Research On Passive Synthetic Aperture In The Signal Detection Of The Line Array

The technique of passive synthetic aperture is of great interests for underwater acoustic community in the world. Because of its unique characteristic of high spatial gain and high azimuth resolution, it will certainly be used extensively in civilian and military fields. When passive synthetic aperture technique is applied to linear array, we can achieve a longer dummy array which is several or several decade times of conventional real aperture linear array. By exchanging time gain with spatial gain, passive synthetic aperture processing makes use of delay compensation to obtain higher dynamic spatial gain, and extremely improve detecting performance of weak signal.Great effort has been made to put passive synthetic aperture technique into underwater acoustic field abroad, and they have made some achievement in building theoretical model, simulation analysis and experimental research. In our country, however, the research work on passive synthetic aperture sonar is only a start and we have a lot of work to do in this field.Base on research on applying passive synthetic aperture technique to linear array, this paper shows the principle of the passive synthetic aperture and builds its mathematical model. Several methods for passive synthetic aperture technique applied for signal detecting are analyzed and compared; also application to passive ranging is discussed preliminarily. For simulation research, comparing with conventional beamforming, result processed by FFTSA(FFT Synthetic Aperture ) algorithm which is one of passive synthetic aperture techniques distinctly improve dynamic spatial gain and azimuth resolution, enhancing detecting performance of weak signal. When passive synthetic aperture technique is applied to passive ranging, it increases the real aperture array length and increases the SNR(Signal Noise Ratio), simulation result has prove that it improves passive ranging precision.