A new unidirectional transducer using proximity coupling between bidirectional tracks

Usually, directivity is obtained in single-phase unidirectional transducers (SPUDTs) by cascading reflective cells and transduction cells in the same acoustic track. An alternate approach was presented which described a SPUDT using two tracks. The first track had only sources but 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 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.