Patent ID: 7932775

Claim:
A digital demodulation device for demodulating an amplitude modulation (AM) signal whose carrier has a first frequency, the digital demodulation device comprising: a processing circuit for performing first path digital processing and second path digital processing according to a second frequency and a plurality of digital values of the AM signal, wherein the first path digital processing represents performing down conversion by mixing the AM signal with a first sinusoidal signal whose frequency is equal to the second frequency, the second path digital processing represents performing down conversion by mixing the AM signal with a second sinusoidal signal whose frequency is equal to the second frequency, the second frequency is equal to the first frequency plus a predetermined frequency shift, and the second sinusoidal signal is orthogonal to the first sinusoidal signal; and an output stage, coupled to the processing circuit, for outputting an output signal according to first processing results of the first path digital processing and second processing results of the second path digital processing; wherein the predetermined frequency shift is not less than an upper bond frequency of a sensitive range of human hearing or a cut-off frequency of a latter stage of the output stage, so that a noise component corresponding to the predetermined frequency shift in the output signal is capable of being reduced or removed.