Constant beamwidth transducers: A tribute to Kim Benjamin

Constant beamwidth transducer (CBT) is a special acoustic transducer, where acoustic beamwidth is independent of frequency, because of its Legendre polynomial normal velocity distribution on the surface of transducer spherical dome. By elegant design of Legendre polynomial normal velocity distribution profile on the transducer radiation surface dome, acoustic sidelobes can also be controlled and eliminated. To achieve Legendre polynomial normal velocity distribution, electrode area shading is one of important techniques to design a practical CBT. in this paper, the CBT designs, shading patterns, size effects, frequency band limit, build of materials, as well as Mr. Kim Benjamin critical contributions in the field toward a U. S. Navy standard CBT transducer at the Underwater Sound Reference DivNpt (USRD) will be summarized.