A novel in-line type frequency detector based on MEMS technology and the GaAs MMIC process

In this paper, a novel in-line type frequency detector is proposed based on a MEMS membrane for X-band applications. In this design, the MEMS membrane stands above the signal line of the CPW transmission line and acts as a coupling capacitance. A certain percentage of the incident power, as a function of the frequency, is coupled to the microwave power sensors. Finally, the frequency of the incident RF signal is able to be deduced by measuring the output thermovoltage of the microwave power sensor based on the Seebeck effect. The design, lumped equivalent circuit model and simulation are presented. The in-line type power sensor is fabricated by the GaAs MMIC process based on MEMS technology. The measured return loss is less than -13 dB and the insertion loss is better than 1.3 dB over the frequency band of 8-12 GHz. The RF frequency measurement demonstrates that the output thermovoltage increases from 0.22 to 0.35 mV when the frequency varies from 8 to 12 GHz under the input power of 10 dBm.