Beamforming: Performance analysis and underwater acoustic signal processing.

Abstract

The first part of this thesis explores the performance of the adaptive beamformer in the pseudo-noise signal systems. We consider a receiver consisting of an adaptive beamformer and matched filter. The purpose of this study is to find how the order of processing affect the adaptive beamforming performance and the receiver performance under finite observations. The asymptotic assumption for adaptive beamformer is removed by the computation of the Bayes-optimal beamformer performance under finite observations. The results of Monte Carlo simulation indicate that the system where matched filtering precedes adaptive beamforming has lower signal-to-noise ratio threshold. In the second part of the study, the measured data from the Greenland Sea MST'88 experiment were processed to construct a picture of the ownship noise and the multipath transmission structure of the ocean acoustic channel in the experiment. Our study shows that the ownship noise can be treated as a single broadband plane wave in array processing. In processing the signal arrival, a sub-optimal method is introduced to suppress the inter-code interference when the transmissions from different sources are overlapped at the receiver. The processing for multipath identification is also discussed.