RF MEMS Thermistor Power Sensor Based on Wheatstone Full-Bridge Structure

In this paper, we have first proposed a RF MEMS thermistor power sensor based on Wheatstone full-bridge structure. The proposed RF MEMS thermistor power sensor is fabricated using GaAs MMIC (monolithic microwave integrated circuit) technology. In this device, two parallel low TCR (temperature coefficient of resistance) heaters are employed to keep the impedance match stable. And a Wheatstone full-bridge formed by four identical thermistors is used for the unknown RF power measurement. To improve the sensitivity of the sensor, a MEMS substrate membrane is fabricated beneath the hot area to suppress longitudinal heat loss by back etching process. The whole structure is integrated with CPW transmission line, which has the potential of high integration density. Compared with traditional thermistor power sensor, this device has both advantages of stable impedance match and high sensitivity.