Theory and measurement of sampling and coarse quatization effects in a signal memory

Abstract

The effects of sampling and coarse quantisation on signal fidelity at the output of a Digital Radio Frequency Memory (DRFM) memory module have been considered. Fourier analysis on deterministic signals after quantisation and sampling has been contrasted and compared to the generalised statistical appzoaoh of randomly distributed quantisation errors within the quantising intervals. It has been shown theoretically and by measurement, that the spectra of coarsely quantised signals contain quantisat:i.on noLsa that is coloured, as oppos ed ,to whi t:e, especially if the sample correlation coefficients are high. Coarse quantisation produces spurs (harmonics) that appear in the message band eithe): as aliasec1. or unaJ.iased spurs. Harmonic power summation yielded quant.Lsat.Lcn noise powers that correlated \llel1 with the generalised approach from three bits of quant.LaabLon upwards, and near identical results for six bits. Spectral measurements were made on a one bit quantiser and the results obtained compared favourably with the theoreticCil pzedLc'' tons, showing the harmohic spurs and the effect of spectral fold-over.