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在全数字化QPSK解调器中,有时存在着相当大的相对载波频偏,导致接收机不能正常工作。针对QPSK信号相干解调中载波同步问题,提出一种采用FFT及锁相环联合提取大频偏信号载波的方法,达到了对大频偏进行有效估计并提取较纯载波的目的。该方法统计性能好,结构简单,可估计的载波频率适应范围大,算法适合数字电路实现。
In fully digitized QPSK demodulators, there are sometimes significant relative carrier frequency offsets that cause the receiver to not function properly. Aiming at the problem of carrier synchronization in QPSK signal coherent demodulation, a method of combining FFT and phase-locked loop to extract carrier with large frequency offset is proposed, which can effectively estimate large frequency offset and extract pure carrier. The method has the advantages of good statistical performance, simple structure, large estimated range of carrier frequency adaptability, and the algorithm suitable for digital circuit implementation.