| 摘要 |
A demodulation apparatus of digital detection processing type of the invention offers versatility as consumer equipment in mobile communications, ATV, satellite broadcasting, CATV, and the like. A modulated wave output is obtained by multiplying an input digitally modulated wave signal by a local oscillating signal from a local oscillator. The obtained modulated wave output has a center frequency which is substantially equal to the symbol frequency. The modulated wave output is A/D converted at a rate which is four times as high as the symbol frequency, so as to be output as interleaved I and Q digital data. The I and Q data is split, and the split I and Q data are multiplied by coefficients of "+1" and "-1", respectively. The multiplied two output signals are selectively output. Thus, the data multiplied by the coefficients of "+1" and "-1" are alternately output for the I and Q signals, so as to perform the digital detection. The processed I and Q data are subjected to digital channel filter processing for spectrum shaping/An interpolation signal for one of the output signals of digital channel filters is generated and output. An amplitude level value of the interpolation signal is controlled, and then the timing of the interpolation signal is matched with the timing of the other one of the output signals of the digital channel filters. The phase error detection and the waveform shaping are performed for the I and Q data having the matched timings, and the data identification is performed.
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