Recent Developments of Butler Matrix From Components Design Evolution to System Integration for 5G Beamforming Applications: A Survey

Abstract

Beamforming networks for multiple beam antennas are believed to be in the vanguard of technological developments in mmWave for 5G wireless applications. The basic idea of beamforming technique is the application of multiple antenna elements radiating the same signal at an identical phase and wavelength, into one strong signal pointed to a specific direction. For low cost and power consumption, radio frequency beamforming networks (RF-BFNs) such as Blass matrices, Butler matrices, and Nolen matrices will play a critical role in achieving the ever-increasing demands in wireless technology. Therefore, this study aims to present a comprehensive survey and developments of RF-BFNs with (particular focus in Butler matrices). From the fundamental perspectives of the beamforming techniques and progress over time, component evolution includes branch-line coupler (BLC), Phase shifter (PS), and Crossovers to complete system Butler matrix (BM) integration. Different design techniques to improve bandwidth, size reduction, multi-band, and other performance characteristics are discussed extensively. Furthermore, the paper also discusses different geometry of Butler matrices in open microstrip transmission lines, substrate integrated waveguide (SIW) and gap waveguide (GWG) technologies highlighting key developments and research challenges from single band to dual-band operations. We expect this paper to provide more profound insights into the designs processes and suggest suitable ways to facilitate further developments of RF-beamforming networks at mmWave and sub-mmWave frequency ranges.INDEX TERMS Beamforming networks (BFNs), Butler matrix (BM), fifth-generation (5G), metamaterial (MTM), millimetre-waves (mmWave), substrate integrated waveguide (SIW), gap waveguide (GWG), ridge gap waveguide (RGW), groove gap waveguide (GGW).

A Miniaturized Multi-Beam Wideband High Gain-5G Antenna Based on a Novel Design of Compact 4x4 Butler Matrix

“…However, fully harnessing this potential necessitates the creation of efficient and compact antenna systems. Because of their ability to produce beamforming, the pairing of a Butler Matrix network with linear array antennas has attracted a lot of interest, holding the promise of significantly improving the performance of wireless communication systems [22]. The integration of these two components offers the prospect of an advanced antenna system that amalgamates the beamforming prowess of a Butler Matrix with the high gain and directivity inherent to a linear array antenna.…”

1.58 Tbps OAM Multiplexing Wireless Transmission With Wideband Butler Matrix for Sub-THz Band

“…A Butler matrix is an analog beamforming circuit for multibeam antenna technologies [24]. A block diagram of an 8×8 Butler matrix circuit is shown in Fig.…”

“…Unlike other methods, the use of UCAs does not require coaxial beam synthesis using a beam combiner or similar device and enables simultaneous generation of OAM beams with a simple antenna configuration, so we consider it practical and suitable for radio communications. When using UCAs, the beamforming process is also fixed, i.e., discrete Fourier transform (DFT), and an analog circuit called a Butler matrix can be used [24]. There have been numerous reports on the design and implementation of Butler matrices in the field of analog beamforming technology [25] not only for OAM multiplexing [26].…”

Design and Implementation of C-Band Large-Power Planar Butler Matrix in SRS

“…The beamforming networks are an essential part of an SRS transmitting antenna array. There are many beamforming networks reported [1], like the Rotman lens, Blass matrix, Nolan matrix [2], and Butler matrix [3][4][5]. Compared with these passive beamforming networks, the Butler matrix is the most popular choice, given its more straightforward and cost-effective structure and wider bandwidth [6].…”