10E-1 A New Unidirectional Transducer Using Proximity Coupling Between Bidirectional Tracks

Usually, directivity is obtained in SPUDTs by cascading reflective cells and transduction cells in the same acoustic track. An alternate approach was presented by G. Martin et al. who described a SPUDT using two tracks. The first track had only sources while the second track had sources and reflectors. The directivity was created by proximity coupling of these two tracks. The drawback of the original structure is due to the low aperture needed to get enough coupling between the tracks. A new device based on a similar approach is presented. The number of tracks is increased to obtain lower impedances and more efficient transduction cells are used. We called this new device the proximity-multi-track unidirectional transducer or PMUDT.