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February 2024

Optimized PCM Switches and Capacitors: Basic Building Blocks for RF and Microwave Subsystems

by Pierre Blondy, Nicolas Le Gall, Idoia Ugarte Olcoz, Ines Bettoumi, Mohammed Lajaate

Abstract: This paper presents refinements for Phase Change Material (PCM) switch designs with Germanium Telluride (GeTe) alloy for RF and microwave switches and switched capacitors. PCM techniques rely on a heater to initiate a GeTe phase change that is bistable in the on state or the off state without any applied bias. The novel design presented uses the heater as an RF access to reduce the size of the switch, and the PCM switch is proven in the paper to maintain Q reasonably well in either state. PCM switches compete favorably with MEMS, RF-SOI CMOS switches for many switch and switched capacitor applications with port-to-port isolation better than 30 dB from 100 MHz up to 40 GHz, switching times of 100-500 nsec to switch off and 1-2 ┬Ásec to switch on. Innovative variable capacitor applications are envisioned for tunable microwave circuits.