A low frequency high resolution sonar for AUVs

The authors present the design of a sonar for autonomous underwater vehicles (AUVs) which can be operated as a conventional high-frequency forward-looking sonar or as parametric low-frequency sonar for buried mine detection and as an enhanced target classifier through the use of wideband low-frequency waveforms. The system provides high area coverage rates in conventional high-frequency mode when searching for water column and proud targets on the bottom. When detecting buried mines, the typical low coverage rate of a parametric system is improved by using pseudo-random binary sequences to code the transmit waveforms, thus supporting a send-while-receive mode operation. Additionally, the parametric beam can be used to provide improved water column and proud bottom target classification over conventional systems through the use of low-frequency wideband waveforms. Since the low-frequency source is parametric, the transducer size and weight is considerably less than that of a conventional projector at low frequencies