Performance of Adaptive Beamforming with Multiport Parasitic Array Radiator Antenna

Modern wireless communications systems require improvement in capacity and data transmission speed. Adaptive array antennas separate spatially a desired wave from interference waves by controlling their radiation or beam pattern directivity. A digital beamforming (DBF) array performs adaptive beamforming by digital signal processing. However, the circuit scale, number of RF channels and power consumption increase with the number of array elements. In this paper, we propose a system of adaptive beamforming with multiport parasitic array radiator (MuPAR) antenna [1]. We apply the combination of a DBF and an analog beamforming algorithms at the MuPAR. The MuPAR consists of multiple active elements and parasitic elements. The parasitic elements are loaded with variable reactors. Since these elements are placed near the active elements, there is inducing strong electromagnetic coupling between parasitic and active ones. These parasitic elements operate as directors or reflectors by adjusting reactance of variable reactors. Compared with a DBF array having the same number of elements, the MuPAR structure is composed of less RF channels and A/D converters, thus has less power consumption. The goal of this paper is to examine the performance of adaptive beamforming with the MuPAR. We apply the steepest gradient algorithm (SGA) [2] to optimize the reactances; and apply RLS algorithm [3] to perform DBF at the active elements. We compare adaptive beamforming performance with DBF array.