Patent ID: 7961077

Claim:
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.