Transponder, interrogator, and communication system

An interrogator for use in a communication system including, in addition to the interrogator, a transponder, the interrogator transmitting a carrier wave to the transponder so that the transponder receives the carrier wave, modulates the received carrier wave based on a subcarrier wave modified according to a frequency hopping pattern, and returns the modulated carrier wave as a reflected wave to the interrogator, the interrogator comprising:

• a carrier wave transmitter which transmits the carrier wave to the transponder;
• a reflected wave receiver which receives, as the reflected wave returned from the transponder, the carrier wave modulated based on the subcarrier wave modified according to the frequency hopping pattern;
• a demodulator which demodulates the reflected wave received by the reflected wave receiver, into a demodulated signal;
• a frame-data obtaining device which obtains, from the demodulated signal, at least one frame data;
• a frequency hopping pattern recognizer which recognizes, from the demodulated signal, the frequency hopping pattern;
• and
• an information obtaining device which obtains, from said at least one frame data obtained by the frame-data obtaining device and the frequency hopping pattern recognized by the frequency hopping pattern recognizer, identification information usable to identify the transponder, and transmission information transmitted with the identification information from the transponder to the interrogator.

A communication system, comprising:

• at least one interrogator;
• and
• at least one transponder,
• said at least one interrogator including
• a carrier wave transmitter which transmits a carrier wave to said at least one transponder,
• a reflected wave receiver which receives, as a reflected wave returned from said at least one transponder, the carrier wave modulated based on a subcarrier wave modified according to a frequency hopping pattern,
• a demodulator which demodulates the reflected wave received by the reflected wave receiver, into a demodulated signal,
• a frame-data obtaining device which obtains, from the demodulated signal, at least one frame data,
• a frequency hopping pattern recognizer which recognizes, from the demodulated signal, the frequency hopping pattern, and
• an information obtaining device which obtains, from said at least one frame data obtained by the frame-data obtaining device and the frequency hopping pattern recognized by the frequency hopping pattern recognizer, identification information usable to identify said at least one transponder, and transmission information transmitted with the identification information from said at least one transponder to said at least one interrogator,
• said at least one transponder including
• 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 the subcarrier wave according to the frequency hopping pattern representing a unit data as a portion of an information signal representing the identification information and the transmission information, 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 said at least one interrogator.