Design of High-Gain and High-Purity D-Band Orbital Angular Momentum Antenna Based on Cassegrain Sub-reflectarray Antenna

Vortex electromagnetic wave with high gain has excellent potential in terahertz communication systems. In this paper, a Cassegrain antenna that can generate a high-gain orbital angular momentum (OAM) mode-tunable beam is proposed in D-band. The antenna is composed of three parts, i.e., the linear polarized corrugated horn feed, paraboloid reflector, and sub-reflector composed of the metasurface. The OAM mode is tuned by adjusting the arrangement of elements in the sub-reflector. The simulation results show that the gains of different OAM beams at 150 GHz are more significant than 42.9 dBi while maintaining good mode purity of more than 95%, which can provide a good candidate for the combination of terahertz technology and OAM techniques in the coming 6G age.