TEMPERATURE STABLE ONE-PORT SAW RESONATORS

One-port SAW resonators with improved temperature stability were suggested by Takagi et al. This solution represents a double resonator of two single resonators on STX quartz the turnover temperatures of which are positioned below and above room temperature, respectively. Coupling of the single resonators is implemented by the waveguide effect. Both the temperature coefficient of frequency of 1st and 2nd order (TCF1, TCF2) are compensated. The purpose of this paper is to present a double one-port SAW resonator the single resonators of which are characterized by using different propagation angles (angle between the propagation direction and the X axis) on one of the ST cuts of quartz in vicinity of the propagation angle where the TCF1 vanishes. The coupling is now achieved by a series connection of two parallel connections of a single resonator and of an inductance. The compensation of the TCF1 and TCF2 is demonstrated by simulations as well as by experiments. The TCF2 can be compensated by choosing the inductances in a suitable manner whereas the TCF1 is compensable by adjusting the inductance ratio. Double resonators on 35.5 degrees rotY quartz were investigated experimentally.