Wide-Angle Scanning Lens Fed by Small-Scale Antenna Array for 5G in Millimeter-Wave Band

This article aims at high-gain and wide-angle scanning lens antenna design in millimeter-wave (MMW) band. The proposed antenna consists of a novel gradient-index (GRIN) lens and a phased array antenna (PAA) feed with aperture-coupled microstrip antenna (ACMA) elements. A new design methodology of the GRIN lens antenna is proposed, which comprises a preliminary design for rough shapes of GRIN lenses and two successive optimization steps. In the first optimization step, parameters of the GRIN lens are determined to achieve high directivity and wide scanning angle based on particle swarm optimization (PSO) algorithm and a quasi-2-D model. In the second step, the excitation coefficients of all elements for beam-steering purpose are obtained by the PSO algorithm with the goal of maximum directivity. To validate the approach, an MMW lens antenna, operating at 28 GHz, is numerically demonstrated with high directivity and a wide scanning range up to ±58°. Finally, the proposed antenna is fabricated by 3-D printing techniques. The measured results are in acceptable agreement with simulations.