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

A new compact multifunctional pattern reconfigurable 2 x 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 uncorrelation, 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 x 54 mm(2), 0.66 lambda 0x0.65 lambda 0. The horizontal and vertical distances between the U-slots in a single-element are 30 mm (0.36 lambda 0), and 27 mm (0.32 lambda 0), respectively. The 2 x 2 antenna array of such an element with a 58.5 mm (0.7 lambda 0) between the elements occupies a volume of 140 x 140 x 21 mm3. The 2 x 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 4x4 antenna array has a peak gain of 17 dBi, and a beam-steering range of -50 degrees <= theta <= 50 degrees in the two principle planes. The antenna is suitable for small cell base-station applications.