| 摘要 |
PROBLEM TO BE SOLVED: To provide an ASK demodulation circuit of a collation terminal which can obtain a demodulation output constantly including such a case as a transmission/reception phase difference becomes 180°. SOLUTION: First and second quadrature demodulators 310 and 330 are employed. The first quadrature demodulator 310 has a first demodulator 311 and a second demodulator 312, and the second demodulator 330 has a third demodulator 331 and a fourth demodulator 332. The first demodulator demodulates ASK acknowledge by a local oscillation signal of a reference phase, the second demodulator demodulates the ASK acknowledge by a local oscillation signal having a phase shift of 90°from a reference phase, the third demodulator demodulates the ASK acknowledge by a local oscillation signal having a phase shift of 180°from the reference phase, and the fourth demodulator demodulates the ASK acknowledge by a local oscillation signal having a phase shift of 270°from the reference phase. COPYRIGHT: (C)2006,JPO&NCIPI
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