This paper presents a 5G downlink system model for a hybrid multi-user beamforming technique at the base station. The presented technique employs power flux equalization in the elevation plane using a fixed analog cosecant-shaped beam and digital beamforming in the azimuth plane. The system performances of various beamforming algorithms are investigated via Monte-Carlo simulations by creating simultaneous co-frequency beams towards the randomly-located users. The simulation results show that the proposed cosecant subarray hybrid beamforming statistically performs better than the state-of-the-art hybrid beamforming techniques and provides reduced complexity.

Minimization of the maximum sidelobe level for a given array geometry, amplitude distribution, and nulling sectors by phase-only adjustment of the element coefficients is studied. Nonlinear optimization problem for phase distribution is solved using a novel iterative convex optimization algorithm, which includes mutual coupling effects and exploits small phase perturbations at each step. Superiority of the algorithm in terms of the peak sidelobe level and nulling depth achieved over several optimization methods reported in the most relevant literature is demonstrated in several case studies. Finally, a case study is performed to demonstrate added value of the algorithm for millimeter-wave fifth generation application with phase-only radiation pattern forming.

A planar tri-band rectangle-rings microstrip antenna design is presented in this paper. The antenna has three equally tuned resonant bands and also maintains consistent radiation patterns in all the operational sub-bands. The antenna has a single port and its cavity-backed waveguide-like configuration results in minimum mutual coupling levels in antenna array configuration. The antenna element is tuned to operate over the L/S/C radar bands. The antenna is simple and compact structure and measures only 0.25lambda × 0.25lambda at the lowest frequency of operation. Due to its small dimensions, the element is well-suited for application to dense wide-scan phased arrays.

A novel two-port, dual-band square-ring microstrip antenna element for wide-angle scanning planar phased array is proposed. The two ports are used to operate the antenna array over the L and S radar bands. Microstrip square-ring radiators are chosen due to their smaller dimensions compared to the conventional microstrip patch. To extend operational bandwidth, the square rings placed into a single layer are fed by small coupling patches. The antenna elements demonstrate consistent radiation patterns and sufficient bandwidths in both operational bands. Due to its dimensions, the element is well-suited for application to wide-scan phased arrays.