Design of sonar receivers for shallow water buried object imaging

Abstract

Downward looking synthetic aperture sonar can detect and localize proud and buried objects, such as unexploded ordinance (UXO), in very shallow water environments. These sensors generate three-dimensional imagery from a two dimensional array that is a hybrid of a synthetic and real aperture sonar. Achieving high-resolution imaging with these sensors places stringent requirements on the sonar hardware. The acoustic signals generated by the sensor are wide bandwidth, low frequency, and high dynamic range. Receiver spacing and directivity also play an important role in image quality but create competing design constraints at low frequency. This work will present the results of a recent design study to develop receivers for a buried UXO imaging system. Achieving the stringent hardware requirements necessitated that the transducers, baffle, housing, and electronics were designed in concert. Finite element and one-dimensional models were used to evaluate several candidate designs based upon piezocomposite, spherical, and hemispherical transducers and identify tradeoffs with each. The analysis will focus on both simulated and experimental results of the receiver components. Results from the component level also informed system level models to quantify the point spread function and resolution improvement of the sensor.