A novel dual-linear polarized active aperiodic millimeter-wave (26 GHz band) phased array is prototyped. Four-channel integrated circuits are used for beamforming. An asymmetrical signal distribution and antenna feeding network is designed. A heuristic post-calibration method is applied in beam steering. The measurements show that, as compared to the benchmark array with a conventional square-grid layout, the proposed aperiodic topology can significantly decrease the peak sidelobe level, the extent of which depends on the polarization and scan angle. This comes at the expense of larger array size, higher feed network losses and increased cross-polarization levels.

@en

A heuristic calibration-before-operation method based on near-field-measurements of integrated circuit (IC) responses is proposed and tested for an active 64-element 5G millimeter-wave (24-28 GHz) phased array. The IC phase shifter and variable gain settings are digitally tuned to minimize the relative differences in complex transmission coefficients on broadside at each element. It is shown that, by means of calibration, it is possible to increase the array gain, decrease the peak side lobe level and remove the beam pointing errors.

@en

Heat removal capabilities and radiation performances of several sparse antenna array topologies are studied for cooling enhancement in 5G millimeter-wave base station antennas. Both electromagnetic and thermal aspects are jointly considered for the first time in array layout optimization and a novel connection between layout sparsity and thermal management is presented. Two types of active electronically scanned arrays (AESA’s), based on the traditional and planar approaches, are examined. Thermal management in AESA’s is discussed, with a focus on cooling challenges at millimeter waves. Being relatively low-cost and low-profile while supporting flexible beamforming, passively cooled planar AESA’s with fanless CPU coolers are proposed, for the first time, to be used in 5G base stations. Additional cooling for such arrays is achieved by increasing the inter-element distances in the layout. Linear irregular arrays, spiral arrays, thinned arrays, circular ring arrays and heat sink antenna arrays are revisited with a critical discussion on their electromagnetic and thermal performance. The results are compared with regular and square layouts that are used as benchmarks throughout the paper.@en