An electrical equivalent circuit model for RF MEMS disk resonators

An electrical-equivalent model for a RF MEEMS disk resonator is presented. A two-port ladder circuit is synthetized by discretizing the differential equation for the radial propagation of acoustic waves in the disk. Also, models of capacitive transducers are included in the circuit to model the bi-directional electromechanical coupling in the air gap. The circuit is nonlinear and can be used in any analyses including AC, transient and harmonic balance (HB) simulations. The model accepts physical parameters; no extraction of effective parameters for the circuit elements are needed. The wave propagation two-port model is verified by comparing its characteristics with the mathematical model. The accuracy of the model vs. the number of sections is studied. Also, the contribution of the supporting stem and the disk height are studied with FEM analyses. Finally, the predicted resonant frequencies are compared with the measured ones.