| 摘要 |
PROBLEM TO BE SOLVED: To provide a FSK receiving device which can generate a recovery signal with sufficient accuracy at low cost, even when a modulation index is low. SOLUTION: A frequency conversion circuit converts a high frequency signal transmitted by carrying out frequency shift modulation into an intermediate frequency signal of a predetermined frequency and outputs it. An amplitude limiting circuit restricts and outputs the amplitude of an output signal of a frequency conversion circuit. The first signal generation circuit of a orthogonal demodulation circuit generates a pair of first local oscillation signals whose mutual phases intersect. Both frequencies of the first local oscillation signal are k times (k:3 or more odd number) a predetermined frequency. The I side mixer of the orthogonal demodulation circuit mixes the output signal of the amplitude limiting circuit and one side of the first local oscillation signal, and outputs it. The Q side mixer of the orthogonal demodulation circuit mixes the output signal of the amplitude limiting circuit and another side of the first local oscillation signal, and outputs it. The orthogonal demodulation circuit generates a demodulated signal based on the output signal of the I side and the Q side mixers. COPYRIGHT: (C)2006,JPO&NCIPI
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