A theoretical and experimental comparison of output signal-to-noise ratios of three types of cross correlators

The output signal-to-noise ratio as a function of input signal-to-noise ratios is compared for three different types of cross-correlators: 1) the standard analog cross correlator consisting of bandpass filters, multiplier, and low-pass filter; 2) the polarity coincidence correlator (PCC) which incorporates hard limiters in each analog input channel; and 3) a modified type of PCC wherein only one of the analog channels utilizes a hard limiter. Some of the previous theoretical work on the PCC is extended to include new expressions for the output signal-to-noise ratio from which computations can more readily be made. In addition, discrete circuits were fabricated that closely approximate idealized elements so as to experimentally verify the theoretical results. In almost all cases tested, the experimental results were in close agreement with the math models.