DEMODULATION CIRCUIT FOR DIGITAL TV RECEIVING SYSTEM AND DEMODULATION METHOD THEREFOR

摘要

PURPOSE: A demodulation circuit for a digital TV receiving system and a demodulation method therefor are provided to perform frequency synchronization although a great frequency error exists by considerably adjusting an error of a receiving signal by a multi-path. CONSTITUTION: A PPF(PolyPhase Filter)(402) converts a digitalized IF(Intermediate Frequency) signal in response to an address selection signal to have a desired data rate, divides the converted signal into the first signal with a real component and the second signal with an imaginary component, and outputs the first signal and the second signal. A complex multiplier(403) multiplies the first signal and the second signal by a complex sine wave in which carrier is recovered, and generates the first and second baseband signals in which frequency offset is removed from the first signal and the second signal. A carrier recovering circuit(407) detects the frequency offset of the carrier from the first and second baseband signals, and generates the complex sine wave in proportion to the frequency offset. A matching filter unit(409) filters the first and second baseband signals, and controls an SNR(Signal to Noise Ratio). A sort circuit(413) shifts the frequency of the output of the matching filter unit(409). A DC removing circuit(415) adds outputs of the sort circuit(413), and removes a DC component from the added result. A sampling rate control circuit(423) changes the sampling rate of the output of the DC removing circuit(415), and outputs the changed sampling rate. A symbol timing recovering circuit(425) obtains a timing error of current symbols from the output of the DC removing circuit(415) in response to a carrier recovery signal, and generates the address selection signal corresponding to the timing error.