Measurements on Intermodulation Distortion of Capacitive Power Sensor Based on MEMS Cantilever Beam

This letter presents an experimental study of intermodulation (IM) distortion of the capacitive power sensor based on MEMS cantilever beam for the first time. The return loss is less than -25 dB and the insertion loss is close to 0.1 dB at 8-12 GHz, indicating the good microwave performance. The input power dependence measurement implies that the third order intermodulation (IM3) increases with the input power and the slope of curve is ~ 3.39, 3.16, 2.94, and 2.93 under Δf=100, 200, 500 kHz, and 1 MHz, respectively. In addition, the frequency difference dependence measurement shows that a rapid decrease of the IM3 products is observed when Δf varies from 10 Hz to 200 kHz, while a slow decrease is observed from 200 kHz to 2 MHz. The experimental results demonstrate that the power sensor is easy to be disturbed by two signals with Δf less than 200 kHz. When Δf exceeds 200 kHz, the IM3 is small and significant IM distortion will not generate.