A Novel Capacitive Microwave Power Sensor Based on Double MEMS Cantilever Beams

In order to improve the sensitivity characteristic and the fabrication reliability, a novel capacitive power sensor based on double MEMS cantilever beams is proposed in this work. It is designed and fabricated using GaAs MMIC process and MEMS technology. A lumped circuit model is built to study the microwave characteristic of this capacitive microwave power sensor. The influence of impedance value and electric length of the coplanar waveguide on the microwave performance of the double MEMS beams are studied. The microwave characteristic of both ports are measured. The return loss of port A is from −11.5dB to −14.6dB, and the return loss of port B is from −12.1dB to −14.3dB at 8-12GHz. The insertion loss of port A is from −3.6 dB to −2.8dB, and the insertion loss of port B is from −3.7 dB to −2.9dB at 8-12GHz. The measured results show that this capacitive power sensor has a good microwave characteristic. The measured sensitivity of this capacitive microwave power sensor is about 51.6 fF/W @10 GHz, and the theoretical sensitivity is 55.97 fF/W. The relative error is 7.8%. Compared with the capacitive microwave power detection system based on single cantilever beam, the sensitivity characteristics have been greatly improved. It is valuable to realize the multiple beams detection technology and enable further interesting possibilities in the field of microwave power detection.