High-power electro-mechanical behavior of a capacitive microwave power sensor with warped cantilever beam

Abstract

In this paper, high-power up to 4000 mW electro-mechanical behavior of a capacitive micro-electromechanical systems (MEMS) microwave power sensor using cantilever beam is investigated. Due to residual stress gradients, the power sensor is proposed for a warped cantilever beam connected to coplanar waveguide (CPW) structure. The proposed sensor is fabricated using the GaAs monolithic microwave integrated circuit (MMIC) process. It is demonstrated that the output response of this sensor exhibits non-linear characteristics under high power levels (more than 1000 mW). The measurement results can be classified as three regions: linear region (1–1000 mW), saturated region (1000–2500 mW), and over-saturated region (2500–4000 mW). Their corresponding sensitivities are 2.8 fF/W, 1.03 fF/W, and 0.32 fF/W at 10 GHz, respectively. The non-linear output response of the power sensor is mainly caused by impedance mismatch at X-band (8–12 GHz). Furthermore, an electro-mechanical model of power sensor based on warped cantilever beam is proposed. The results are well in agreement with the calculated ones using this model by software that employs the finite element method (FEM), which provides the potential prospect for the design of capacitive power sensor.