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 0 and 0.36 0, where 0 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%.