Ultra-Compact Electromagnetic Metamaterial Transmission Line and Its Application in Miniaturized Butler Matrix

Abstract

Abstract-A novel super compact electromagnetic metamaterial transmission line (EM-MTM TL) is proposed in this paper by using the structure of symmetric double spiral lines (SDSLs). The investigation results indicate that the proposed EM-MTM TL not only has controllable resonant frequency, but also has very compact size, and the circuit area is only 8.8 mm × 7.2 mm (equal to λ 0 /32.16 × λ 0 /39.31, where λ 0 is the free space wavelength at the resonant frequency) without the feed lines. Using the proposed structure, a 3-dB branch-line coupler and a 0-dB crossover operated at 0.86 GHz have been designed, fabricated and measured; the measured and simulated results are in good agreement. The two microwave devices realize 84.8% and 85.7% size reduction, respectively. Then, a compact Butler matrix is obtained by optimizing the combination of the branch-line couplers, 0 dB crossovers and 45-degree phase shifters. The measured and simulated results of the proposed Butler matrix agree well, showing that the proposed device operates at 0.86 GHz with very good electromagnetic performances. Moreover, the circuit area of the proposed Butler matrix is 109.0 mm × 89.3 mm, which realizes at least 80.9% size reduction in comparison with the conventional one (whose circuit area is at least 226.2 mm × 226.2 mm), and the miniaturization is considerable. Besides, these designed microwave devices, without any lumped elements, bonding wires, defected ground structure (DGS), and via-holes, are more suitable for modern wireless communication systems.

Butler Matrix Based Beamforming Networks for Phased Array Antenna Systems: A Comprehensive Review and Future Directions for 5G Applications

“…The analysis was done at different operating frequencies, bandwidth, performance parameters, and size reduction. From the summary, it was understood that the insertion-loss was always in the range of −7 ± 1dB, and the average phase-error of ±4 • for the frequency range of 0.8GHz to 28GHz as presented in [73]- [81]. This led to the understanding that the insertion-loss did not increase with respect to the change in the operating frequency.…”

“…In [73], symmetric double spiral-lines (SDSLs) structure was used to develop the novel electromagnetic (EM) MTM-TL (EM-MTM-TL). The proposed BM using EM-MTM-TL was operated at 0.86GHz.…”

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

“…The main beam of an antenna is steered by the BFN network with the given phase and amplitude. There are many different types of BFNs reported in the literature [9]- [14], [16]- [18], [22]- [27]. The BFNs have two categories 1) Rotman lens and 2) Circuit-based beamformer.…”

“…A novel compact BM without phase shifter is presented in [17] that contains couplers with −45 • and −90 • phase difference and a crossover. In [18], a novel electromagnetic metamaterial transmission-line (EM-MTM TL) is proposed by using the structure of symmetric double spiral lines (SDSLs). As per the literature review presented here, most of the discussed designs demonstrate a reduction in the area without much improvement in the bandwidth of the BM.…”

Miniaturisation of switched beam array antenna using phase delay properties of CSRR‐loaded transmission line

“…This method involves multi-layer configurations. A compact electromagnetic-MTM transmission line (EM-MTM TL)-loaded Butler matrix is proposed in [17] using the structure of symmetric double spiral lines. In all these cases, the LH media consists of complex configurations and are realised in the signal plane which are prone to interference.…”