High frequency STW resonator filters

The authors present results obtained in the 1-GHz-2-GHz region for surface transverse wave (STW) resonator filters implemented using inline coupled (RFI) and combined mode resonator filter (CMRF) techniques. The STW device performance is strongly dependent on the surface confinement of the acoustic wave. In an inline resonator filter the inner grating serves the dual purpose of trapping the energy near the surface and providing the proper coupling between the two ports, making the periodicity of the inner grating a more critical parameter than in a combined mode device. Results show the effect of changing the periodicity of the inner grating on the overall response of the RFIs. The performance of combined mode resonator filters at 1 and 2 GHz is reviewed. Phase noise measurements for the 1-GHz CMRF device are presented, and the effect of changing the metal thickness on the overall device performance is demonstrated