Stress-migration analysis on SAW duplexer

A SAW antenna duplexer (DPX) consists of a TX-filter, a RX-filter and a phase-shifter. They are demanded to be durable against 1.2 W of excitation power for several ten thousands hours. The filters, consisting of several parallel and series connected one-port resonators, contain high density SAW power and tend to deteriorate by the stress-migration of the aluminum electrodes. We analyzed the absolute values of each resonator-surface strain induced by resonant SAW energy using the numerical analysis method. Several facts are found that strains of aluminum film electrodes vary 2-3 times with driving frequency and that the connected condition of TX and RX filters through phase-shifter reduces resonators surface strains in RX filter for TX frequency band. Experimental life tests are also carried out. As a result, high textured Cu-doped aluminum on Ti film of SH-mode resonators on 36 Y-cut LiTaO3 proves to withstand for the 1.2 W driving power.