2-D Deformed Half Fisheye Lens as Beamforming Network to Excite Planar Arrays of Antennas for Multibeam Radiations

Multibeam (MB) radiations of antenna arrays rely on effective beamforming networks (BFNs). A 2-D fisheye lens-based BFN (FL-BFN) was developed using a half 2-D lens realizable on metal parallel-plate sandwiched substrates to excite a planar antenna array. This FL-BFN implemented the beam and antenna excitation ports on its half-circular circumference and straight boundaries. An optimization scheme was developed to minimize the ray propagation distortion due to an incomplete half-lens propagation path for an offset beam, which results in an aperiodic array of antennas for MB radiations. Excitations for periodic arrays can also be implemented by considering an aperiodic output port establishment. The rule to determine the positions of antenna elements is also shown for easy design. This FL-BFN performance is demonstrated using its output amplitudes and phases to excite a Vivaldi antenna array for MB radiation. Numerical simulations and measurements over a prototype were performed to validate its feasibility with distinguished agreements.