Analog Beamforming based on Fourier Rotman Lens for Multibeam Applications

Spatial division represents a popular approach to increasing capacity in modern wireless networks. This paper presents a study of a simplified beamforming network based on a Fourier transform network with the number of output ports lower than the number of the elements in the antenna array. It is shown that connecting the output ports of Fourier transform network via power dividers to several array elements in phase, thus implementing a nearest-neighbor phase interpolation, preserves the gain and width of the beams in a narrow scanning sector. Therefore, in applications where few orthogonal beams are required to span a narrow spatial sector, the proposed approach can offer reduction of the hardware complexity. The simulated radiation patterns for a phase interpolation Fourier beamforming network are demonstrated. The antenna radiation patterns have been measured, using a Fourier Rotman lens with 2-way Wilkinson power dividers, which confirmed the simulated trends.