The Detection of Nonfluctuating Targets in Log-Normal Clutter

摘要

Measurements of sea clutter using high-resolution radar indicate that the clutter-cross-section returns follow a log-normal probability density function more closely than the usually assumed Rayleigh law. This report develops the theory for the detection of a steady signal in log-normal clutter by first using a single pulse and then by using the sum of N pulses integrated noncoherently. Plots of the probability density of the envelope of the signal plus clutter show the function to be bimodal, an unexpected result. Curves are presented for the threshold bias, normalized to the median clutter voltage, versus the probability of false alarm for several values of the standard deviation sigma and for various values of N. Probability of detection curves are presented for sigma = 3, 6, and 9 dB, for N = 1, 3, 10, and 30 pulses, and for false alarm probabilities from 0.01 to 10 to the minus 8th power. The ratio of signal to median clutter required for detection increases markedly as sigma increases because of the highly skewed clutter density. (Author)