Demodulator, modulation and demodulation system, and demodulation method

摘要

A demodulator of the present invention comprises a clock signal generator for generating a clock signal having a frequency that is 4 times n times (n is an integer greater than zero) the carrier frequency of a received signal, an analog-to-digital (A/D) converter for converting the received signal into a digital signal, a complex signal generator clocked by the clock signal to generate a complex signal comprised of the received signal as a real part and a pi /2 phase-shifted signal as an imaginary part, a phase rotator for generating quasi-coherent detected signals by multiplying the complex signal by specific values of the carrier frequency, and a decimation circuit clocked by a clock signal to generate the required I channel signal and Q channel signal by decimating the quasi-coherent detected signals so as to finally obtain improved accuracy for accomplishing quadrature detection and eliminate an amplitude deviation and a direct-current offset.