Simulation of short LSAW transducers including electrode massloading and finite finger resistance

摘要

The theory for the 2-D numerical analysis of acoustic wavengeneration from finite length leaky surface acoustic wave (LSAW)ntransducer structures is presented. The mass loading of the electrodesnis incorporated through the use of the finite element method (FEM). Thensubstrate is modeled using both analytical and numerical means. Thenadvantages of this simulation are twofold. First, it is capable ofnextracting the individual bulk wave conductances from the overallnconductance of a given device. At large distances from the transducer,nthe angular distribution of power radiated relative to the substratensurface can then be calculated for each of the three possible bulk wavenpolarizations. The second advantage of the simulation is that the effectnof finite electrode resistance is included through the use of a seriesnequivalent resistance for each electrode in the structure. Once thenresistance for each electrode in the structure has been determined, thenoverall effect on the device admittance is modeled by applying anconstrained minimization process to the electrical boundary conditionsnof the transducer. To conclude the paper, the simulation will bencompared against the experimental admittance of a 37-finger uniformntransducer with a metallization ratio of 0.5 on 42°nLiTaO3. The agreement between theory and experiment isnexcellent