Study of high isolation techniques for surface acoustic wave duplexer modules

The isolation characteristics between transmitter and receiver ports for surface acoustic wave (SAW) antenna duplexer modules are studied. Three new techniques are developed to achieve the desired isolation performances in this study. Optimized phase shifter conditions are solved analytically. An improved switching circuit is proposed for cancellation of the inductive element of a pin-diode. A design rule of distance between two lines for SAW antenna duplexer modules is also proposed. The obtained condition and circuit are applied to an extended global system for mobile communication/digital cellular system (EGSM/DCS) dual-band and an extended global system for mobile communication/digital cellular system/personal communication system (EGSM/DCS/PCS) triple-band SAW antenna duplexer modules. Sufficiently high isolation characteristics are obtained.