Polarity coincidence correlation detection of a weak noise source

Abstract

One application of sample polarity coincidence correlation to the detection of a weak noise source in background noise is briefly described. Assuming an input SNR much less than one, and Gaussian input signals and noise with identical normalized power spectra, expressions for the output SNR are derived for the analog and the polarity coincidence correlator, with and without sampling. The loss in attainable SNR due to clipping and sampling is computed for three different input spectra, viz.; white noise which is passed through an RC low-pass filter, a single-tuned band-pass filter or a rectangular filter. The resulting loss is given in three diagrams, as a function of relative bandwidth of the input signal and sampling frequency. For broad-band input signals the loss is between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</tex> db, and between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</tex> db for narrow-band signals.