Circuit for Approximate Computation of Reciprocal of Time Delay to Maximum Cross Correlation

A circuit was developed to measure the inverse time delay to maximum cross correlation between two stationary time varying voltages. The first voltage is delayed in a sample-and-hold circuit whose sampling frequency is swept. When the delay between the two signals is smaller than a quarter of the period of the fundamental, the sample-and-hold voltage is directly multiplied with the downstream voltage. When the delay is greater than a quarter of the period of the fundamental, the sample-and-hold signal is multiplied by the sample-and-hold value of the second signal, sampled at the same rate, 180° later. The filtered product for both cases has a maximum when the sampling frequency is inversely proportional to twice the delay to maximum cross correlation.