Accession Number : ADA184258

Title :   Lower Bounds on Bearing Accuracy for Closely Spaced Sources.

Descriptive Note : Final rept.,

Corporate Author : AMERICAN SOCIETY FOR ENGINEERING EDUCATION WASHINGTON DC

Personal Author(s) : Hamilton, Miriam

PDF Url : ADA184258

Report Date : 01 Sep 1987

Pagination or Media Count : 75

Abstract : This report presents Cramer-Rao lower bounds on bearing estimation error for two closely spaced incoherent sources which radiate spectrally overlapping broadband Gaussian noise. The radiated signals are assumed to occupy the same frequency band which is taken to be lowpass and rectangular in shape. In the most general problem setting, when prior knowledge of signal levels or a single source bearing is unavailable, estimation accuracy is shown to degrade in proportion to the second power of the inverse angular spacing, resulting in large degradations when compared to the accuracy attainable in a single source setting. There is evidence that in certain situations, a form of apriori knowledge concerning signal power levels can be used to significant advantage in joint bearing estimation. Detectability of a second source from signal field containing two closely spaced sources that overlap in both time and frequency depends on the resolving power of the array and is expected to be poor at low signal-to-noise ratios and short observation times when the angular spacing is small. Results of a binary hypothesis test indicate that below a well defined threshold the probability of error in guessing the wrong hypothesis tends to one half. Reachability of the earlier computed Cramer-Rao lower bounds for this regime is questionable.

Descriptors :   *BEARING(DIRECTION), *SONAR SOUND ANALYZERS, ACCURACY, BINARY SYSTEMS, HYPOTHESES, ESTIMATES, ERRORS, BROADBAND, GAUSSIAN NOISE, FREQUENCY BANDS, INVERSION, DEGRADATION, RADIATED NOISE, SIGNAL TO NOISE RATIO, MAXIMUM LIKELIHODD ESTIMATION, LOW LEVEL, SHORT RANGE(TIME), INCOHERENT SCATTERING, OVERLAP, PROBABILITY, POWER LEVELS, SETTING(ADJUSTING)

Subject Categories : Acoustic Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE