Development of 800 MHz band SAW filters using weighting for the number of finger pairs

Abstract

A surface acoustic wave (SAW) bandpass filter has been developed for pocket and mobile telephones for 800-MHz-band cellular radio systems. In developing this filter, it was found that the number of finger pairs suppressed the sidelobe. The number of finger pairs was varied for each input and output transducer which composed an interdigitated interdigital transducer (IIDT) structure. The proportion of weighting for the number of finger pairs was optimized using computer simulation. A transmitting filter for AMPS was constructed using this method. Sidelobe suppression improved to above 8 dB compared to no weighting. Absolute suppression was less than -24 dB. This filter has properties suitable for practical use in a temperature range from -30 to +70 degrees C.<>