Fast carrier-tracking coherent detection with dual-mode carrier recovery circuit for digital land mobile radio transmission

摘要

A new type of carrier recovery circuit suitable for coherent detection in digital land-mobile radio transmission is studied experimentally. A dual-mode carrier recovery (DCR) circuit is proposed that adaptively selects one of two phase locked-loop operation modes: the conventional mode or the adaptive carrier-tracking (ACT) mode. The ACT mode digitally controls the reference phase, 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.