(A) study on design of hybrid multibeamforming system and antenna 3D radiation pattern measurement system with a calibration technique

Abstract

As mobile communication systems move from 4G to the 5G/6G era, new antenna technologies are being developed. In 5G/6G, multiple-input and multiple-output (MIMO) technology using multiple antennas, which can prevent power loss in the air as frequency bands increase, is key. Representative technologies of MIMO include beamforming and multibeam. Beamforming enables flexible network configuration by controlling the angle of the antenna's main beam. Multibeam can secure wide beam coverage by transmitting/receiving multiple beams at the same time. Various antenna technologies that implement beamforming and multibeam are being developed, and a new antenna measurement system is required to determine the accurate performance of the antenna. In this paper, we conduct research on hybrid multibeamforming system technology for 5G/6G mobile communication and an antenna 3D radiation pattern measurement system with calibration technique. First, the architecture of hybrid multibeamforming system based on analog and digital beamforming system structure is described. The conventional hybrid beamforming system combines an RF-based analog and a baseband-based digital system structure. However, we propose a new hybrid multibeamforming system structure and construct analog and digital beams by performing analog and digital beamformers independently. The generated analog and digital beam can be used simultaneously or selectively. In addition, the angle of each beam can be individually controlled. As mobile communication frequency bands increase, the performance of RF modules becomes more sensitive to temperature. In particular, for antenna measurement systems in the millimeter-wave band, a calibration technique is essential to maintain the performance of measurement system in order to extract accurate antenna performance. In this paper, we introduce an antenna 3D radiation pattern measurement system with calibration technique. The antenna measurement system consists of a vector network analyzer and frequency extension modules capable of extracting real-time feedback signals. The proposed system with calibration technique was verified by analyzing the simulation and measurement results of the antenna radiation pattern. The antenna spacing of an array antenna is an important factor in determining the radiation pattern. If the distance between element antennas is more than half a wavelength, a grating lobe occurs. This may confuse in mobile communication because the grating lobe of the array factor of the array antenna has the same power as the main lobe. In this paper, in order to reduce the power of the grating lobes, the optimized spacing between array antenna is presented using the Markov Chain Monte Carlo algorithm. The performance of the proposed algorithm is verified by analyzing the radiation pattern of the array antenna.