Flexible Multi-Beam Generation Based on 4-D Antenna Arrays with Low Hardware Complexity

High flexibility of beamforming has always been one of the major motivations for antenna array design. However, high flexibility always leads to complex and expensive feeding networks. Regarding this issue, this paper presents an effective multi-beamforming approach based on 4-D antenna arrays. In comparison to the traditional harmonic-based beamforming approach, this proposed approach can arbitrarily change the direction of multi-beams without a complex RF switch structure. By utilizing the design degrees of freedom in baseband, individually steerable multiple beams can be generated only with the simple on-off switches. The effectiveness of proposed approach is validated through theoretical analysis and numerical simulations.