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A direct approach to the design of PM communications systems utilizing phase-locked demodulators is developed, and the design procedure is illustrated by example. In addition to the new design techniques, two other ideas are emphasized. First, the output signal-to-noise ratio (SNR) is defined as the ratio of the mean information power output to the total mean-square closed-loop phase error, which includes the effect of signal distortion on the design. Second, the safety margin is defined as the ratio of the total mean-square phase error diminished by the mean-square phase error due to signal distortion to the quantity representing the nominal or expected mean-square phase error due to additive noise. Although the design techniques developed in this paper are applicable for information waveforms having a flat power spectrum, a similar approach can be used for sine-wave modulation. The equations representing the output SNR for sine-wave modulation are included. An experimental PM communications system has been constructed, and the results of initial tests show good agreement with the predicted performance.
Space Electronics and Telemetry, IRE Transactions on (Volume:SET-8 , Issue: 2 )
Date of Publication: June 1962