Effective Threshold Time Delay Estimation in the Presence of Interference and Noise

This chapter examines the statistical effect of a strong spectral peak on the time delay estimates by the generalized correlator when the wideband source and the sinusoidal source are or are not collocated. It also includes simulation results for all windows, from which are deduced histograms of the time delay estimate, probability of the time delay falling within a selected gate P_G, and mean and variance of the time delay estimate. At signal-to-noise (S/N) ratios near threshold, the correlation output is corrupted by false peaks. In practice, the large global errors are avoided by the use of a gate centered about the expected time delay. The results quantify the accrued improvement due to proper windowing for S/N ratio near threshold. The chapter emphasizes the importance of proper gating of the time delay estimate in combination with windowing of the cross-spectrum.