| 摘要 |
In order to coherently demodulate an incoming multi-phase PSK analog signal irrespective of large frequency deviation, an automatic frequency feedback loop is provided. An analog baseband signal is generated by multiplying the IF analog signal by a local signal and then is converted into the corresponding digital baseband signal. A multiplier multiplies the digital baseband signal by another local signal. The output of the multiplier is further multiplied and then applied to a plurality of single-tuned filters which are arranged in parallel and have tuning frequencies each different from an adjacent frequency by a predetermined frequency interval. Each of the plurality of single-tuned filters generates a signal for use in carrier recovery, a frequency error signal and a correlation coefficient. Subsequently, one of the plurality of single-tuned filters is selected in a manner wherein the maximum value is detected among the correlation coefficients. The another local signal is generated using the frequency error signal of the single-tuned filter which has been selected. A modulating signal is reproduced using the recovered carrier in a conventional manner. <IMAGE> |
