| 摘要 |
Non contact card reader (10) has at least two antenna (11,12) and an antenna modulation circuit having: (a) first modulation mode in which antenna modulations are subject to constructive interference moving away from reader, and; second modulation mode in which antenna modulation is destructive moving away from reader. Modulation is two state modulation. Antennas are modulated in two distinct states in the first mode and in the same state in the second mode. Modulation is either phase or amplitude. both the antennas are identical coplanar or plane devices. An integrated circuit card (13), for non contact reading, includes at least two antennas (14,15) and an antenna demodulation circuit which: (a) sums the demodulated signals from each of the antennas in a first demodulation mode, and (b) finds the difference of the demodulated signals in a second demodulation mode. The demodulation circuit includes for each antenna (14,15) an amplitude, preferably a diode (34,35), or a phase demodulator. The antennas are identical.
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