| 摘要 |
PROBLEM TO BE SOLVED: To provide a frequency selection circuit and a demodulation circuit which are superior in signal selectivity with simple circuit configurations. SOLUTION: The demodulation circuit includes: a sampling circuit 1 for sampling a high frequency signal including a signal modulated with a carrier signal of a prescribed frequency, by a frequency being an integral multiple of the frequency of the carrier signal; and a comparator 2 for generating a binary demodulation signal in accordance with whether the output amplitude of the sampling circuit 1 exceeds a prescribed reference amplitude or not. The sampling circuit 1 includes: a resonator 3 and a negative resistance circuit 4 connected to each other; a control circuit 5 for controlling the negative resistance value of the negative resistance circuit 4; a plurality of switches SW1 to SW5; a differential amplifier 6; and a capacitor C1. Frequency selection performance of very high Q is obtained by connecting the negative resistance circuit 4 to the resonator 3, and only a desired frequency component included in a high frequency signal is precisely extracted and subjected to demodulation processing. COPYRIGHT: (C)2006,JPO&NCIPI
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