PERFORMANCE OF A QUADRICORRELATOR DRIVEN BY MODULATED SIGNALS

This paper presents an analysis of a balanced quadricorrelator driven by a digital-modulated signal plus thermal noise. The aim is to assess its performance as a frequency different detector. The circuit output is decomposed into a signal term and a disturbance referred to as noise. Expressions are given for the signal and for the power spectral density of the noise as a function of the various system parameters. Design criteria are provided to minimize the output noise for zero frequency offset. In particular it is found that at high signal-to-noise ratios the noise level can be made vanishing small by proper choice of the quadricorrelator filters. A similar result has been recently discovered for another frequency difference detector, the dual-filter detector. It is shown that a balanced quadricorrelator and a dual-filter detector can be made totally equivalent.