Enhancing RF MEMS SPDT switch performance through fabrication and ground balance

Abstract

Abstract

Abstract RF MEMS switches are gaining attention as an alternative to solid-state switches due to their low loss, high isolation, and excellent linearity. Although many SPST designs are reported in the literature, multiport switches, especially SPDT switches, remain limited despite their key role in phase shifters, antenna switching, and transceiver systems. In CPW-based SPDT switches, residual stress in the beam and grounding effects strongly influence pull-in voltage, beam deformation, insertion loss, and isolation. This work presents the complete development of an SPDT switch from design to measurement. Short- and long-path layouts are evaluated, with the short path showing better return loss. A solid cantilever initially requires a high pull-in voltage, which is reduced by introducing two windows near the anchor and tip, resulting in better damping and more stable contact. The fabrication process is also optimised to mitigate stress in the switch. After fabrication, a high insertion loss is observed due to the absence of a common ground. To overcome this, double wire-bond ground bridges are implemented to equalise the grounds, significantly improving insertion loss and yielding smooth isolation across the 100 MHz – 20 GHz range.