A NEW PASSIVE SYNTHETIC APERTURE TECHNIQUE FOR TOWED ARRAYS

Various synthetic aperture techniques have been investigated in the past to increase signal gain and improve angular resolution for towed line array systems. A new algorithm is presented here that synthesizes apertures in the beam domain using FFT transformations and performs coherent processing of subaperture signals at successive time intervals. Experimental tests of the new algorithm show that for ocean environments with spatial coherence longer than the synthetic aperture length and for signals with temporal coherence longer than the required acquisition time, a synthetic array gain is achieved which roughly corresponds to the length of an equivalent fully populated array, and it is consistent with Yen and Carey's experimental observations [2]. In the experiments, transducer generated CW with phase stability and pseudorandom signals were used. Limitations on the spatial and temporal coherence were introduced only by the medium, the temporal coherence of the pseudorandom signal, and the shape and stability of the line array used.