Intermodulation distortion of actuated MEMS capacitive switches

For the first time, intermodulation distortion of micro-electromechanical capacitive switches in the actuated state was analyzed both theoretically and experimentally. The distortion, although higher than that of switches in the suspended state, was found to decrease with increasing bias voltage but to depend weakly on modulation frequencies between 55 kHz and 1.1 MHz. This dependence could be explained by the orders-of-magnitude increase of the spring constant when the switches were actuated. Additionally, the analysis suggested that increasing the spring constant and decreasing the contact roughness could improve the linearity of actuated switches. These results are critical to micro-electromechanical capacitive switches used in tuners, filters, phase shifters, etc. where the linearity of both suspended and actuated states are critical.