INTRODUCTION: A surface acoustic wave (SAW) deviceutilizes the wave propagation along the surface of asubstrate, with the vibration that typically penetrateseveral wavelengths into the depth of material.Recently, the generation of BAW modes in TC-SAWresonator on LiNO3 and its characteristics wereobserved experimentally in [1]. Based on COMSOLMultiphysics® simulation, we show that the generationof BAW modes were due to nonlinear materialproperties of LiNO3. Simulation results ofcharacteristics of BAW modes are compared withexperimental measurements in [1].

COMPUTATIONAL METHODS:

RESULTS: The TC-SAW resonators in [1] were made on128°YX LiNO3 substrate, with 100 electrodes pair inlength direction and 20 wavelengths in aperturedirection. The period was 2.3 um and two substratedepth were considered: 150 um and 500 um. Insimulation, 25 dBm power at fundamental frequency fwas input to the resonators. The BAW modesharmonically generated by the nonlinear materialconstants were identified. The output power availableat 1st, 2nd, 3rd harmonic with f, 2f, 3f were calculatedand compared with experimental measurements.

CONCLUSIONS:• BAW modes harmonically generated in SAW resonator

were simulated using COMSOL Multiphysics® andcompared with experimental results;

• The possible dominant generation mechanism wereidentified in the harmonic power levels.

REFERENCES:1. Solal, M., Kokkonen, K., Inoue, S., Briot, J. B., Abbott, B. P., & Gamble, K. J., Observation of

nonlinear harmonic generation of bulk modes in SAW devices, IEEE transactions onultrasonics, ferroelectrics, and frequency control, vol 64, 1361-1367, 2017

2. Y. Cho and K. Yamanouchi, Nonlinear, elastic, piezoelectric, electrostrictive, and dielectricconstants of lithium niobate, J. Appl. Phys., vol. 61, no. 3, 875-887, 1987.

Figure 3. FEM model f-SAW, 2f-BAW and 3f-BAW displacement modeshapes (left), and their respective electric potential mode shapes (right)of an 840.4 MHz 128°YX LiNO3 SAW resonator. H1 propagated in the X-direction whereas H2 and H3 travel in the Y-direction.

Figure 1. Schematics of measurement setup in [1] and presentationof generation of BAW modes in TC-SAW device.

Characterization of BAW Modes Harmonically Generated (f-2f-3f) in LiNO3

SAW Devices Using COMSOL Multiphysics® SimulationXiangnan Pang, Zinan Zhao, Yook-Kong Yong

Department of Civil and Environmental Engineering, Rutgers University, Piscataway, NJ, USA

Figure 2. (a) Simulation Flowchart and Interfaces in COMSOLMultiphysics; (b) Electrical connection of piezoelectric resonator indriving or detecting circuits: series (left) and parallel (right).

Figure 4. (a) Experimental measurement and (b) simulation results ofharmonic power in 128°YX LiNO3 SAW resonators.

Figure 5. (a) The effects of electrical connection and (b) differentnonlinear material constants on the harmonic signal in 128°YX LiNO3SAW resonators.

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Excerpt from the Proceedings of the 2019 COMSOL Conference in Boston