A 0.1–40 GHz broadband MEMS clamped–clamped beam capacitive power sensor based on GaAs technology

This paper presents a 0.1–40 GHz broadband MEMS capacitive power sensor based on GaAs technology. An impedance compensation method utilizing a T-matching network is proposed to expand bandwidth. A lumped parameter model is established, the reflection coefficient, the voltage on the membrane and the sensitivity of RF-power detection are derived based on the multi-reflection transmission line theory. Performances of different up-states before pull-in are analysed when the membrane is electrostatic actuated. The proposed capacitive power sensor has been fabricated using GaAs process and MEMS technology. A controllable lateral etching technique is used to improve the sensitivity of RF-power detection and a low-spring-constant membrane is obtained. Measurement results show that return and insertion losses (S₁₁ and S₂₁) are less than −20.31 and 0.29 dB up to 40 GHz, respectively. DC voltage measurement indicates a low pull-in voltage of 10 V. Sensitivities of different operating frequencies are measured to be 11.6 aF mW⁻¹ at 5 GHz, 11.3 aF mW⁻¹ at 15 GHz, 10.8 aF mW⁻¹ at 25 GHz and 10.4 aF mW⁻¹ at 35 GHz. Frequency dependence measurements show a decreasing trend of sensitivity with the increase of frequency. (paper)