A compact reconfigurable feeding network for 5G quadri-polarization antennas

Abstract

This letter presents a compact reconfigurable feeding network, which can provide four polarizations. The feeding network includes a branch-line hybrid, two p-i-n diodes, and two grounded capacitors. By manipulating the on/off states of the two diodes, the capacitor can be selectively integrated into the hybrid circuit. Hence, the power distribution of the output ports is changed. The feeding network operating in state I provides a pair of orthogonal linear polarizations (LPs) when both diodes are turned off. The feeding network operating in state II provides a pair of orthogonal circular polarizations (CPs) when both diodes are turned on. Experimental results show that the proposed feeding network has a wide operating bandwidth from 3400 to 3800MHz with S₁₁≤-20dB and isolation level >20dB in two states. Moreover, the amplitude imbalance of the output ports is less than 1.3dB with a 90^° stable phase difference when the feeding network operates in state II. The presented reconfigurable feeding network is suitable for fifth-generation (5G) quadri-polarization antennas.