Data-Aided Carrier Tracking Loops

An innovation which improves the capability and performance of certain types of phase-coherent demodulators is introduced. This innovation has application in the fields of telemetry and tracking, e.g., relay satellite systems, deep-space communications, and military communication systems. The basic idea of the innovation centers around using the power in the composite signal sidebands to enhance the demodulator's effective signal-to-noise ratio (SNR). The vehicle through which this is accomplished employs the principle of decision-directed feedback. In its simplest form it is shown, for the first-order loop, that the maximum improvement in loop SNR relative to a standard phase-locked loop is 10 dB. The paper explores and illustrates the corresponding improvement realized in detection system efficiency. Extension to higher order loops follows directly from the analysis given here.