Fully Metallic Gradient Index Lens Array Antenna for Wide-Angle Scanning Phased Array

A phased array antenna (PAA) with wide beam scanning range (BSR) composed of fully metallic lens antenna subarrays is proposed. Each subarray is designed based on a partial Maxwell fish-eye (PMFE) lens, which provides a linear quasi-focal line and wide-angle beam scanning, which is achieved by the combination of the passive beam switching and the phase shifting control. The fully metallic PMFE lenses are realized by the parallel plate waveguides (PPWs) loaded with nonuniform nails. To meet the requirement of the subarray spacing, the miniaturization of the lens element and the staggering arrangement are implemented. In the prototype, the double-ridged feeding waveguide is employed, and the microstrip feeding networks are introduced to test the beam scanning performance. Besides, a transition between the feeder and the microstrip network is designed. The prototype is experimentally verified in 28-GHz band. The proposed lens array antenna yields a BSR of ±65.5° and a 3-dB beamwidth coverage range (BCR) of ±70.8°. The sidelobe levels (SLLs) below-8.0 dB and the maximum gain of 20.3 dBi are realized with the scan loss of 5.6 dB. The results indicate that the proposed lens array antenna has application potential in millimeter-wave (mmW) multibeam systems.