IMPULSE RESPONSE MEASUREMENTS WITH AN OFF-LINE CROSS CORRELATOR

The impulse responses of simulated systems have been computed by off- line cross-correlation of the system input and output signals. The input test signal consisted of a discrete interval binary code whose autocorrelation was a triangular pulse at zero lag. The main object of the experiments was to study the inaccuracies introduced in ideal, noise-free systems by determining the impulse response digitally from sampled versions of the system input and output signals. A second object was to determine the error introduced by adding controlled amounts of uncorrelated noise at the system outputs. The experimental results showed that for signal-to-noise ratios greater than 10 : 1 in the mean square sense, the impulse responses may be determined with reasonable accuracy using only one cycle of the binary code. The method lends itself to online computation of system impulse responses. The latter could be used to monitor the stability of the system or to determine control parameters in an adaptive control system. (auth)