Design and Analysis of Potential Phased Array Configurations for Wideband Near-Field Beamforming

Near-field beamforming has similar challenges with beam squint like the typical far-field beamforming. This paper analyzes the spatial and frequency domain behaviors of a arc-shaped phased array with a corporate-fed and a series-fed feeding architecture. Both the configurations have the antennas placed in the geometric locus having a constant electrical length of the optical paths from the focal point in space to the power-combining node at the printed circuit board (PCB) through individual antenna elements. In this way, the signals from all the antennas will arrive in phase at the summing node in a given link condition. The impact of the dielectric constant of the PCB material is also considered. In the corporate-fed scheme, simulation results show that the array has a focal point whose position is independent from the frequency, due to the equalized delays of the phased array paths. Moreover, the frequency response in such a focal point is flat and the band is potentially not limited by beam squint. On the contrary, with a series-fed architecture, phase shifters can be added to compensate for the transmission line lengths among the antennas, at the cost of a reduced bandwidth, due to the angular-dependent squinting phenomenon. The paper reveals that the behavior of the beam squint phenomenon can be altered by geometric array configuration and feeding architecture in analog beamforming systems.