Wideband sub-Terahertz Horn Antenna with Parasitic Dipole for Metasurface Feeding Network

In the sub-Terahertz (sub-THz) spectrum, high-frequency horn antennas face stringent design constraints, including microscale fabrication challenges, wide bandwidth requirements, and symmetric radiation for advanced applications like metasurface feeding. This communication presents a novel horn antenna featuring a parasitic dipole integrated with a compact conical horn, innovatively addressing these constraints. The dipole, inspired by the complementary antenna concept, ensures axially symmetric amplitude and phase distributions, achieving symmetric E-/H-plane patterns critical for metasurface feeds. Unlike complex ridged or corrugated horns, the proposed design leverages simple CNC fabrication, mitigating sub-THz manufacturing difficulties while maintaining a compact form. Simulated and measured results show excellent agreement, with measured gain ranging from 11 to 14 dBi, wide 43.48% impedance bandwidth, low back radiation of -30 dB, and low cross-polarization of -40 dB. The proposed design offers a unique combination of bandwidth, symmetry, and fabrication simplicity that outperforms traditional high-frequency horns, showing significant potential for metasurface-based sub-THz applications.