Low-Profile High-Gain Slot Antenna Using Polarization- and Incident-Angle-Insensitive Metamaterial

This paper presents a novel metamaterial (MTM) which exhibits negative permittivity in a wide band of frequency and epsilon-very-large (EVL) mu-near-zero (MNZ) properties at around the frequency of 8.2 GHz irrespective of polarization and incident angles of the incident electromagnetic (EM) wave. The proposed MTM shows a low-impedance property in a wide band of frequency, i.e., Re(ηr) < 0.01 in 8.2–15.1 GHz and Im(ηr) < 0.5 in 8.2–10.6 GHz. The design of a low-profile high-gain substrate-integrated waveguide (SIW) cavity-backed slot antenna operating in the frequency band of 8.08–8.33 GHz is achieved by using the MTM in the superstrate. The peak realized gain of the proposed antenna is 8.22 dBi, which is 96.5% of the maximum attainable gain obtained from the Harrington limit. The simulated radiation efficiency and the broadside realized gain of the proposed antenna are greater than 93% and 7.7 dBi, respectively, throughout the entire operating frequency band. The superstrate height and the overall antenna profile are 2.5 mm and 4.1 mm, i.e., 0.067 λ0 and 0.11 λ0, respectively, at the lowest operating frequency of the antenna. This antenna can be used for line-of-sight (LoS) communications, wireless energy transfer, etc.