The Action of Dither in a Polarity Coincidence Correlator

An analysis has been made of how dither added to the input of a polarity coincidence correlator eliminates capture of a weak signal by an unwanted signal. For certain interfering environments the output signal-to-noise ratio of various correlators with three specific input dithers is analyzed. The correlators considered were a polarity coincidence correlator with: 1) no dither, 2) dither of random, amplitude uniformly distributed between the chosen plus-and-minus peak values, 3) sinusoidal dither, and 4) Gaussian dither. Each correlator was analyzed for the cases of Gaussian-noise, rectangular-wave, and sinusoidal interference and compared with the classical correlator. The choice of dither amplitude based upon the measured value of the noise power was studied. A uniformly distributed dither is shown to be slightly superior to sinusoidal dither, and both superior to Gaussian noise.