Simulation analysis of SMR with tetrahedral amorphous carbon as high impedance material of Bragg reflection

To improve the electricity and acoustic quality of solidly mounted resonator(SMR), realize the new application of tetrahedral amorphous carbon(ta-C) in the field of bulk acoustic wave device, a SMR was designed with ta-C as the high acoustic impedance Bragg reflector, which to simulate the effect of the Bragg reflector to the properties of SMR, as well as the influence of the sp ³ fraction in ta-C and the error of thickness of high/low acoustic impedance layers on quality factor(Q) by MathCAD. The simulation results showed that the quality of SMR was improved with the increase of Bragg reflectors. With higher sp ³ fraction, saturated Q factor can be reached with fewer layers, and there should be only six layers (three pairs) in order to get an excellent Q factor when the sp ³ fraction in ta-C was 80%. The thickness error of high/low acoustic impedance layers closer to the piezoelectric stack had greater effect to Q factor. So the design of SMR with high frequency (8 GHz) and low loss has been realized.