Patent ID: 6868131
Filing Date: 2005-03-15
Classification: H04H,H04L

Abstract:
1. A demodulation apparatus for demodulating modulated signals, the apparatus comprising: a digital signal generator for performing synchronous detection of a modulated input signal and for making an A/D conversion to generate digital signals corresponding to phase axes; a frequency correction value outputting unit for outputting a frequency correction value set on the basis of a symbol rate; a frequency corrector for giving a frequency offset to the digital signals on the basis of the frequency correction value to generate frequency-corrected signals; a timing recovering unit for performing timing recovery by extracting symbol timing for the frequency-corrected signals; a C/N detector for detecting C/N from a symbol obtained by the timing recovering unit; an optimum frequency correction value determining unit for treating a frequency correction value corresponding to the maximum value of the C/N as an optimum frequency correction value; a carrier recovering unit for performing carrier recovery by correcting finally a shift in the frequency of a signal on which a frequency correction by the use of the optimum frequency correction value and timing recovery have been made; and a synchronization detector for making an error correction on a symbol after carrier recovery and for detecting a unique word.