| 摘要 |
PROBLEM TO BE SOLVED: To provide a digital modulation signal demodulator capable of attaining demodulation at a low error rate by reducing a frequency error at demodulation with respect to a modulation signal of a PSK system and decreasing the effect of Gaussian noise. SOLUTION: An A-D converter 21 samples an analog input signal s(t) to convert the sampled signal into a digital value, a pre-processing section 22 applies amplitude stabilization and noise suppression processing to the digital value, and the resulting digital value is given to an quadrature demodulator 32. The quadrature demodulator 32 multiplies a digital value sequence S' with biphase local signals L1, L2 from a local signal generator 31, respectively, to extract baseband signals I', Q' on the basis of a result of the multiplication. An error detection means 33 detects a phase error caused by a difference between a carrier frequency of the input signal and frequencies of the local signals on the basis of the baseband signals I', Q', and a local signal control means 34 controls the local signals so as to decrease the detected phase error. The data demodulator 35 detects phase information from the baseband signals I', Q' in a state that the phase error is compensated to demodulate data. COPYRIGHT: (C)2007,JPO&INPIT
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