NONCONTACT IC CARD SYSTEM, CARD READER FOR IC CARD, AND IC CARD

摘要

PROBLEM TO BE SOLVED: To accurately transmit data without being affected by a noise electric field around an antenna by varying the load on the transmission system between an IC card and a card reader and allowing the card reader to detect a reflected wave on the transmission system according to the load state and specifying the transmit data according to the reflected wave. SOLUTION: The switching circuit 10 on the IC card side varies the AC characteristics of the IC card side according to the transmit data from the IC card. Consequently, the load on the transmission system varies and a reflected wave corresponding to its extent is generated. The reflected wave detecting circuit 4 provided on the card reader side detects the reflected wave generated on the transmission system according to the variation in the load state of the transmission system. Then the data specifying circuit 15 in a control circuit 2 compares pulse data obtained corresponding to the detected reflected wave with a threshold value and performs a data parallelizing processing to specify the transmit data. The intensity of the reflected wave generated on the transmission system depends upon the load on the transmission system and is not affected by the noise electric field around the antenna.