Source equalization for SPUDT transducers

The electroacoustic source strength for a periodic SAW transducer can be determined analytically. With the exception of sources close to the ends of the transducer, the source strength function does not depend on its position in the transducer. A Distributed Acoustic Reflection Transducer (DART) is not periodic and consists of two or more linewidths and strip periods. The source strength and effective source position of a strip is dependent on the widths and positions of the adjacent strips. Strips of a given width can exhibit source strength differences of 10% or more depending on their position in the DART. This paper presents two methods for predicting the source strength and effective position of a source in a DART. The first method uses an electrostatic Green´s function analysis. The second more complete method uses a mixed FEM/BEM analysis to obtain a more accurate result. Results of these two methods are compared for various transducer configurations. Using the above results a 112 MHz filter was designed and built on a 112°YX LiTaO ₃ substrate