A modified proposed capacitance model for step structure capacitive RF MEMS switch by incorporating fringing field effects

This paper presents a new expression for the capacitance model based on ligament efficiency. The parallel plate capacitance is the first component derived based on the percentage of ligament efficiency and the second component which is fringing field capacitance is the combination of both existing Yang's fringing field developed by the perforations and Meji's capacitance model developed for fringing field due to sidewalls of parallel plates. The proposed model is the combination of three components and enhances accuracy to estimate the total capacitance. The proposed model contributes up to 10% and 2% of the fringing field in upstate capacitance and downstate conditions. The proposed capacitance model is validated by designing in FEM tool to obtain the deviation between the results and respective deviation is expressed as the percentage of error which results from 0.013% to 2.10% in up and downstate conditions. The error percentages are analysed for different ligament efficiencies to obtain the optimum value to enhance the performance of the switch.