A Compact Gradient Refractive Index Metamaterial Lens for End-Fire Fan-Beam Radiation

This letter presents an end-fire fan-beam radiation antenna by utilizing a gradient refractive index metamaterial lens. The lens includes one core and two impedance matching layers which are both based on the proposed metamaterial unit cells with a large refractive index variation range. An incident wave is excited from the antenna source and propagates to the lateral side of the lens. Two parallel plates set for the TE₁ mode condition are utilized such that E-plane radiating beam can be controlled. To validate our proposed design, a prototype working at 10 GHz is fabricated and measured. Measured results are in good agreement with the simulation. The height and thickness of the metamaterial lens are about 0.44 λ₀ and 0.36 λ₀, where λ₀ is the wavelength of the center frequency in free space. The measured E- and H- planes 3 dB beamwidths are 25º and 82º at the center frequency, respectively. The measured peak gain of the antenna is about 11.1 dBi, which implies a 5.4 dB gain enhancement compared with initial radiation source. Furthermore, this lens offers a high aperture efficiency of 72.4%.