Passive Beam Switching and Dual-Beam Radiation Slot Antenna Loaded With ENZ Medium and Excited Through Ridge Gap Waveguide at Millimeter-Waves
A unique antenna design is presented to implement the dual-beam radiation simultaneously in both $H$ - and $E$ -planes for operation over 57–64 GHz. The slot antenna is excited through a ridge gap waveguide. The dual beam is realized by employing arrays of anisotropic epsilon-near-zero (ENZ) structures that are located vertically over the slot antenna. The proposed ENZ medium behaves analogously to a meta-lens, and consists of meander-line H-shaped unit cells printed on the host substrate with a permittivity of 2.2. Measured results confirm that the dual-beam radiation from the antenna has maxima at ±30° with respect to the broadside direction with a maximum gain of 10 dBi at 60 GHz.