Hideki Ohmori

Development of ladder type SAW RF filter with high shape factor

The paper presents ion implantation technology to improve the shape factor of a ladder-type SAW RF filters for mobile communication systems. The improvement of the shape factor was confirmed experimentally. However we found that the SAW phase velocity is decreased by ion implantation. To stabilize and recover the SAW phase velocity, several annealing conditions were investigated. At the annealing condition of over 450/spl deg/C/spl times/1 hour, SAW phase velocity was recovered to almost the same as the initial velocity. In the past, the shape factor values of ladder-type SAW filters using a LiTaO/sub 3/ substrate have been almost 1.7. The ion implantation technology has been applied to a PDC (personal digital cellular) -1.5 GHz SAW band pass filter using a LiTaO/sub 3/ substrate. We have obtained the shape factor value of 1.4 under the following conditions; ion: double charge Ar/sup ++/, dose: 5/spl times/10/sup 13//cm/sup 2/, acceleration voltage: 180 keV.

A study of SAW antenna duplexer for mobile application

This paper describes the evaluation results and new proposal of the surface acoustic wave antenna duplexer especially its reliability and how to use it in the portable system. When high power applied to a device, SAW resonator constructing a filter generates heat, which comes from electrical and mechanical loss. Optimal design was studied by thermal analysis in order to avoid heat concentration of filter. New proposal was investigated to protect Electro static discharge (ESD) and to obtain better attenuation in 2/sup nd/ and 3/sup rd/ harmonics range by adding an external circuit.