A 60 GHz Precise Reflection-Type Phase Shifter with Extremely Small Phase Shift, Based on GeTe Phase-Change Switches

This article presents the implementation of a millimeter-wave reflection-type phase shifter (RTPS) operating at 60 GHz, integrating a phase-change material (PCM), composed of germanium telluride (GeTe). Designed to feed an antenna array operating at 360 GHz, this phase shifter exploits a small 3-dB branchline coupler based on a coplanar waveguide (CPW) configuration, monolithically integrated with two identical reconfigurable reflecting loads. These loads consist of adjustable-length transmission lines (TL), enabling precise phase shift control. This is reconfigured using six non-volatile PCM switches in shunt configuration that selectively short-circuit line sections without consuming static power. The fully miniaturized device, with a footprint of 0.88 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, is manufactured using a 2-metal-layer microfabrication process. Experimental measurements show an average insertion loss of 4.36 dB, with a variation of just ±0.95 dB over a bandwidth of 10 GHz. The RTPS also exhibits linear phase shift over a frequency range from 52 to 62 GHz, with a measured minimum phase shift step of less than 2° as expected in simulation.