  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.
