Coupling coefficient determination based on simulation and experiment for ST-Cut quartz saw delay-line response

This paper used the theoretical calculation to simulate the response of Surface Acoustic Wave (SAW) delay-line on quartz substrate and then compared to the experimental results. The coupling coefficients affected by operating frequency as well as aperture length were built up by experimental data analyzing. From these two parameters, the device coupling coefficient was defined. This is our new contribution and has not been mentioned in other document. This contribution helped improve the simulation results and help the analysis process more comprehensive. ST-cut quartz SAW delay-lines with gold inter-digital transducer (IDT) operating at 39.5MHz and 78.9MHz corresponding to 80 micron and 40 micron of the wavelength were developed. The differences of aperture length in IDT designs were investigated to help understand the effects of this parameter on SAW sensor response. The errors between simulation and experimental results are small. The maximum error of operating frequency is 1%; of insertion loss is 4.25% and 3.13% for bandwidth. The larger of the insertion loss error is explained to be the result of mathematical approximation and the quality of quartz substrate. The simulation results agree with the experimental results shows that the simulation method can be used for quartz-based SAW delay-line as well as for other material based SAW delay-line applications; the sensors functioned correctly and can be used. The results help understand more about the parameters which effect the insertion loss, operating frequency and bandwidth. It should be very useful for IDT design in specific, SAW sensor and SAW filter design in general.