A coupling RF MEMS power sensor based on GaAs MMIC technology

A wideband 8-12 GHz inline RF MEMS power sensor that is based on sensing a certain percentage of the incident microwave power coupled by a MEMS membrane is presented, and the sensor is accomplished with GaAs MMIC technology. In order to improve microwave characteristics and the frequency response of the output at X-band, an impedance matching structure and a capacitance compensating structure are proposed in the paper. The design of the power sensor with the improved structures has resulted in the measured reflection loss of the sensor less than -17 dB, the insertion loss less than 0.8 dB, and the flatness of the frequency response at X-band. A sensitivity of more than 26 mu V mW(-1) and a resolution of 0.316 mW are obtained at 10 GHz under the normal ambient temperature. The experiment demonstrates the immediate effect of the modulation depth under amplitude modulation (AM) signals on the sensitivity of the sensor. In addition, the measured mechanical resonant frequency (f(o)) of the MEMS membrane of the sensor is 110 kHz. The measured results show that the intermodulation (IM) power for Delta f = 80 kHz, P-1 =P-2 =10 dBm of the signals is less than -52 dBm, and the input third-order intermodulation intercept point (IIP3) is a large value at Delta f=f(o), so the inline RF MEMS power sensor for Delta f>f(o) will not generate significant intermodulation distortion. (C) 2010 Elsevier B.V. All rights reserved.