Extremely low-loss SAW filter and its application to antenna duplexer for the 1.9 GHz PCS full-band

An antenna duplexer for the 1.9 GHz PCS-band handsets is realized by developing extremely low-loss and ultra-steep cut-off SAW filters. In this paper, design techniques to achieve the characteristics that satisfy all severe specifications required for the PCS-band duplexer is presented. Developed SAW duplexers have the insertion loss of -2.0 dB and -3.2 dB in the Tx and Rx band, respectively. Also, the attenuation levels are -53 dB and -45 dB. The device size is as small as 5/spl times/5/spl times/1.5 mm/sup 3/. These performances are sufficient for the PCS duplexer to be practical.