2D MXene Ti3C2Tx Enhanced Plasmonic Absorption in Metasurface for Terahertz Shielding

With the advancement of technology, shielding for terahertz (THz) electronic and communication equipment is increasingly important. The metamaterial absorption technique is mostly used to shield electromagnetic interference (EMI) in THz sensing technologies. The most widely used THz metamaterial absorbers suffer from their narrowband properties and the involvement of complex fabrication techniques. Materials with multifunctional properties, such as adjustable conductivity, broad bandwidth, high flexibility, and robustness, are driving future development to meet THz shielding applications. In this article, a theoretical simulation approach based on finite difference time domain (FDTD) is utilized to study the absorption and shielding characteristics of a two-dimensional (2D) MXene Ti3C2Tx metasurface absorber in the THz band. The proposed metamaterial structure is made up of a square-shaped array of MXene that is 50 nm thick and is placed on top of a silicon substrate. The bottom surface of the silicon is metalized with gold to reduce the transmission and ultimately enhance the absorption at 1–3 THz. The symmetric adjacent space between the MXene array results in a widening of bandwidth. The proposed metasurface achieves 96% absorption under normal illumination of the incident source and acquires an average of 25 dB shielding at 1 THz bandwidth, with the peak shielding reaching 65 dB. The results show that 2D MXene-based stacked metasurfaces can be proven in the realization of low-cost devices for THz shielding and sensing applications

Expedited Yield Optimization of Narrow- and Multi-Band Antennas Using Performance-Driven Surrogates

Publisher's version (útgefin grein)Uncertainty quantification is an important aspect of engineering design, also pertaining to the development and performance evaluation of antenna systems. Manufacturing tolerances as well as other types of uncertainties, related to material parameters (e.g., substrate permittivity) or operating conditions (e.g., bending) may affect the antenna characteristics. In the case of narrow- or multi-band antennas, this usually leads to frequency shifts of the operating bands. Quantifying these effects is imperative to adequately assess the design quality, either in terms of the statistical moments of the performance parameters or the yield. Reducing the antenna sensitivity to parameter deviations is even more essential when increasing the probability of the system satisfying the prescribed requirements is of concern. The prerequisite of such procedures is statistical analysis, normally carried out at the level of full-wave electromagnetic (EM) analysis. While necessary to ensure reliability, it entails considerable computational expenses, often prohibitive. Following the recently fostered concept of constrained modeling, this paper proposes a simple technique for rapid surrogate-assisted yield optimization of narrow- and multi-band antennas. The keystone of the approach is an appropriate definition of the optimization domain. This is realized by considering a few pre-optimized designs that represent the directions of the major changes of the antenna resonant frequencies and operating bands. Due to a small volume of such a domain, an accurate replacement model can be established therein using a small number of training samples, and employed to improve the antenna yield. Verification results obtained for a ring-slot antenna, a dual-band and a triple-band uniplanar dipoles indicate that the optimization process can be accomplished at low cost of a few dozen of EM simulations: 62, 74 and 132 EM simulations, respectively. Result reliability is validated through comparisons with EM-based Monte Carlo simulations.This work was supported in part by the Icelandic Centre for Research (RANNIS) under Grant 206606051, in part by the National Science Centre of Poland under Grant 2017/27/B/ST7/00563, and in part by the Abu-Dhabi Department of Education and Knowledge (ADEK) Award for Research Excellence, in 2019, under Grant AARE19-245."Peer Reviewed

A nested square-shape dielectric resonator for microwave band antenna applications

In this paper, a nested square-shape dielectric resonator (NSDR) has been designed and investigated for antenna applications in the microwave band. A solid square dielectric resonator (SSDR) was modified systematically by introducing air-gap in the azimuth (ϕ-direction). By retaining the square shape of the dielectric resonator (DR), the well-known analysis tools can be applied to evaluate the performance of the NSDR. To validate the performance of the proposed NSDR in antenna applications, theoretical, simulation, and experimental analysis of the subject has been performed. A simple microstrip-line feeding source printed on the top of Rogers RO4003 grounded substrate was utilized without any external matching network. Unlike solid square DR, the proposed NSDR considerably improves the impedance bandwidth. The proposed antenna has been prototyped and experimentally validated. The antenna operates in the range of 12.34GHz to 21.7GHz which corresponds to 56% percentage bandwidth with peak realized gain 6.5dB. The antenna has stable radiation characteristics in the broadside direction. A close agreement between simulation and experimental results confirms the improved performance of NSDR in antenna applications

Terahertz antenna array based on a hybrid perovskite structure

This paper presents a novel terahertz (THz) antenna array design comprising a layered structure of a perovskite material which enhances the radiation characteristics of an antenna overlaid on a conventional metallic antenna element. The simulated antenna consists of a THz gold patch antenna coated with a hybrid perovskite material, methyl-ammonium lead iodide CH3NH3PbI3 which enables the manipulation of the THz electromagnetic waves. In addition to this, we also present a comparison of the antenna properties of the proposed hybrid perovskite material with antennas made of gold and perovskite only. The proposed antenna operates in the frequency band 0.9 -1.2 THz. The simulated impedance bandwidth of the proposed array antenna ranges from 0.9 THz to 1.2 THz with a reflection coefficient (S11) less than -10 dB. The antenna array has a radiation patterns stability on the whole frequency band. The peak gain obtained is 11.4 dBi with perovskite arrays. The hybrid and perovskite antenna array demonstrate high radiation efficiency. The designs presented here will help in realising future wireless communication systems that require miniaturisation, fast reconfigurability and wearability

A Systematic Design of a Compact Wideband Hybrid Directional Coupler Based on Printed RGW Technology

Printed ridge gap waveguide (PRGW) is considered among the state of art guiding technologies due to its low signal distortion and low loss at Millimeter Wave (mmWave) spectrum, which motivates the research community to use this guiding structure as a host technology for various passive microwave and mmWave components. One of the most important passive components used in antenna beam-switching networks is the quadrature hybrid directional coupler providing signal power division with 90° phase shift. A featured design of a broadband and compact PRGW hybrid coupler is propose in this paper. A novel design methodology, based on mode analysis, is introduced to design the objective coupler. The proposed design is suitable for mmWave applications with small electrical dimensions ( 1.2λo×1.2λo ), low loss, and wide bandwidth. The proposed hybrid coupler is fabricated on Roger/RT 6002 substrate material of thickness 0.762 mm. The measured results highlight that the coupler can provide a good return loss with a bandwidth of 26.5% at 30 GHz and isolation beyond 15 dB. The measured phase difference between the coupler output ports is equal 90∘± 5∘ through the interested operating bandwidth. A clear agreement between the simulated and the measured results over the assigned operating bandwidth has been illustrated

An innovative fractal monopole MIMO antenna for modern 5G applications

Proposed in this paper is the design of an innovative and compact antenna array which based on four radiating elements for multi-input multi-output (MIMO) antenna applications used in 5G communication systems. The radiating elements are fractal curves excited using an open-circuited feedline through a coplanar waveguide (CPW). The feedline is electromagnetically coupled to the inside edge of the radiating element. The array's impedance bandwidth is enhanced by inserting a ground structure composed of low-high-low impedance between the radiating elements. The low-impedance section of the ground is a staircase structure that is inclined at an angle to follow the input feedline. This inter-radiating element essentially suppresses near-field radiation between adjacent radiators. A band reject filter based on a composite right/left hand (CRLH) structure is mounted at the back side of the antenna array to reduce mutual coupling between the antenna elements by choking surface wave propagations that can otherwise degrade the radiation performance of the array antenna. The CRLH structure is based on the Hilbert fractal geometry, and it was designed to act like a stop band filter over the desired frequency bands. The proposed antenna array was fabricated and tested. It covers the frequency bands in the range from 2 to 3 GHz, 3.4-3.9 GHz, and 4.4-5.2 GHz. The array has a maximum gain of 6. 2dBi at 3.8 GHz and coupling isolation better than 20 dB. The envelope correlation coefficient of the antenna array is within the acceptable limit. There is good agreement between the simulated and measured results.Dr. Mohammad Alibakhshikenari acknowledges support from the CONEX-Plus programme funded by Universidad Carlos III de Madrid and the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 801538. Funding for APC: Universidad Carlos III de Madrid (Read & Publish Agreement CRUE-CSIC 2022)

High performance antenna-on-chip inspired by SIW and metasurface technologies for THz band operation

In this paper, a high-performance antenna-on-chip (AoC) is implemented on gallium arsenide (GaAs) wafer based on the substrate integrated waveguide (SIW) and metasurface (MTS) technologies for terahertz band applications. The proposed antenna is constructed using five stacked layers comprising metal-GaAs-metal-GaAs-metal. The conductive electromagnetic radiators are implemented on the upper side of the top GaAs layer, which has a metallic ground-plane at its underside. The metallic feedline is implemented at the underside of the bottom GaAs layer. Dual wrench-shaped radiators are framed by metallic vias connected to the ground-plane to create SIW cavity. This technique mitigates the surface waves and the substrate losses, thereby improving the antenna’s radiation characteristics. The antenna is excited by a T-shaped feedline implemented on the underside of the bottom GaAs substrate layer. Electromagnetic (EM) energy from the feedline is coupled to the radiating elements through the circular and linear slots etched in the middle ground-plane layer. To mitigate the surface-wave interactions and the substrate losses in the bottom GaAs layer, the feedline is contained inside a SIW cavity. To enhance the antenna’s performance, the radiators are transformed into a metamaterial-inspired surface (i.e., metasurface), by engraving periodic arrangement of circular slots of sub-wavelength diameter and periodicity. Essentially, the slots act as resonant scatterers, which control the EM response of the surface. The antenna of dimensions of 400 × 400 × 8 μm3 is demonstrated to operate over a wide frequency range from 0.445 to 0.470 THz having a bandwidth of 25 GHz with an average return-loss of − 27 dB. The measured average gain and radiation efficiency are 4.6 dBi and 74%, respectively. These results make the proposed antenna suitable for AoC terahertz applications

On-chip terahertz antenna array based on amalgamation of metasurface-inspired and artificial magnetic conductor technologies for next generation of wireless electronic devices

The paper presents a feasibility study on an innovative terahertz (THz) on-chip antenna array designed to reliably meet the high-performance connectivity requirements for next generation of wireless devices to enable bandwidth intensive applications, superfast fast streaming, bulk data exchange between internet of things (IoT) devices/smartphones and the development of holographic video conferencing. The significantly smaller wavelength of the THz-band and metasurface-inspired and artificial magnetic conductor (AMC) technologies are exploited here to realize an on-chip antenna. Several experimental on-chip antenna arrays of various matrix sizes were investigated for application at millimeter-wave/Terahertz RF front-end transceivers. The technique proposed here is shown to enhance the antennas impedance bandwidth, gain and radiation efficiency. Purely for experimental purposes a 2 × 24 radiation element array was fabricated. It exhibits an average measured gain of 20.36 dBi and radiation efficiency of 37.5% across 0.3–0.314 THz. For proof of the concept purposes a THz receiver incorporating the proposed on-chip antenna was modelled. The results show that with the proposed antenna array a THz receiver can provide a gain of 25 dB when the antenna is directly matched to low-noise amplifier stage

Metamaterial inspired electromagnetic bandgap filter for ultra-wide stopband screening devices of electromagnetic interference

Presented here is a reactively loaded microstrip transmission line that exhibit an ultra-wide bandgap. The reactive loading is periodically distributed along the transmission line, which is electromagnetically coupled. The reactive load consists of a circular shaped patch which is converted to a metamaterial structure by embedded on it two concentric slit-rings. The patch is connected to the ground plane with a via-hole. The resulting structure exhibits electromagnetic bandgap (EBG) properties. The size and gap between the slit-rings dictate the magnitude of the reactive loading. The structure was first theoretically modelled to gain insight of the characterizing parameters. The equivalent circuit was verified using a full-wave 3D electromagnetic (EM) solver. The measured results show the proposed EBG structure has a highly sharp 3-dB skirt and a very wide bandgap, which is substantially larger than any EBG structure reported to date. The bandgap rejection of the single EBG unit-cell is better than − 30 dB, and the five element EBG unit-cell is better than − 90 dB. The innovation can be used in various applications such as biomedical applications that are requiring sharp roll-off rates and high stopband rejection thus enabling efficient use of the EM spectrum. This can reduce guard band and thereby increase the channel capacity of wireless systems

High performance antenna‑on‑chip inspired by SIW and metasurface technologies for THz band operation

In this paper, a high-performance antenna-on-chip (AoC) is implemented on gallium arsenide (GaAs) wafer based on the substrate integrated waveguide (SIW) and metasurface (MTS) technologies for terahertz band applications. The proposed antenna is constructed using five stacked layers comprising metal-GaAs-metal-GaAs-metal. The conductive electromagnetic radiators are implemented on the upper side of the top GaAs layer, which has a metallic ground-plane at its underside. The metallic feedline is implemented at the underside of the bottom GaAs layer. Dual wrench-shaped radiators are framed by metallic vias connected to the ground-plane to create SIW cavity. This technique mitigates the surface waves and the substrate losses, thereby improving the antenna’s radiation characteristics. The antenna is excited by a T-shaped feedline implemented on the underside of the bottom GaAs substrate layer. Electromagnetic (EM) energy from the feedline is coupled to the radiating elements through the circular and linear slots etched in the middle ground-plane layer. To mitigate the surface wave interactions and the substrate losses in the bottom GaAs layer, the feedline is contained inside a SIW cavity. To enhance the antenna’s performance, the radiators are transformed into a metamaterial inspired surface (i.e., metasurface), by engraving periodic arrangement of circular slots of subwavelength diameter and periodicity. Essentially, the slots act as resonant scatterers, which control the EM response of the surface. The antenna of dimensions of 400 × 400 × 8 μm3 is demonstrated to operate over a wide frequency range from 0.445 to 0.470 THz having a bandwidth of 25 GHz with an average return-loss of − 27 dB. The measured average gain and radiation efficiency are 4.6 dBi and 74%, respectively. These results make the proposed antenna suitable for AoC terahertz applications