Phase interpolation Fourier transform beamforming for spatial division applications

The spatial division represents an efficient approach to increasing data throughput in wireless networks. It can be implemented by spanning the channel in spatial domain with orthogonal beams generated by a Fourier transform (FT) beamforming network and using each beam to simultaneously convey an independent data stream from the base station (BS) to several users. This study presents a feasibility study of a simplified BS front-end architecture based on a spatial discrete FT beamforming network, with the number of the output ports being lower than the number of the elements in the antenna array. It is shown that connecting each output port of the FT network via power dividers to several array elements, thus implementing a 'sample-and-hold' phase interpolation, preserves the orthogonality, gain and beam-width 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 a reduction of the hardware complexity. The simulated radiation patterns for a phase interpolation Fourier beamforming network are demonstrated. The measured antenna radiation patterns are reported for the architecture implemented with a Fourier Rotman lens and Wilkinson power dividers feeding a microstrip antenna array, which confirm the simulated trends.