Abstract
To support the ever-increasing demand on connectivity and datarates, multiple beam antennas are identified as a critical technology for the fifth generation (5G), the sixth generation (6G) and more generally beyond 5G (B5G) wireless communication links in both terrestrial networks (TNs) and non-terrestrial networks (NTNs). To reduce the cost and power consumption, there is a marked industrial interest in adopting analogue multiple beam antenna array technology. A key sub-system in many of such antenna arrays is the circuit type multiple beamforming network (BFN). This has led to a significantly renewed interest in and new technological developments of Butler matrices, Blass matrices, and Nolen matrices as well as hybrid structures, mostly at millimeter-wave frequencies. To the best of the authors' knowledge, no comprehensive analysis and comparison of circuit type multiple BFNs have been properly reported with focus on 5 G and 6 G applications to date. In this paper, the principle of operation, design, and implementation of different circuit type multiple BFNs are discussed and compared. The suitability of these sub-systems for 5 G and B5G antenna arrays is reviewed. Major technology and research challenges are highlighted. It is expected that this review paper will facilitate further innovation and developments in this important field.
Highlights
The global deployment of the fifth generation (5G) of wireless and mobile communication systems is accelerating, and the technical race on the sixth generation (6G) has started in earnest in many parts of the world [1], [2]. 5G promises significantly increased capacity, massive connectivity, low latency, and game-changing new applications [3]. 6G is expected to provide much greater coverage, significantly reduced cost and energy consumption, and higher intelligence empowered by machine learning technologies [4]
To support the ever-increasing demand on connectivity and datarates, multiple beam antennas are identified as a critical technology for the fifth generation (5G), the sixth generation (6G) and more generally beyond 5G (B5G) wireless communication links in both terrestrial networks (TNs) and non-terrestrial networks (NTNs)
This paper provides a comprehensive review of various circuit type beamforming network (BFN)
Summary
The global deployment of the fifth generation (5G) of wireless and mobile communication systems is accelerating, and the technical race on the sixth generation (6G) has started in earnest in many parts of the world [1], [2]. 5G promises significantly increased capacity, massive connectivity, low latency, and game-changing new applications [3]. 6G is expected to provide much greater coverage, significantly reduced cost and energy consumption, and higher intelligence empowered by machine learning technologies [4]. A cost and energy efficient solution well fitting the microwave domain is analogue multiple beam antenna arrays based on circuit type beamforming networks (BFN). Such BFNs typically consist of fundamental microwave/millimeter-wave (mm-wave) circuit components such as power dividers, couplers, crossovers, phase shifters and switches. A circuit type BFN is fully characterized by its reduced scattering matrix, S, with dimensions N × M and containing the array coefficients in transmit, such that b = S a, where a and b are the network input and output complex amplitude vectors of dimension M and N, respectively. The main circuit type BFNs are detailed
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