A 4 × 4 Millimeterwave-Frequency Butler Matrix in Grounded Co-Planar Waveguide Technology for Compact Integration With 5G Antenna Arrays

Abstract

This article presents a novel 4 × 4 Butler matrix implemented in the grounded co-planar waveguide (GCPW) technology, compactly integrated with a highly efficient and broadband 1 × 4 air-filled substrate integrated waveguide (AFSIW) cavity-backed patch antenna array (AA), giving rise to a broad operational frequency range [23.75, 31 GHz] (26.5%) covering the n257, n258, and n261 fifth-generation (5G) bands. Three novel quadrature hybrid couplers and two crossovers are designed and compared to obtain the optimal building blocks for the Butler matrix. Within each of the supported 5G bands, the measured excess insertion loss of the optimized Butler matrix remains smaller than 3.5 dB with a maximal amplitude imbalance of ±0.9 dB. Isolation between input ports is higher than 16.4 dB. A maximal measured realized gain of 12.3 dBi is obtained for the Butler matrix with integrated 1 × 4 AA while ensuring a −3-dB beamwidth coverage of 110 • . The main beamsteering directions of [−40 • , −14 • , 14 • , 40 • ] exhibit measured deviations that stay within ±3 • . The fabricated Butler matrix with AA features a very compact footprint of 21.4 mm × 46.0 mm × 2 mm [2λ 0 × 4.3λ 0 × 0.2λ 0 ].

System-Level Model for mmWave-over-Fiber Distributed Antenna Systems

“…This does not only allow for a thorough understanding of the link at each of its different stages, it also enables optimization of the link without setting up a complete mmWave-over-fiber distributed antenna system. During the conference, the different stages of the proposed model will be discussed in more detail and the versatility of the model will be showcased by using it in combination with a Butler-Matrix-based multi-beam remote antenna unit [9], [10].…”

System-Level Simulation Suite for the Design of mmWave-Over-Fiber-Based Distributed Antenna Systems

“…Owing to the mmWave-over-fiber scheme, the RAUs exhibit low hardware complexity and low power consumption. Therefore, they are highly cost-effective when compared to RAUs tailored towards other optical signal distribution techniques, such as DRoF and IFoF [23] for integration within a RAU [22], [24], [25]. Additionally, since the broadband RF signals are optically distributed to the RAUs, the mmWave-over-fiber architecture facilitates the application of optical beamforming networks, offering significant advantages over classical electronic beamforming in terms of insertion loss, bandwidth and EMI-immunity [25], [26] at the expense of more O/E and E/O transducers.…”

“…This paper now describes the simulation suite (architecture, inputs/outputs, interfaces) in more detail, and extends the conference contribution to multi-beam multi-user support. Moreover, to validate the simulation suite and prove its versatility, a wide range of measurement scenarios is analyzed, including uplink communication, different wireless channels, and an alternative RAU configuration with local beamforming [22].…”

Compact, Ultra-Wideband Butler Matrix Beamformers for the Advanced 5G Band FR3 – Part I

“…The recent advancements in 4×4 BM are summarized in Table 1 and those of 8×8 BM are depicted in Table 2. These approaches are grouped into single-layer (SL) [13][14][15][16][17][18][19] and multilayer (ML) [20][21][22][23][24][25][26][27][28][29] configurations. In [13,14] artificial transmission line branch line coupler (BLC) and swapped ports coupled line coupler, respectively, are utilized to achieve a reduction in the size of the BM from 21% to 10% (0.11λ 2 -0.05 λ 2 ) when compared to the conventional BM, while maintaining a fractional bandwidth (FBW) of 30%.…”

“…λ . An increase in the FBW to 26.5% is reported in [22], adopting the grounded coplanar waveguide (GCPW) technology. Using bent hybrid couplers, curved line phase shifter and multilayer transitioned crossovers, a size with FA of 5.04 2 0 λ is obtained.…”