Robust Deconvolution of Correlation Functions

A new generalized cross-correlator (GCC) is presented which can provide greatly improved resolution in delay estimation measurements. Generalized crosscorrelation is a technique in which the input signals are prefiltered, in some optimal manner, before crosscorrelating. The prefilters for this GCC are robust (in the minimax sense) linear filters which have found use in linear equalization. The presence of the prefilters, in effect, deconvolves the cross-correlation function. An example of the use of this new GCC is provided by locating acoustic emissions from partial discharge in a high voltage, solid cast transformer. Partial discharge is an electrical phenomena caused by defects in the insulation systems of transformers and is observed as both electrical and acoustic emissions. Time delay estimation techniques used to locate the emissions sites in power transformers are complicated by the multipath signals that are present. Experimental measurements of the acoustic emissions are used to illustrate the effectiveness of this new GCC in combating the problems associated with multipath signals.