公开(公告)号：JP2001266102A

公开(公告)日：2001-09-28

申请号：JP2001026126

申请日：2001-02-01

Applicant: ST MICROELECTRONICS SA

Inventor： ROBERTS ANDREW J ,  SUBBIOTTO FREDERIC

IPC: G06K7/08 ,  G06K19/07 ,  H03D1/10 ,  H04B1/59 ,  H04B5/02 ,  H04L25/06 ,  H04L27/06 ,  H04L27/08

Abstract: PROBLEM TO BE SOLVED: To provide a demodulator for non-contact chip card, which is not affected by the level of a received signal. SOLUTION: A non-contact chip card where binary data is transmitted by a radio frequency includes a demodulator for binary data. The demodulator includes a circuit for detecting a transmitted signal, a rectifying circuit, a band pass filter, a comparator stage and a memory circuit. The band pass filter gives a low frequency signal used as a reference for two comparators and a high frequency signal supplied for comparison with the reference which changes with the low frequency signal. Consequently, demodulation is not affected by the average level of the received signal.