
Accession Number : AD0687171
Title : NONPARAMETRIC LIKELIHOODRATIO DETECTION OF NOISELIKE SIGNALS,
Corporate Author : RESEARCH INST OF NATIONAL DEFENCE STOCKHOLM (SWEDEN)
Personal Author(s) : Gotherstrom,Lars
Report Date : 1969
Pagination or Media Count : 17
Abstract : The detection problem is solved in an almost optimum manner for signal and noise processes observed over a finite period of time. Signal and noise must show 'local' statistical stability and have finite second and fourth order moments. The observed variable is sampled at intervals that make the samples approximately chaindependent, thus reducing the dimensionality of the probabilitydensity functions (PDE) used. The detector operates as an adaptive likelihoodratio detector, where the zero hypothesis PDF is an average PDF. This average is taken over a number of direction sectors in a directionsensitive system, which reduces the possibility of adaptation under false hypothesis. The adaptive property consists of a repeated updating of the likelihood functions directly from the samples. The price of updating is decision delay. Tests with recorded noise and signals in the frequency band 100300 Hz have been made on a computer. Detector performance is shown as receiveroperating characteristics and as detector output as a function of time. This is done for various values of the signaltonoise ratio, the number of samples per decision, the number of direction sectors, etc. The likelihoodratio detector is also compared with a sampled squarelaw detector. The former is superior at low falsealarm probabilities, P sub fa < or = 0.01, even when the squarelaw detector operates at high sampling rates. (Author)
Descriptors : (*UNDERWATER SOUND SIGNALS, *DEMODULATION), NOISE, SAMPLING, PROBABILITY DENSITY FUNCTIONS, ADAPTIVE SYSTEMS, SWEDEN
Subject Categories : Cybernetics
Acoustics
Distribution Statement : APPROVED FOR PUBLIC RELEASE