Fast envelope correlation for passive ranging.

Abstract

Application of classic triangulation methods will allow the location of a radar to be determined by passive sensors. Through the use of modern digital signal processing techniques this estimate can be made in a simpler fashion using a conventional receiver. In this thesis a technique is developed for time difference of arrival (TDOA) estimation using a frequency domain based correlation detector driven by an envelope detector. Time lag boundaries are defined on the output of the correlator. A fixed detection threshold is calculated to permit constant false alarm rate (CFAR) detection. The performance of the correlation detector is plotted as a receiver operating characteristic (ROC) curve as a function of signal to noise ratio (SNR) . An interactive MATLAB software program is provided to perform either spectral domain or time domain based correlation. Spectral domain based correlation uses the Fast Fourier Transform (FFT) . Implicit with the use of the FFT are finite arithmetic internal processing errors which are modeled as independent uncorrelated noise sources. A method is presented to account for SNR degradation at the output of the FFT.