P5H-2 Novel SAW Network Model Parameter Extraction Technique

Traditionally, parameters for surface acoustic wave (SAW) scalar models have been determined either experimentally or by fitting dispersion expressions describing the models to numerically computed grating dispersion curves. Experimental parameter extraction is costly and labor intensive. The latter technique offers significant time and cost savings but normally yields frequency independent parameters, which may compromise modeling accuracy for large bandwidth devices. Thus, there is a need to accurately determine frequency- dependent parameters for SAW scalar models. This paper presents a new procedure for extracting frequency- dependent SAW scalar model parameters for finite thickness electrodes and arbitrary substrate orientations, including natural single phase unidirectional transducer (NSPUDT) directions. Equivalent network model (NM) parameters have been extracted for platinum (Pt) electrodes on STX and ST25 orientations of quartz, Euler angles (0deg,132.75deg,0deg) and (0deg,132.75deg,25deg), respectively. Two-port SAW resonators with Pt electrodes were fabricated on STX and ST25 quartz to verify the extracted model parameters, and the frequency of peak | S211 is predicted to within 412ppm of measured values. This new extraction technique has proven both accurate and robust; NM IDT admittance consistently agrees with FEM/BEM calculated and experimentally measured device responses, and extracted parameters are not significantly dependent on the length of the grating structures analyzed.