Multifunction Pattern Reconfigurable Slot-Antenna for 5G Sub-6 GHz Small-Cell Base-Station Applications

Abstract

A new compact multifunctional pattern reconfigurable 2× 2 antenna array at 3.65 GHz with high gain and 16 (Multiple Input Multiple Output) MIMO modes is proposed. The single-element antenna includes 4 U-slots etched on the ground plane, with orthogonal slot orientations for polarization un-correlation, and fed using a reconfigurable feeding network with 4 PIN diodes. Hence, the single-element antenna is a pattern reconfigurable U-slot antenna with four pattern configurations. The average efficiency of 80%, the peak gain of 9.4 dB, and an overlapped -10 dB impedance-bandwidth of 200 MHz at a resonant frequency of 3.65 GHz in the n78 5G band are achieved. The single-element size is 55.5× 54 mm2, 0.66 λ 0 × 0.65 λ 0. The horizontal and vertical distances between the U-slots in a single-element are 30 mm (0.36λ 0) , and 27 mm (0.32λ0) , respectively. The 2× 2 antenna array of such an element with a 58.5 mm (0.7λ0) between the elements occupies a volume of 140× 140× 21 mm3. The 2× 2 elements provide 16 reconfigurable U-slots with two modes of operation, Array Mode and Multiple-Input-Multiple-Output (MIMO) Mode. For the MIMO Mode, the antenna has a maximum Envelope Correlation Coefficient (ECC) of 0.1194 between the radiation patterns and a minimum isolation of 20 dB between the four ports. For the array Mode, a 4× 4 antenna array has a peak gain of 17 dBi, and a beam-steering range of -50 ≤ θ ≤ 50 in the two principle planes. The antenna is suitable for small cell base-station applications.