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A new low-loss, high-power SAW filter has been developed for an antenna duplexer used in an 800-MHz portable telephone transceiver. The new ladder-type configuration uses SAW resonators and capacitors between electrode fingers and the earth. It is fabricated on a 2-mm-square LiTa03 chip. This configuration provides insertion loss as low as 1.0-1.2 dB and output power up to 2 W at 800 MHz. Experimental results of a miniature antenna duplexer module using this filter as a transmitter filter and the previously published high-performance SAW filters as receiver filters are also presented. This module also includes a receiver low-noise amplifier, yet its size is under 8 ml.

New orientations for longitudinal leaky SAW with small propagation losses and high velocities in lithium niobate (LN) and lithium tantalate (LT) have been found. Their velocities are 6100 to 6500 m/s in LN and 5200 to 5800 m/s in LT. Their propagation losses are almost negligible only in the case of an Al-grating structure. For example, the Al thickness relative to the SAW wavelength must be 8.4% for 171 degrees YZ'-LN; for 133 degrees YZ'-LT, the value must be 9.2%. These propagation properties were obtained by using a simulator that combined both finite-element and analytical methods. These results were also well confirmed by measuring the impedance responses of one-port SAW resonators.

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