A shear horizontal (SH) wave is excited by composing interdigital transducers (IDTs) and reflectors consisting of films made of heavy metal on ST cut 90°-X propagation quartz substrate (propagation direction is perpendicular to X-axis). This wave has a large electrochemical coupling factor, a large reflection coefficient and an excellent temperature characteristic. The square of the electromechanical coupling factor is 2.0∼2.6 times, the reflection coefficient at reflector's grating electrodes is 30 times as large as that of Rayleigh wave on an ST cut X propagation quartz substrate, and the temperature coefficient of frequency is equal to that. The authors applied this SH wave to filters for the first intermediate frequency (first IF) stage of a global system for mobile communications (GSM). As a result, we succeeded in developing the low loss and very small-sized filter (3×3×1.03mm; typical dimensions) having a high rejection out of band for the first time.
ASJC Scopus subject areas
- Acoustics and Ultrasonics