Compact High Transmissivity Metal-Waveguide Mode Converters Based on Metasurface

This article presents a novel approach for achieving a compact high transmissivity mode converter (MC) using a metasurface-based mode converter (MMC). Specifically, the design of Ka-band MCs is proposed using this method, including TE $_{10}^{\mathrm {(R)}}$ –TE $_{20}^{\mathrm {(R)}}$ –TE $_{01}^{\mathrm {(C)}}$ (R denotes rectangular and C denotes circular, RC-MMC) and TE $_{10}^{\mathrm {(R)}}$ –TE $_{30}^{\mathrm {(R)}}$ (RR-MMC). The RC-MMC is designed in a transition metal waveguide with an alumina metasurface and a metallic resonant metasurface, while the RR-MMC is achieved using an alumina metasurface. The simulation results demonstrate that the S21 exhibits a loss less than 0.5 dB in the 1.2-GHz bandwidth for RC-MMC and 2.3-GHz bandwidth for RR-MMC, respectively. In addition, S21 can reach a maximum value of −0.1 dB. Finally, a TE $_{10}^{\mathrm {(R)}}$ –TE $_{20}^{\mathrm {(R)}}$ MMC is fabricated and tested. The experimental results show that the −3-dB bandwidth of this MMC is 2.39 GHz, and S11 is less than −16 dB. Using MMC instead of complex waveguide structures could pave the way for the miniaturization of MC for integration. This advancement could also extent to various applications, including the design of vacuum electronic devices and satellite-specific mode transmitters.