A Novel Metamaterial-Based Planar Integrated Luneburg Lens Antenna With Wide Bandwidth and High Gain

A novel metamaterial-based and broadband planar integrated Luneburg lens antenna is designed, fabricated, and measured. A substrate integrated waveguide (SIW) horn antenna is applied as the source to illuminate the operation of the Luneburg lens. In particular, air-via metamaterial structures are loaded in front of the SIW horn aperture to realize broadband performance. Meanwhile, the feeding structure by the SIW horn antenna and the Luneburg lens are integrated through this air-via metamaterial transition. Accordingly, the air-via unit cells are designed and arranged in an array with an equivalent gradient refractive index through diameters to achieve good wave focusing effects. Besides, a good agreement is observed between simulations and experiments. The measured results indicate that a wide bandwidth from 16 to 28 GHz is realized with the return loss below -10 dB. Moreover, high end-fire gains varying from 12.5 to 17 dBi are obtained in the band of 18-27 GHz.