controller revises the received response signal by removing the random waveform from the received response signal, and compares the interrogation request signal with the revised response signal.

3. The responder authenticity determination system according to claim 1 ,

wherein the controller determines authenticity according to whether the random waveform is present in the response signal.

4. The responder authenticity determination system according to claim 1 ,

wherein the responder comprises:

an excitation unit that generates mechanical vibration upon receipt of the interrogation signal;

a surface acoustic wave generator that allows the mechanical vibration to propagate in the responder, so as to generate a surface acoustic wave; and

a converter that converts the surface acoustic wave into an electrical signal and outputs the electrical signal as the response signal.

5. The responder authenticity determination system according to claim 1 ,

wherein the random waveform is a waveform randomized with respect to time.

6. The responder authenticity determination system according to claim 1 ,

wherein the random waveform is a waveform randomized with respect to frequency.

7. The responder authenticity determination system according to claim 1 ,

wherein the random waveform is a waveform randomized with respect to phase.

8. The responder authenticity determination system according to claim 1 ,

wherein the random waveform is a waveform randomized with respect to amplitude.

9. An interrogation unit comprising:

an interrogation signal generator that generates an interrogation signal having a random waveform;

a memory storing a plurality of responder identifications and a plurality of predetermined propagation times in correspondence with each other;

a transmitter that transmits the generated interrogation signal to a responder;

a receiver that receives a response signal from the responder; and

a controller that:

generates a start timer signal upon the transmitter transmitting the generated interrogation signal to the responder,

generates a stop timer signal upon the receiver receiving the response signal,

determines authenticity of the responder based on the received response signal and the random waveform of the generated interrogation signal, and

if the responder is determined to be authentic, determines identification of the responder using a time between the start timer signal and the stop timer signal, and the propagation times stored in the memory to find a corresponding responder identification.

10. An authenticity determination method, comprising:

storing a plurality of responder identifications and a plurality of predetermined propagation times in correspondence with each other;

generating an interrogation signal having a random waveform in an interrogation unit;

transmitting the interrogation signal from the interrogation unit to a responder;

generating a start timer signal upon transmitting the interrogation signal to the responder;

transmitting, upon receipt of the interrogation signal, a response signal from the responder to the interrogation unit;

generating a stop timer signal upon receipt of the response signal at the interrogation unit;

determining, in the interrogation unit, authenticity of the responder based on the response signal received from the responder and the random waveform of the generated interrogation signal; and

if the responder is determined to be authentic, determining identification of the responder by comparing a time between the start timer signal and the stop timer signal with the stored propagation times to find a corresponding responder identification.