High-Capacitance-Ratio Warped-Beam Capacitive MEMS Switch Designs

This paper presents a detailed analysis of the design, fabrication, and testing of a high-isolation electrostatically actuated capacitive shunt switch for X-band applications. The dual-warped-beam switch´s RF performance is fine-tuned simultaneously in the off and on states by introducing warped bimetallic beams to the switch´s edge to increase the effective capacitive area in the downstate and to the switch´s center to decrease the effective capacitive area in the upstate. As a result, the dual-warped-beam switches demonstrate an off-to-on capacitive ratio of up to 170 without the need for thin dielectrics or high dielectric constant materials, exhibiting excellent RF performance. High isolation at X-band of less than 40 dB is also obtained with the introduction of inductive meandered springs into the switch structure. This novel tuning design mechanism for capacitive switches utilizing warped bimetallic beams has the advantage of simplicity and flexibility without the added complexity of using thinner dielectrics, tuned circuits, or larger size.