Improving arrays for multi-angle swath bathymetry

Multi-angle swath bathymetry sonar systems use the range and estimates of the angle of signal arrival to determine bottom depth. The accuracy of angle of arrival estimates is influenced by a number of factors including noise levels, the presence of multipath arrivals, signal bandwidth, pulse length etc. Angle estimation accuracy is also affected by the integrity of the transducer array employed to receive the returning signals. This paper addresses some of the issues associated with transducer design for multi-angle swath bathymetry systems including inter-element crosstalk and housing interactions. Beampatterns and relative angle responses are presented for transducer arrays that show evidence of crosstalk and housing interactions. It is shown that the crosstalk and housing interactions can be reduced through the use of different inter-element materials and housing configurations. Beampatterns and relative angle responses are presented for an improved array and compared to the previous patterns and phase responses. The discussion and experimental results are limited to arrays constructed with piezo-ceramic bars resonant at 300 kHz, and intended for shallow water use.