Convolution and correlation by nonlinear interaction in a diode-coupled tapped delay line

Abstract

A new type of nonlinear delay‐line correlator is described which makes use of a tapped piezoelectric surface‐acoustic‐wave delay line and a series chain of forward‐biased semiconductor diodes. Nonlinear signal mixing in the diode chain is utilized to perform serial product convolution or correlation of arbitrary signal modulation applied at two input ports. Because of the large nonlinearity available with semiconductor diodes, insertion loss for the new correlator is relatively low, approximately 25 dB for the initial experiments reported here. Convolution and correlation experiments are described for an eight‐tap correlator operating with input and mixing frequencies in the 30‐ to 60‐MHz range.