To enable an interrogator to receive data of a response wave returned from a responder at the same time with writing data of a writing wave to the responder regarding a communication method in a transponder.
This transponder is provided with the interrogator Q which has a transmitting function for transmitting the writing wave S1 and an interrogation wave S2 and a receiving function for receiving the returned response wave S3, and with the responder R which receives the writing wave S1 transmitted from the interrogator Q to write data, receives the interrogation wave S2 to read response data and to apply diffusion modulation and returns the resultant response data as the response wave S3 to the interrogator Q. In the transponder, the transmitting function of the interrogator Q simultaneously transmits the writing wave S1 and the interrogation wave S2 subjected to the same modulation to the responder R, and a means for negating modulation components of the transmitted interrogation wave S2 about data of the response wave S3 received by the interrogator Q is provided between the transmitting function side and the receiving function side of the interrogator Q.
UJIIE TAKESHI
KOBAYASHI TAKAYUKI
YAMAMOTO MASANORI
