scholarly journals Realization of frequency hopping characteristics of an epsilon negative metamaterial with high effective medium ratio for multiband microwave applications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammad Tariqul Islam ◽  
Md. Moniruzzaman ◽  
Touhidul Alam ◽  
Md Samsuzzaman ◽  
Qutaiba A. Razouqi ◽  
...  
Keyword(s):  
Refractive Index ◽  
Low Cost ◽  
Frequency Hopping ◽  
Small Dimension ◽  
Effective Medium ◽  
Unit Cell ◽  
Negative Permittivity ◽  
Design System ◽  
Microwave Applications ◽  
Meander Line

AbstractIn this paper, a meander-lines-based epsilon negative (ENG) metamaterial (MTM) with a high effective medium ratio (EMR) and near-zero refractive index (NZI) is designed and investigated for multiband microwave applications. The metamaterial unit cell is a modification of the conventional square split-ring resonator in which the meander line concept is utilized. The meander line helps to increase the electrical length of the rings and provides strong multiple resonances within a small dimension. The unit cell of proposed MTM is initiated on a low-cost FR4 substrate of 1.5 mm thick and electrical dimension of 0.06λ × 0.06λ, where wavelength, λ is calculated at the lowest resonance frequency (2.48 GHz). The MTM provides four major resonances of transmission coefficient (S21) at 2.48, 4.28, 9.36, and 13.7 GHz covering S, C, X, and Ku bands. It shows negative permittivity, near-zero permeability, and near-zero refractive index in the vicinity of these resonances. The equivalent circuit is designed and modeled in Advanced Design System (ADS) software. The simulated S21 of the MTM unit cell is compared with the measured one and both show close similarity. The array performance of the MTM is also evaluated by using 2 × 2, 4 × 4, and 8 × 8 arrays that show close resemblance with the unit cell. The MTM offers a high effective medium ratio (EMR) of 15.1, indicating the design's compactness. The frequency hopping characteristics of the proposed MTM is investigated by open and short-circuited the three outer rings split gaps by using three switches. Eight different combinations of the switching states provide eight different sets of multiband resonances within 2–18 GHz; those give the flexibility of using the proposed MTM operating in various frequency bands. For its small dimension, NZI, high EMR, and frequency hopping characteristics through switching, this metamaterial can be utilized for multiband microwave applications, especially to enhance the gain of multiband antennas.

scholarly journals Tailoring exceptional points in a hybrid PT-symmetric and anti-PT-symmetric scattering system

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Zhicheng Xiao ◽  
Andrea Alù
Keyword(s):  
High Resolution ◽  
Real Time ◽  
Quantum Systems ◽  
Symmetric System ◽  
Microwave Circuit ◽  
High Resolution Imaging ◽  
Fano Resonances ◽  
Real Time Control ◽  
Time Control ◽  
Resolution Imaging

Abstract Fano resonances feature an asymmetric lineshape with controllable linewidth, stemming from the interplay between bright and dark resonances. They provide efficient opportunities to shape the scattering lineshape, but they usually lack flexibility and tunability and are hindered by loss in passive systems. Here, we explore a hybrid parity-time (PT) and anti-parity-time (APT) symmetric system supporting unitary scattering features with highly tunable Fano resonances. The PT-APT-symmetric system can be envisioned in nanophotonic and microwave circuit implementations, allowing for real-time control of the scattering lineshape and its underlying singularities. Our study shows the opportunities enabled by non-Hermitian platforms to control scattering lineshapes for a plethora of photonic, electronic, and quantum systems, with potential for high-resolution imaging, switching, sensing, and multiplexing.

scholarly journals Enabling propagation of anisotropic polaritons along forbidden directions via a topological transition

2021 ◽  
Vol 7 (14) ◽  
pp. eabf2690
Author(s):  
J. Duan ◽  
G. Álvarez-Pérez ◽  
K. V. Voronin ◽  
I. Prieto ◽  
J. Taboada-Gutiérrez ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Silicon Carbide ◽  
Molybdenum Trioxide ◽  
Real Space ◽  
Negative Permittivity ◽  
Topological Transition ◽  
Α Phase ◽  
Direct Light ◽  
Gap Opening ◽  
Phonon Polaritons

Polaritons with directional in-plane propagation and ultralow losses in van der Waals (vdW) crystals promise unprecedented manipulation of light at the nanoscale. However, these polaritons present a crucial limitation: their directional propagation is intrinsically determined by the crystal structure of the host material, imposing forbidden directions of propagation. Here, we demonstrate that directional polaritons (in-plane hyperbolic phonon polaritons) in a vdW crystal (α-phase molybdenum trioxide) can be directed along forbidden directions by inducing an optical topological transition, which emerges when the slab is placed on a substrate with a given negative permittivity (4H–silicon carbide). By visualizing the transition in real space, we observe exotic polaritonic states between mutually orthogonal hyperbolic regimes, which unveil the topological origin of the transition: a gap opening in the dispersion. This work provides insights into optical topological transitions in vdW crystals, which introduce a route to direct light at the nanoscale.

The negative permittivity behavior and magnetic property of FeNi/Al2O3 composites in radio frequency region

2016 ◽  
Vol 42 (16) ◽  
pp. 19063-19065 ◽  
Author(s):  
Zidong Zhang ◽  
Kai Sun ◽  
Yao Liu ◽  
Zhaoyu Kuang ◽  
Suyang Sun ◽  
...  
Keyword(s):  
Magnetic Property ◽  
Radio Frequency ◽  
Frequency Region ◽  
Negative Permittivity
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