Simplified transversal correlator for MSK and MSK related waveforms

摘要

A transversal correlator is disclosed for demodulating a phase shift keyed (PSK) signal. The PSK signal is mixed with a local oscillator signal to produce quadrature I-channel and Q-channel signals. The I-channel and Q-channel signals are sampled at a periodic rate and the samples are propagated through a shift register for each channel. A preselected pseudo noise signal is stored in a local register which has an output tap for each stage. Each of the analog shift registers has a stage corresponding to one of the stages of the local register. Each of the I-channel and Q-channel samples is multiplied by the binary state in the corresponding stage of the local register. This multiplying operation produces a plurality of product signals. Product signals for alternate samples of the I-channel signal are summed with alternate but offset samples of the Q-channel signal to produce a first summation signal. The remaining alternate samples of the I-channel and Q-channel signals are also summed to produce a second summation signal. The first and second summation signals are full wave rectified then summed to produce a correlation output signal.