A novel in-line type frequency detector based on MEMS membrane for X-band application

In this paper, a novel in-line type frequency detector is proposed based on MEMS Membrane for X-band application. In the design, a MEMS membrane stands above the signal line of the CPW transmission line and acts as a coupling capacitance. A certain percentage of the input power, as a function of frequency, is coupled to the microwave power sensor. Finally, the frequency of the incident RF signal is deduced by measuring the output thermovoltage of the power sensor based on Seebeck effect. The incident power is not dissipated completely and the proposed design can achieve inline frequency detection. The inline type power sensor is designed, modeled and fabricated by GaAs MMIC process. The measured return loss is less than -13dB and the insertion loss is close to 1.3dB over 8-12GHz. The RF frequency measurement shows the output thermovoltage increases with the frequency. However, the poor frequency performance of the power sensor leads to the deviation of the measurement and theory.