Accession Number : AD0477195


Title :   ARRAY GAINS FOR BEAMFORMERS OPERATING WITH A MULTIMODAL MEDIUM AND A PARTIALLY DIRECTIVE NOISE FIELD,


Corporate Author : COLUMBIA UNIV DOBBS FERRY NY HUDSON LABS


Personal Author(s) : Williams, Ross E


Report Date : Nov 1965


Pagination or Media Count : 29


Abstract : Formulas are derived for the processing gain of a multi-element receiving array operating in a non-isotropic noise field and in a medium that supports multipath signal arrivals. In particular, it is assumed that the noise field consists of an isotropic part plus a superimposed field produced by distant discrete noise sources. Derivations are made without restricting the nature of the multipath arrivals, but the tabulated examples refer to cases in which the signal and noise bandwidths are sufficiently broad that only a few arrivals overlap in a time comparable to the main lobe width of the signal and noise autocorrelations, and to cases for which the receiving array is sufficiently dispersed to allow only a few arrivals to be angularly unresolved. The computations are made for an array which sums the analog signals for all individual receivers, and for one which sums the hard-clipped versions of these signals. Despite the restriction in the examples to only a few arrivals overlapping in time and angle, the effects of multipath interference, multipath normalization (for the hard-clipped array) and a few discrete noise sources cause the resultant signal-to-noise enhancement for the array to differ markedly from the (10 log N) dB result characteristic of a single arrival and an isotropic, uncorrelated noise field. (Author)


Descriptors :   *SONAR RECEIVERS , PERFORMANCE(ENGINEERING) , GAIN , UNDERWATER SOUND SIGNALS , UNDERWATER SOUND , SOUND TRANSMISSION , SONAR , SONAR EQUIPMENT , HYDROPHONES , ELECTROACOUSTIC TRANSDUCERS , MULTIPATH TRANSMISSION , NOISE , DATA PROCESSING , ANALOG SYSTEMS , MATHEMATICAL ANALYSIS , SIGNAL TO NOISE RATIO , DIGITAL SYSTEMS


Subject Categories : Acoustic Detection and Detectors


Distribution Statement : APPROVED FOR PUBLIC RELEASE