Asymmetric and Symmetric Single-Pole Double-Throw With Improved Power Handling Using Indirectly Heated Phase-Change Switches

Abstract

Four-terminal indirectly heated phase-change switches (IPCSs) have emerged as excellent candidates for radio-frequency integrated circuit (RFIC) applications due to their state-of-the-art cutoff frequency, nonvolatility, CMOS compatibility, and exceptional linearity. However, IPCS performance is limited by relatively low-power handling capabilities in the off-state, limited by the Ovonic threshold switching (OTS) phenomenon. In this article, we propose the use of a quad configuration consisting of two series-connected IPCS in parallel with another two series-connected IPCS. This series connection increases the effective threshold voltage, thereby enhancing power handling compared to a single device. We experimentally demonstrate the implementation of this quad configuration in asymmetric and symmetric single-pole double-throw (SPDT) switches. Fabricated using an in-house process, these designs achieve an insertion loss (IL) below 0.8 dB and isolation higher than 17 dB within the dc-15 GHz frequency band. Furthermore, we explore techniques, such as reducing the probing pads and series-shunt configuration, to boost isolation beyond 30 dB. Thanks to the quad configuration, the threshold voltage increases from 5 to 13.5 V, predicatively enabling power handling above 35 dBm.