A spatially shaded PVDF acoustic transducer

In an effort to design a transducer having low sidelobes in the radiation pattern but requiring only a single amplifier, the technique of spatial shading is explored. This method uses an array of small elements, each driven uniformly but randomly distributed along the transducer with a density distribution that matches the desired shading. As the individual elements shrink and their packing density increases, the theoretical radiation pattern approaches that of the ideal shading. The design of a 500-kHz stave transducer having a 2° wide Gaussian radiation pattern, using λ/4 long elements, is presented. The elements were placed using a Monte Carlo approach, and a theoretical sidelobe level of -21.8 dB was achieved. A transducer with this element distribution was built using 110-μm-thick polyvinylidene fluoride (PVDF). Experiments reveal a radiation pattern very close to the predicted pattern, with -20.8-dB sidelobes