A 25–50 GHz Phase Change Material (PCM) 5-Bit True Time Delay Phase Shifter in a Production SiGe BiCMOS Process
Dimitrios Baltimas, Gabriel M. Rebeiz
Abstract
This paper presents the implementation and measurement results of a wideband (DC-67 GHz) phase change material (PCM) switch and a miniature 5-bit true time delay (TTD) phase shifter. A series-shunt single pole double throw (SPDT) switch is implemented based on the 4-terminal PCM switch integrated in the back-end-of-line (BEOL) of Tower Semiconductor SBC18H3 0.18 µm SiGe BiCMOS process. The PCM Switch core has a nominal <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$R_{ON}$</tex> of 3 Ω and a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$C_{OFF}$</tex> of 4 fF leading to a FoM of 12 fs. This core performance leads to a wideband SPDT IL of 0.9 dB at 30 GHz and to 45 dB of isolation. Using the SPDT switch, a 5-bit 0–124 ps TTD unit with a transmission line based implementation is presented. It exhibits an RMS group delay error of less than 2 ps from 25–50 GHz and less than 3 ps from 6–55 GHz.