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

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 mm 2 , 0.66λ 0 ×0.65λ 0 . The horizontal and vertical distances between the U-slots in a single-element are 30 mm (0.36λ 0 ), and 27 mm (0.32λ 0 ), respectively. The 2 × 2 antenna array of such an element with a 58.5 mm (0.7λ 0 ) between the elements occupies a volume of 140×140×21 mm 3 . 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.