Automatic recognition of phase keyed signals - storing differences between consecutive phases from digital channel filters in form of histogram from which various parameters are derived

摘要

The received phase keyed signal is complex demodulated and digitalised, and the complex base band signal components are filtered through digital channel filters with different bandwidths but the same centre frequency signal amplitude and phase is measured for each channel. The clock pulse times at which the amplitudes are measured and instantaneous phases determined are obtained from the amplitude values of their square by narrow band filtering. The differences between two consecutive phases in each channel are stored in the form of a histogram, from which the phase keying, the number of phase states, receiver tuning conditions and the approx. cycle rate in real time are recognized. These parameters are determined by cross-modulation with modulation matched reference functions and testing the amplitude of the filtered out clock signal.