Compact Metamaterial Based $4\times4$ Butler Matrix With Improved Bandwidth for 5G Applications

Abstract

This paper proposes a novel compact 4 × 4 butler matrix (BM) with improved bandwidth based on open-circuit coupled-lines and interdigital capacitor unit-cell to develop composite right/left handed (CRLH) transmission-line (TL) metamaterial structure. The BM is implemented by the combination of compact 3dB quadrature hybrid couplers, 0dB crossover and 45 • phase shifter on a single FR4 substrate (ε r = 4.3 and h = 1.66 mm). The simulated and measured result shows that the return loss and isolation loss are better than 14 dB at all the ports, good insertion loss of −7 ± 2dB, which cover the frequency range of 3.2 GHz to 3.75 GHz. The phase difference of −45 • , 135 • , −135 • and +45 • are achieved with a maximum average phase tolerance of 5 •. The overall dimension of the BM is 70mm × 73.7mm, which shows the compactness of the proposed design that is 75% size reduction and 8.2 times improvement in the bandwidth (550MHz) as compared to conventional BM. The CST microwave studio is used to design and perform the simulations. Additionally, the simulated and measured scattering parameters and phase differences show that they are in good agreement. This compact and improved bandwidth of the proposed BM is suitable for 5G antenna array beamforming network. INDEX TERMS 5G, composite right/left handed (CRLH) transmission-line, metamaterial, beamforming network (BFN), Butler matrix (BM), branch line coupler (BLC).

Wideband 4×4 Nolen Matrix with 360° Continuously Tuned Differential Phase and Low In-Band Phase Deviation Error

“…Here, the phase slope at port 8 is served as a reference. According to (15), the circuit parameters in C-PS3 are obtained as follows: θ open = 62 3 °, Z open = 63 6 Ω, and Z 1 = 53 9 Ω. Obviously, according to the solid line in Figure 5, after compensation using C-PS3, the PD between ports 7 and 8 is flatted and the relative bandwidth for ±10 °error is increased to be more than 25%.…”

“…Equation ( 16) expresses the phase-frequency relationship of a 360 °line. By equaling (15) with ( 16), the parameters in the 180 °F-PS are obtained.…”

“…In the past decades, most of the Butler and Nolen matrices show narrow bandwidths, which is unfit for 5G applications. Although the BFNs in [6][7][8][9][10][11][12][13][14][15] exhibit enough bandwidth of impedance matching, the bandwidths for 1 dB output port amplitude imbalance and 10 °output port phase differences (PDs) are limited (<5%). It is noted that the evaluation of wideband application should be the overlapped bandwidth, which generally includes 10 dB impedance matching, 10 dB isolation, 1 dB output port amplitude imbalance, and 10 °output port phase differences.…”

A Miniaturized Metamaterial-Based Dual-Band 4×4 Butler Matrix With Enhanced Frequency Ratio for Sub-6 GHz 5G Applications

“…The application of MTM-TL to the BM network is relatively simple, and its performance remains unaffected even when the order is increased to 8×8 or beyond. This is because the MTM-TL properties were introduced without modifying the traditional BM layout [22].…”

Generalized Concept and MATLAB Code for Modeling and Analyzing Wideband 90° Stub-Loaded Phase Shifters with Simulation and Experimental Verifications

“…90° microwave phase shifters are devices that are widely used in variety of industrial applications. These phase shifters are commonly used in 5G and 6G beamforming systems [ 1 , 2 , 3 , 4 ]. The 90° phase shifters are also indispensable in exciting narrowband circularly polarized antennas [ 5 ] and broadband circularly polarized antennas [ 6 , 7 ].…”