Adaptation of new transducer materials in the design of a bathymetric multi-beam system

In recent years, multi-beam systems have gained widespread acceptance as the hydrographic surveyor's tool of choice for many reconnaissance as well as survey applications. In this discussion, the implementation of a Mills Cross transducer employing PVDF material as receiving elements is considered, as is the architecture of the associated swath bathymetry system. The projector is a curvilinear array creating a 2.5/spl deg//spl times/100/spl deg/ fanbeam. The system departs from conventional multi-beam designs which utilize phased array beam forming techniques for the receiving array, by incorporating thirty discrete PVDF receive elements, each element forming a 3/spl deg//spl times/15/spl deg/ beam. The receiving elements are oriented 3 degrees apart such that the 30 receivers cover a 90/spl deg/ swath. Receiving elements are comprised of 0.5 mm thick PVDF shaped to provide a sidelobe suppression of -30 db. With this design approach, artifacts intrinsic to electronically formed beams are eliminated. This simplifies signal processing, improves system accuracy, and lowers the overall system cost. Both theoretical simulations and experimental data for the Mills Cross configuration of the projecting and receiving elements is presented.