Patent ID: 7109844

Claim:
A transponder for use in a communication system including, in addition to the transponder, an interrogator which transmits a carrier wave to the transponder so that the transponder receives the carrier wave, modulates the received carrier wave, and returns the modulated carrier wave as a reflected wave to the interrogator, the transponder comprising: a carrier wave receiving and returning device which receives and returns the carrier wave transmitted from the interrogator; a frequency hopping device which hops a frequency of a subcarrier wave according to a frequency hopping pattern representing a unit data as a first portion of an information signal, and thereby modifies the subcarrier wave; and a carrier wave modulator which modulates, based on the subcarrier wave modified by the frequency hopping device, the carrier wave received by the carrier wave receiving and returning device, so that the carrier wave receiving and returning device returns the modulated carrier wave as the reflected wave to the interrogator.