A triple-beat-free PCS SAW duplexer

In general, surface acoustic wave (SAW) duplexers have the lower 3rd order linearity compared to bulk acoustic wave (BAW) duplexers. Actually, the specification for the inband 3rd order nonlinear distortion, triple beat, required for 1.9 GHz Personal Communications Service (PCS) band in CDMA2000 can be satisfied only by BAW duplexers. The objective of this work is to propose the design methodology for extremely high-linear SAW duplexers and to develop the triplebeat-free PCS SAW duplexers. The nonlinear elastic model, which we have proposed last year for predicting the triple beat, is applied to design the highly linear PCS SAW duplexers. The developed SAW duplexer achieves the extremely high linearity of approximately -90 dBc in the triple beat test, which is 20 dB better than the conventional duplexer keeping the equivalent filter characteristics and same packaging size. To the best of our knowledge, this is the first PCS SAW duplexer which satisfies the triple beat specification required in CDMA2000.