A Novel Real-Time Self-Monitoring Ka-Band MEMS Power Divider/Combiner for GaAs MMIC Application

This letter proposes a novel real-time self-monitoring Ka-band microelectromechanical system (MEMS) power divider/combiner. It is based on inline detecting a certain proportion of coupled power from the power divider/combiner through utilizing thermoelectric RF MEMS power sensors. In order to realize the real-time power self-monitoring, the power sensors based on Seebeck effect are located at three ports of the divider/combiner, where each sensor is composed of a power coupler, a pair of terminal matching resistors and a thermopile. In structure, several MEMS air bridges connecting the separated ground wires and a circular T-type structure are used for reducing parasitism and chip area. To obtain less RF loss and better isolation, this device is optimized and analyzed. This MEMS power divider/combiner is compatible with the gallium arsenide monolithic microwave integrated circuit (GaAs MMIC) process. Experiments demonstrate that the return loss (S11) is about -25 dB at the center frequency of 35 GHz and less than -12 dB in the frequency range of 30-40 GHz, and the insertion losses (S21 and S31) are close to -5 dB and the isolation (S23) is about -20 dB in the interested band. Measured sensitivities of the power sensors are more than 2.5 mV/W for the port 1 and about 0.8 mV/W for the ports 2 and 3. Using the resulting power ratio, these sensors are able to monitor the performance of the power divider in real time.