Calculation of Transformer Ratio in Mason's Equivalent Circuit for cMUTs

We present a new method to calculate the transformer ratio of a cMUT in Mason's Equivalent circuit model. The effect of the spring softening capacitance is also included in the analysis. We use the existing turns ratio calculation methods as a starting point to calculate the force-voltage ratio at the secondary of the transformer and the input port of the circuit. We use this ratio and the capacitances in the Mason's circuit to find the actual turns ratio. Different methods are discussed for the calculation of the equivalent circuit parameters. We show that the transformer ratio has a bounded maximum at collapse voltage. We also investigate the effect of electrode size on the transformer ratio. Transformer ratio decreases with decreasing electrode size.