Patent ID: 6777855
Filing Date: 2004-08-17
Classification: H03H

Abstract:
A transducer comprising:base cells each having a length &lgr;, where &lgr; is a wavelength corresponding to a center frequency of the transducer, the base cells being arranged in a direction of propagation of a surface acoustic wave, the base cells including exciting base cells, the base cells including an excitation portion and a reflection portion, the excitation portion being non-zero for exciting base cells, the reflection portion of each base cell having a strength mR0, where m is one of âˆ’2, âˆ’1, 0, 1, or 2 and R0 is a reference reflection; wherein the base cells include electrode fingers, a width of the electrode fingers is not a multiple of &lgr;/16, and a separation between adjacent electrode fingers is not a multiple of &lgr;/8; wherein, in the direction of propagation, a non-zero reflection portion in each base cell has a same phase position &phgr;Â±&pgr;n, where n is an integer greater than zero; wherein centers of excitations of base cells having a same sign are separated by 2&pgr;n and centers of excitations of base cells having different signs are separated by (2nâˆ’1)&pgr;, and wherein surface acoustic waves excited and reflected in at least one base cell are equal in phase in the direction of propagation and opposite in phase in a direction that is opposite to the direction of propagation.