ANTENNA CIRCUIT FOR READER/WRITER

摘要

PROBLEM TO BE SOLVED: To allow a reader/writer to surely read a return signal by suppressing a signal of a waiting time to receive at a detection terminal of a receiver even when the return signal from a card is weak in the reader/writer of a noncontact data carrier system consisting of the reader/writer and the passive card. SOLUTION: An antenna circuit 2 for reader/writer in a noncontact data carrier system consisting of a reader/writer RW and a passive card CD is provided with a 1st voltage generating means that generates a voltage, proportional to strength of a transmission signal to the card CD and a 2nd voltage-generating means that generates a cancellation voltage of a reverse polarity to that of the voltage generated from the 1st voltage generating means, so that the cancellation voltage is supplied to a receiver 3.