3D Hybrid Capacitance Model for Angular Vertical Comb Drives

Theory and examples of a 3D hybrid analytical-heuristic capacitance model for angular vertical comb (AVC) drives are introduced. The model considers relative position and orientation of finger electrodes as well as geometric properties like finger height, length, average thickness, gap distance and offset in respect to the finger's mechanical rotation axis. The presented model is implemented as MATLAB (TM) [1] class and into SUGAR [2] net list simulator. Within this paper, the capacitance output of the hybrid model is compared to the results of 3D finite element analysis (FEA) data performed with ANSYS [3] and other alternative methods for two common test cases. The results show good agreement with 3D FEA and smooth first order derivatives. The capacitance uncertainty of the proposed hybrid model in respect to a 3D FEA expressed in terms of a normalized root mean square (RMS) is in the range of 5-6%.