High isolation X-band MEMS capacitive switches

Abstract

This paper presents the design and optimization of the X-band microelectromechanical system (MEMS) capacitive switch using an electrical model and a mechanical model. The electrical model can accurately extract the resistance, capacitance and inductance of the switch. Based on the electrical model, a single-bridge switch and double-bridge switch with serpentine folded suspensions are proposed to achieve higher isolation compared to a typical MEMS capacitive switch at X-band frequencies. The measurement results show an isolation of 16.5–28 dB for single-bridge switch and 25–35 dB for double-bridge switch, both at 10–13 GHz. The mechanical performance is measured using an optoelectronic laser interferometric system. Due to the low effective spring constant of the serpentine folded suspensions, only 20.4 V of pull-down voltage is required. An improved fabrication process using surface and bulk micromachining techniques is also described.