The phase locked loop circuitry locks on the arriving carrier wave and estimates its phase.

The frequency difference between the center of the spectral main lobe and the first zero crossing is called as the minimum required spacing in non coherent detection.

Coherent detector considers phase as the most important parameter. This coherent detector is also known as maximum likelihood detector.

DPSK has twice as much as noise than in PSK. The error probability in DPSK is twice (3db) worse than PSK.

In non coherent detection the minimum tone separation corresponds to 1/T.

The input signal comprises of a prototype signal plus noise and the bandwidth is 1/2T where T is the symbol time and minimum nyquist sampling rate can be given as 2W or 1/T.

Matched filter is used for coherent detection. It cannot be used for non coherent detection because matched filter output is a function of unknown angle α.

In differential encoding, the phase of the present signal waveform is compared with the phase of the previous signal.

In this method, the data is encode deferentially that is the presence of binary zero or one is manifested by symbol’s similarity or difference when compared to that of the previous symbol.

An envelope detector consists of a rectifier and a low pass filter. The detectors are matched to the envelopes and not to the signal themselves.