Compact waveguide-integrated metasurface twist with filtering and phase shifting capabilities for millimeter-wave...

Recent advancements in metasurfaces have enabled precise control of wave properties such as amplitude, phase, and polarization, which are critical for multifunctional devices in modern communications. While most metasurfaces are designed for free-space use, this work integrates metasurfaces within waveguides to enable guided-wave control. We introduce a compact waveguide-integrated metasurface twist that achieves polarization rotation, bandpass filtering, and phase shifting. The metasurface comprises a $3\times 3$ array of dog bone-shaped resonators and orthogonal gratings. Positioned between two rectangular waveguides with a $90°$ twist, it allows precise tuning of wave properties. A fabricated prototype operating in the 26.6-29 GHz band shows an average insertion loss of 0.6 dB and a minimum of 0.34 dB at 28 GHz. This work demonstrates a compact, high-performance solution for millimeter-wave (mm-wave) guided-wave systems with a device thickness of only $0.16{\lambda }_g$ .