Compact Planar Beamforming Array With Endfire Radiating Elements for 5G Applications

Abstract

In this paper, a compact 4 × 6 Butler matrix (BM) based on microstrip lines is designed and applied to a linear antenna array. The proposed design creates four beams in four different directions within the 27.5 GHz and 28.5 GHz band. One of the advantages of this BM is a reduction in the size of the beamforming network (BFN). In order to attain this objective, the basic microstrip-based 4 × 4 BM is designed, and then modified to a 4 × 6 BM through a dual-substrate structure to avoid crossing lines using microstrip-to-slotline transitions. The BFN is cascaded with a 6-element linear antenna array with end-fire radiating elements. The array can be conveniently integrated into the BFN. The resulting design benefits from low loss characteristics, ease of realization, and low fabrication cost. The array is fabricated and tested, and the experimental results are in good agreement with the simulated ones. The multi-beam antenna size is 5.6λ×4.6λ including feed lines and feed network, while the new BM design is only 3.5λ0 × 1.4λ0, which is almost half as large as the traditional one. The measured radiation patterns show that the beams cover roughly a spatial range of 90 • with a peak active gain of 11 dBi.

Connecting Networks for Two-Dimensional Butler Matrices Generating a Triangular Lattice of Beams

“…In recent years, there have been various developments reported on multiple beam antennas and associated beamforming techniques, driven by the specific needs of 5G terrestrial networks as well as small-space platforms for low Earth orbit (LEO) satellite constellations. This includes advances on beam forming networks (BFN), such as Blass [1], [2], Butler [3]- [5] and Nolen matrices [6]- [8], as well as parallel plate waveguide quasi-optical beamformers [9]- [14]. When a small number of beams is required (typically a few tens of beams), BFNs are generally preferred, and in particular Butler matrices in waveguide technology, as they provide low insertion losses and higher integration in the millimeter-wave band.…”

Circuit Type Multiple Beamforming Networks for Antenna Arrays in 5G and 6G Terrestrial and Non-Terrestrial Networks

“…Ansari et al [60] presented a microstrip-to-slot line transition to avoid the use of excessive crossovers in Butler matrices with a larger number of outputs. Their proposed structure is operating at 28 GHz with a size of 3.5λ × 1.5λ, which is only 50% of the area that an equivalent conventional matrix would occupy.…”

“…Various realization techniques and associated transmission line technologies have been reported for the fabrication of circuit type multiple BFNs. These include microstrips [16], [56], [60], [119], striplines [101], low-temperature cofired ceramic [120], ridged-waveguides [73], hollow waveguide [121], SIW [53], [115], [122], half-mode SIW [123], ridged half-mode SIW (RHMSIW) [44], coplanar waveguie (CPW) [85], to list a few examples.…”

An Elliptical Cylindrical Shaped Transmitarray for Wide-Angle Multibeam Applications

“…Compared with the existing 5G digital/hybrid beamforming technologies [2][3], passive or analogue multibeam antennas offer several significant commercial advantages, including lower manufacturing costs, reduced power consumptions and more deployment flexibilities. The existing passive multibeam antennas include those based on lens [4][5][6], transmitarrays [7][8][9], reflectarrays [10][11][12] and beamforming circuits, e.g., Butler-matrix-based antennas [13][14]. Among them, transmitarrays/reflectarrays have their own merits of achieving high gains without needing lossy transmissionline-based feeding networks.…”