SAW duplexers without λ/4 phase shifter for CDMA cellular phone systems

We have already reported a front-end SAW duplexer for Japanese PDC 800 MHz cellular phones with wide channel separation of 112 MHz between Tx and Rx band (Onizuka, T. et al., Proc. IEEE Ultrason. Symp., p.2101-4, 2003). We now describe an application of the SAW duplexer which has narrow channel separation by using SAW resonator in which arbitrary pole and zero frequencies are controlled by adding an external inductor and/or capacitor. For example US-CDMA and J-CDMA cellular phone systems have a very narrow channel separation and broad bandwidth. We fabricated duplexers for each system by using our unique technique, and developed low insertion loss, high attenuation and high isolation characteristics.