Interdigital transducer for surface acoustic wave filter, has same phase excitation and reflection in several base cells

摘要

The transducer consists of n base cells of length lambda, where lambda is the wavelength corresponding to the center frequency of the transducer, including exciting and reflecting base cells. The reflection contribution of each base cell has an intensity mR0, where m can be approximated to -2,-1,0,1 or 2 and R0 is a reference reflection. Each non-zero reflection contribution has the same phase, and the excitation has the same phase and intensity. The number of excited fingers is identical in all excited base cells. Excitation and reflection has the same phase in one direction, and the opposite phase in the opposite direction. An Independent claim is included for the use of the transducer for a low insertion-loss, extended impulse-response intermediate frequency filter.