Performance of QPSK coherent detection with dual-mode carrier recovery circuit for fast and stable carrier tracking

A new type of carrier recovery circuit suitable for coherent detection in digital land mobile radio transmission is studied experimentally. The authors propose a dual-mode carrier recovery (DCR) circuit which adaptively selects one of its two operation modes: the conventional mode or the adaptive carrier-tracking (ACT) mode. The ACT mode controls the reference phase digitally, and enables instantaneous phase tracking in burst signal operation and/or in a fast fading environment. The DCR coherent demodulator performance is identical to that of conventional coherent detection in the low CNR region, and to that of differential detection in the high CNR region where the ACT mode is selected