Sub-THz Phase Shifter Using a Photoconductive Solid-State Plasma Evanescent-Mode Waveguide Switched Stub

In this paper, we demonstrate the viability of photoconductive solid-state plasma for phase shifter applications in sub-THz regions. This two-state silicon micromachined waveguide phase shifter exhibits low insertion loss and promising figure of merit at G-band. Phase shifting is achieved by placing a shunt waveguide stub that is switched with a second order photoconductive evanescent-mode waveguide switch. In both states of the switch, an average extracted loss of 0.19 dB and return loss >10 dB is maintained while measuring a 12.2° phase shift at 190 GHz. This design demonstrates the feasibility of achieving a high figure of merit on the order of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$88^{\circ}/\text{dB}$</tex> at 184.6 GHz. These results highlight the exciting potential of photoconductive solid-state plasma technology for extremely low loss sub-THz phase shifting applications for future 6 G communication systems.