Capacitive RF MEMS power sensors

Two novel RF MEMS power sensors operating up to 5 GHz and 45 GHz respectively have been designed. The lower frequency device is a coplanar transmission line with released ground sections. The rms voltage across the conductors causes the released ground lines to bend towards the signal line in the middle. This bending can be detected capacitively with a pair of sense electrodes. The higher frequency device extends a Si plate, which is metallized underneath, above a coplanar transmission line. The electrostatic force due to the rms voltage pulls the Si plate towards the transmission line, which can again be detected with a pair of sense electrodes. Microwave simulations indicate that input match better than -30 dB and transmission loss less than 0.2 dB up to 45 GHz can be achieved. For the 5 GHz design a power resolution of -39 dBm and -37 dBm for the 45 GHz design have been obtained by analysis. Measured results for the first generation 5 GHz device show input match better than -15 dB and transmission loss less than 0.7 dB. Measured results from the 45 GHz device do not exist yet