Wide Bandwidth Research Articles

An optimized surrogate model and algorithm with rapid multi-parameter processing capability for antenna design

A methodology based on an optimized surrogate model and Non-dominated Sorting Genetic Algorithm III(NSGA-III) algorithm is proposed to address the long design cycle issues that conventional antennas encounter, with fast multiple parameters processing capability. A Temporal Convolutional Network (TCN) network model with high fitting efficiency and a simple structure is first developed as a surrogate model for antenna performance prediction, taking antenna dimensional parameters as input and outputting the reflection coefficient (S11) and gain of the antenna. Then, an adaptive NSGA-III algorithm with enhanced search efficiency is presented. By combing it with the prior TCN surrogate model, the parameter optimization for a 5G millimeter-wave antenna design is realized. Results show that the proposed method achieves a remarkable reduction in Mean Squared Error (MSE) by 12.489 % and 3.277 % respectively, while also presents a decreased running time by 2.670 % and 70.419 % respectively, as compared to the Convolutional Neural Networks (CNN) and Bidirectional Long Short-Term Memory (BiLSTM) network models. The proposed method can rapidly and accurately perform the optimization task of multiple antenna parameters, demonstrating its feasibility and effectiveness for antenna applications requiring wide bandwidth, low loss and high gain.

The high-Q THz stereo metasurface sensor based on double toroidal dipole with wide operating angle bandwidth

A highly sensitive terahertz stereo metasurface sensor, characterized by a high quality factor (Q-factor) and based on dual toroidal dipole (TD) resonance, has been proposed. The optimal structural parameters are ascertained by comparing the pertinent parameters of the stereo and planar structures in relation to TD modal excitation. The effective excitation of the TD mode is demonstrated using the calculations of multipole scattered power, reflection spectra, surface currents, electric fields, and magnetic field distributions. It is crucial that the stereo metasurface exhibits simplicity and that the dual TD resonance can be readily excited through simple adjustments in the distance and height of the intermediate gap. It also demonstrates exceptionally high sensitivity and Q-factor, both of which are essential for sensing applications. Moreover, the proposed stereo terahertz metasurface sensor still shows excellent sensing performance in a wide range of incidence angles (±40°), which is of great significance for practical applications. In conclusion, this structure offers a novel design framework for high-performance terahertz sensors based on the TD mode.

Optimizing MOF‐Derived Electromagnetic Wave Absorbers through Gradient Pore Regulation for Pareto Improvement

AbstractPorous materials emerging as potential high‐efficiency electromagnetic (EM) wave absorbers confront a critical trade‐off between impedance matching and attenuation capability. In this study, a versatile strategy is reported to overcome this challenge by constructing gradient pores via solvent‐assisted linker exchange for the fabrication of metal‐organic framework (MOF) derived Fe/Fe3Co7/Co/C composites with high porosity. The impedance and attenuation characteristics of single‐pored and gradient‐pored derivatives are investigated through combined experimental and simulation approaches. Simulated space EM field, loss density, and Smith charts reveal significantly enhanced EM interactions and optimized impedance within the pores. Compared to individual MOF derivatives, the gradient derivative exhibits improved impedance matching from the large‐pored shell and superior attenuation capability from the small‐pored core, giving rise to a Pareto improvement in EM absorption with strong reflection loss (−64.7 dB) and wide effective adsorption bandwidth (5.8 GHz) at a thickness of 2.5 mm. This work not only advances a novel gradient pore strategy for constructing efficient absorbers with enhanced impedance matching and attenuation capability, but also sheds light on the underlying mechanisms of EM interaction with varied porosity, offering insights for extended designs in magnetic, electric and optic devices.

Dielectric resonator antenna with square slot dgs and amc support for gain enhancement

A miniatured Dielectric Resonator Antenna (DRA) designed on Defected ground structure (DGS) with backing of Artificial Magnetic Conductor (AMC) is presented in this work. The designed antenna showing wide bandwidth to cover WLAN, Wi-Fi and 5G communication applications under sub 6 GHz range and X-band for satellite communication device applications. Antenna occupying the dimension of 35 × 30 × 1.6 mm on Rogers RT-duroid 5880 substrate material, DRA on alumina material of permittivity 9.8 with dimension of 25 × 20 × 10 mm and the AMC surface of dimension 60 × 58 × 1.6 mm on FR4 substrate material. The constructed antenna resonating in the wide band from 3.4–11.5 GHz by holding overall bandwidth of 8.11GHz and an impedance bandwidth of 139%. The DRA placed over the antenna providing the axial ratio at two bands of 4.2–6 GHz and 9.2 to 11.4 GHz with axial bandwidth of 36% and 28% respectively. The placement of AMC structure beneath the antenna exhibiting an improvement in gain of 9% and an average gain attained in the operating band is around 7.2 dBi. The unique combination of monopole antenna with DRA and AMC providing excellent bandwidth, axial ratio and gain.

Study on low-mid-frequency broadband sound absorption properties of bending acoustic metamaterials with embedded porous materials

With the rapid development of the traffic industry, noise issues are becoming increasingly serious, and the traditional noise control technologies have the problems of poor low-frequency noise absorption and narrow bandwidth. This study proposes a variable-section bending acoustic metamaterial with an embedded porous material (VS_BAMP). A theoretical model of the VS_BAMP unit is developed based on the Johnson-Champoux-Allard (JCA) model and the impedance transfer method. The sound absorption unit with a thickness of 48 mm exhibits a quasi-perfect (α = 0.98) at 736 Hz, and an efficient sound absorption (α > 0.8) in the range of 574 Hz–966 Hz. Based on the complex frequency plane method, this work designs sound absorption units that exhibit perfect sound absorption at discrete frequencies. By connecting two different absorption units (PVS_BAMP) in parallel, efficient sound absorption from 424 Hz to 1500 Hz is achieved. Finally, the accuracy of the theoretical model is verified by experiments and simulations, confirming the effective sound absorption of PVS_BAMP structure in the middle and low frequency bands. The prepared PVS_BAMP is highly adjustable, has a wide bandwidth, and can be prepared through a simple manufacturing process. Our results can provide a theoretical basis for the design of compact low-mid-frequency broadband noise reduction structures for practical application.

Enhancing phase modulation and group delay in reflective Huygens metasurfaces via a Fabry-Perot cavity

Huygens metasurfaces exhibit excellent optical properties such as 2π phase modulation and slow light effects. However, they face challenges including wide bandwidth and low group delay due to their high radiation losses. Here, we propose a reflective Huygens metasurface coupled with an F-P cavity. We demonstrate that F-P resonance modes can couple with magnetic-quasi-bound-state (M-QBIC) and electric-quasi-bound-state (E-QBIC) in the Huygens metasurface through constructive interference, significantly enhancing the quality factors of both QBICs. Through structural parameter optimization, our reflective Huygens metasurface achieves 4π phase modulation and a high group delay of up to 166 ps. Compared to the non-coupled Huygens metasurface with the same structural asymmetry, the group delay of the F-P coupled reflective Huygens metasurface is enhanced by up to 30 times. Our design reduces the fabrication precision requirements for Huygens metasurfaces, enabling similar group delays to be achieved in low-symmetry coupling structures as in highly symmetric non-coupling structures. Additionally, the performance of this metasurface shows robustness to changes in incident light polarization. This design highlights the potential for achieving high-quality factors, large phase modulation, and large group delay, offering new avenues for the design of highly sensitive tunable devices, efficient nonlinear optical devices, and narrowband slow light devices.

Simple and hybrid metalens with high polarization conversion efficiency for near-infrared spectrum

Thanks to their ability to control light, research on metalenses is developing rapidly. However, it is still quite difficult to design broadband metalenses with high polarization conversion efficiency. In this study, an alternative plasmonic material, aluminum-doped zinc oxide, is presented for metalens operating in near-infrared regime. We propose simple and hybrid metalenses with high polarization conversion efficiency and high transmission values that can focus efficiently in a wide near-infrared bandwidth (700–1000 nm). We design metalens consisting of subwavelength aluminum-doped zinc oxide nanoblocks based the Pancharatnam-Berry phase method and utilizing the finite-difference time-domain method. The polarization conversion efficiency (minimum 87 %) and transmission values (minimum 85 %) calculated for the metalens unit cell are higher than those previously obtained over the entire 300 nm bandwidth. In addition, we propose hybrid metalens to focus the incident beam in right and left handed circular polarized states in the studied frequency range. The presented aluminum-doped zinc oxide metalens with high polarization conversion efficiency and transmission values can find a place in the applications of near-infrared nanophotonic systems.

Two-layered optimized metamaterial antenna with high gain and wide bandwidth for 5G mm-Wave applications

A two-layered high gain and wide bandwidth metamaterial antenna working at 29 GHz for mm-Wave applications is proposed in this paper. The metamaterial antenna has an overall compact size of 12.5 x 12.5 x 7.28 mm3. It is realized with a Rogers Duroid 5880 dielectric layer 0.78 mm thick used as substrate and a Rogers RO3010 dielectric layer 1.5 mm thick at distance 5 mm above the radiation element. The radiation element is composed of a square-cut-at-the-four-corners, patch antenna with probe pin feeding. In addition, for further antenna performance enhancement, negative refractive index printed metamaterials surround the patch antenna offering bandwidth and gain enhancement. Simulated results show a significantly wide bandwidth of 7.91 GHz ranging from 26.04 GHz to 33.95 GHz and a high peak realized gain of 12.2 dB. These features make the antenna a good candidate for 5G mm-Wave applications.

Predicting plants in the wild: Mapping arctic and boreal plants with UAS-based visible and near infrared reflectance spectra

Biophysical changes in the Arctic and boreal zones drive shifts in vegetation, such as increasing shrub cover from warming soil or loss of living mat species due to fire. Understanding current and future responses to these factors requires mapping vegetation at a fine taxonomic resolution and landscape scale. Plants vary in size and spectral signatures, which hampers mapping of meaningful functional groups at coarse spatial resolution. Fine spatial grain of remotely sensed data (<10 cm pixels) is often necessary to resolve patches of many Arctic and boreal plant groups, such as bryophytes and lichens, which are significant components of terrestrial vegetation cover. Separation of co-occurring small vegetation patches in images also requires high spectral resolution. Our goal here was to test the capabilities of UAS-based imaging spectroscopy for mapping plant functional types (PFT) using high spatial and spectral resolution data over Arctic and boreal vegetation at four sites in central Alaska. We then tested several Machine and Deep learning models of PFT cover using the reflectance spectra. The best models were very simple, balancing both bias (overfitting caused by imbalance sample sizes) and variance (fit to the independent validation data), explaining > 50 % of the independent ground cover estimation and > 84 % accuracy in estimating validation pixels. We explored the impact of spectral resolution on PFT mapping by including vegetation indices and a gradient of narrow (5 nm) to wide (50 nm) band features in our classification models across. Vegetation indices were the most important predictors for classifying PFTs, while including band features improved models, with narrow and wide bandwidths having similar importance but models with wide bandwidths performing slightly better. We conclude that Arctic and boreal PFT reflectance can be pooled across sites for mapping with relatively few labeled pixels. Underfit, simple algorithms outperformed deep learning, at least with these small sample sizes, in classifying PFTs by balancing bias and variance. Future work should aim to increase the number of labeled pixels and the detail of labels to further improve mapping taxonomic precision.

A wideband flexible antenna utilizing PMMA/PVDF‐HFP/PZT polymer composite film and silver‐based conductive ink for wearable applications

AbstractThe relentless drive towards miniaturization and seamless integration of electronic components in wireless communications and wearable devices has significantly increased the demand for flexible, cost‐effective composites with high dielectric constants and low losses. This study presents a wideband, low‐profile, and flexible antenna with excellent on body radiation performance for wearable applications. The antenna is designed using a low‐loss composite film based on PMMA‐PVDF‐HFP‐PZT and silver‐based ink. The proposed flexible antenna exhibits a wide bandwidth of 132.16% with a voltage standing wave ratio (VSWR) of less than two. It achieves a peak gain of 2.76 dBi at 2.92 GHz and maintains a maximum radiation efficiency of 80% across the 1.26–6.17 GHz frequency range. These characteristics demonstrate that the antenna is an effective solution for achieving high data rates and reliable communication links. The antenna's suitability for wearable applications is assessed by testing it on a simulated human body and analyzing its behavior under physical deformation. The results under bending showed only a minimal frequency detuning, which is negligible given the antenna's wide operational bandwidth. The specific absorption rate (SAR) analysis shows values of approximately 1.88 W/kg at 3.5 GHz with an input power of 0.5 W, and 0.279 W/kg at 5.8 GHz with an input power of 0.45 W, which complies with established safety limits for exposure. Overall, these results suggest that the proposed antenna is a viable solution for integration into wearable medical devices, such as a doctor's chest badge, enabling noncontact interactions and reducing the risk of bacterial contamination.

A low-profile ultra-wideband magneto-electric dipole antenna for ground penetrating radar

ABSTRACT Ultra-wideband antennas that operate at low frequencies usually have a large geometry, which makes them very limited in practical engineering application environment where space is often constrained. In this paper, a novel low-frequency low-profile ultra-wideband magneto-electric (ME) dipole antenna is designed for the application in ground penetrating radar (GPR) to detect deeply buried targets. The antenna is designed at the operation frequency of 230 MHz, so that the objects that are buried as deep as 1.5 m can be detected. Compared to the traditional low-frequency _antennas, it has a profile as low as 740 mm × 140 mm × 150 mm ( 0.49 λ × 0.09 λ × 0.10 λ ). Based on the simulation analysis and validation measurements, the proposed ME dipole antenna has a wide impedance bandwidth for S 11 < − 10 dB from 135 MHz to 382 MHz even when environmental influence is considered. The antenna is further validated with a GPR experiment, where a pipeline with a diameter of about 200 mm at 1200 mm beneath the road surface is successfully detected by an impulse GPR system where the proposed antennas are integrated.

MOF-derived ZnCo2O4 @ Ti3C2TX nanosheet with high microwave absorption

Abstract Electromagnetic wave absorbing (EWA) materials have a wide application in military technology, so it is necessary to develop EWA materials with lightweight, and wide absorption bandwidth and strong absorption. Novel two-dimensional material (MXene) with high dielectric constant property and unique structure has attracted extensive focus in microwave absorption. However, the high conductivity of MXene limits its application in microwave absorption. In this work, ZnCO2O4 nanoparticles were obtained via a hydrothermal method and subsequent heat treatment. Then it was anchored on MXene nanosheets. The effective absorption bandwidth (EAB) of the ZnCO2O4@Ti3C2Tx is 4.77GHz at 1.5mm thickness. Composites show great potential in the field of designing a new generation of efficient and lightweight microwave absorbers, which are expected to be used in various EWA applications.

A millimeter‐wave ultra‐wideband triplexer with high isolation and high power

AbstractThis paper provides a compact, noncontiguous, high isolation, manifold triplexer operating from 25.8 to 49.5 GHz, a 62.95% wide fractional operating bandwidth. The triplexer is composed of three waveguide bandpass filters with Chebyshev responses. The initialization and loop optimization strategy of the triplexer are given. To eliminate undesired high‐order mode transmission between common port and filters, ridged‐waveguide topology, tuning screws, capacitive windows, and narrowing the wide edges of resonant cavities for the third filter are employed. The measured results and simulated ones are in good agreement. To our knowledge, this is the most broadband, high‐power triplexer demonstrated to date.

Millimeter micro‐coaxial beam steering array for high‐speed satellite communications

AbstractWide‐band low‐loss passive beam steering array presents to be essential part of the RF front‐ends for high‐speed detection during deep space exploration missions. In this letter, the copper‐based additive manufacturing technology is proposed for the implementation of low‐profile (~0.1λ) antenna design. Adopting the micro‐coaxial line as the basic design unit enables wide bandwidth design. In addition, the broadband designs of Butler matrix, planar antenna element, and transmission transitions are proposed, respectively. The miniaturization of the metallic patch antenna is realized using a double slotted design, ensuring an array space of ~0.5λ, which beneficial for the low‐lobe beam steering. Experimental results show that the antenna array with an overall size of 39 × 29 × 0.5 mm presents four beams located at ±14° and ±43°, respectively. The bandwidth of return loss better than −10 dB ranges from 65 to 71 GHz. The measured result matches well with the simulated ones, which makes its potential operation for satellite applications.

High isolation MIMO antenna array for multiband terahertz applications

The advancement of future technology seeks to create wireless systems capable of achieving faster data transfer rates. One solution to confront this challenge is by employing Multiple-Input Multiple-Output (MIMO) systems. Nonetheless, the primary obstacle in assessing MIMO performance revolves around the size and spacing of the antennas to maintain isolation among the ports. Consequently, it is essential to devise an approach to tackle these challenges, with the utilization of a DGS as a viable and promising approach. Hence, in this study, we developed a dual-frequency MIMO system featuring two linear array antennas with two elements each and configured to function at 128 GHz and 178 GHz. Initially, this design is conceived as a single-element structure before evolving into a two-element MIMO antenna array configuration. The antenna's physical dimensions are 2.7 × 3.65 × 0.15 mm3, and it consists of two linear array nodes positioned at a separation distance of 0.18 mm. Additionally, the antenna delivers peak gains of 5.16 dB and 6.24 dB at frequencies of 128 GHz and 178 GHz, respectively. The values of various MIMO performance indicators meet stringent standards with ECC values below 0.012 and a DG of approximately 10 dB. Furthermore, the TARC remains below 0 dB. The aim of this research is to create a novel design for a THz antenna that can achieve a wide bandwidth and a high gain while maintaining the standard compact antenna size necessary for THz applications.

Unveiling Frequency-dependent Eclipsing in Spider Millisecond Pulsars Using Broadband Polarization Observations with the Parkes

This study presents an orbital-phase-dependent analysis of three black widow spider millisecond pulsars (BW MSPs), aiming to investigate the magnetic field within the eclipse environment. The ultrawide-bandwidth low-frequency receiver of the Parkes Murriyang radio telescope is utilized for full polarization observations covering frequencies from 704−4032 MHz. Depolarization of pulsed emission is observed during the eclipse phase of three BW MSPs, namely PSR J0024−7204J, PSR J1431−4715, and PSR J1959+2048, consistent with previous studies of other BW MSPs. We estimated orbital-phase-dependent rotation measure values for these MSPs. The wide bandwidth observations also provided constraints on the eclipse cutoff frequency for these BW MSPs. For PSR J0024−7204J, we report temporal variation of the eclipse cutoff frequency coupled with changes in the electron column density within the eclipse medium across six observed eclipses. Moreover, the eclipse cutoff frequency for PSR J1431−4715 is determined to be 1251 ± 80 MHz, leading to the conclusion that synchrotron absorption is the primary mechanism responsible for the eclipsing. Additionally, for PSR J1959+2048, the estimated cutoff frequency exceeded 1400 MHz, consistent with previous studies. With this investigation, we have doubled the sample size of BW MSPs with orbital-phase-resolved studies, allowing a better probe of the eclipse environment.

Optically Delaying a Radio Frequency–Linear Frequency-Modulated (RF-LFM) Pulse Using Kerr Comb Carriers and Off-the-Shelf Concatenation of a Linearly Chirped Fiber Bragg Grating and a Chirped-and-Sampled Fiber Bragg Grating

We demonstrate a low latency delay of a radio frequency (RF)–linear frequency-modulated (LFM) pulse by modulating it onto optical carriers from a Kerr comb and sending the signal through a concatenation of off-the-shelf linearly chirped fiber Bragg gratings (LC-FBGs) and chirped-and-sampled FBG (CS-FBG). We characterize the frequency response and latency of the LC-FBG and CS-FBG. Then, experimentally, the LFM pulse performance is characterized by measuring the peak sidelobe level (PSL) at the output of the tunable delay system. The experiment, performed with an LFM pulse of 1 GHz bandwidth at a 10 GHz center frequency, shows a PSL better than 34.4 dB, attesting to the high quality of the buffer RF transfer function. Thus, the proposed optical memory buffer architecture, utilizing compact devices based on a Kerr comb and FBGs, offers several benefits for delaying LFM pulses, including (i) a larger tunable delay range, (ii) low latency, (iii) wide bandwidth, and (iv) high PSL.

Multifunctional electromagnetic wave absorbing carbon fiber/Ti3C2TX MXene fabric with ultra-wide absorption band

In order to provide electronics and aerospace equipment with effective immunity to electromagnetic interference and to improve their adaptability to very harsh electromagnetic environments, high-performance electromagnetic wave-absorbing materials are urgently needed for civil and military applications. Unfortunately, their effective absorption bandwidth width is still unsatisfactory (<10 GHz) due to the insufficient regulation of their component mixing and microstructure. By employing nanocage-structured UiO-66 as a doping phase, MXene/ZrO2/tungsten-doped carbon (MXene/ZrO2/W-C) interpenetrating fiber networks were prepared by the electrostatic spinning method. According to the experimental results, the introduction of the dopant phase and the formation of the interpenetrating network significantly improves impedance matching, resulting in a wide absorption bandwidth of 11.12 GHz for the composites, completing the coverage of the X and Ku bands. The radar scattering cross section of MXene/ZrO2/W-C has been simulated using three-dimensional electromagnetic field simulation, and as a result of its excellent stealth performance, it is able to generate corresponding electromagnetic responses in radar detection environments that exhibit different far-field emission bands. Further, MXene/ZrO2/W-C exhibits outstanding hydrophobicity, corrosion resistance, and temperature resistance. These characteristics allow it to be used for the preparation of electromagnetic wave (EMW) absorbing devices for complex environmental applications. It is important to note that the results of this study will be extremely useful in the development of composites based on MXene with ultra-wide absorption bands as well as in the analysis of EMW absorption mechanisms.

Enhancement of Microwave Absorption Properties of Crystal‐Engineered Perovskite Oxide Using Cobalt Ferrite

A multiferroic composite that comprises of a non‐ferromagnetic ferroelectric material with a high dielectric constant and a non‐ferroelectric ferromagnetic material with a high magnetostriction is of tremendous interest as microwave absorption material due to its applicability in tunable microwave phase shifters, resonators, filters, absorbers, etc. In the previous work, the solid solution of strontium titanate and sodium bismuth titanate (Sr0.5(Na0.5Bi0.5)0.5TiO3, SNBT50), which is observed to possess a very high dielectric constant at room temperature (Ferroelectrics, Vol 583, 252–263 [2021]), is successfully reported. Thus, in this work, a core–shell magnetoelectric composite is prepared by coating highly ferromagnetic and magnetostrictive cobalt ferrite onto a diamagnetic but strongly ferroelectric SNBT50 to enhance its magnetic properties and to investigate the modification in microwave absorption. Detailed characterization of electric and magnetic parameters in microwave frequency range (1–20 GHz) reports substantial enhancement in the magnetic permeabilities as well as the magnetic loss of the composite system, as opposed to bare SNBT50. This results in improved impedance matching in the system and enhanced microwave absorption, with a minimum reflection loss (RL) of −20.19 dB and an increased effective absorption bandwidth of 4.56 GHz at a mere 2.7 mm absorber length. Consequently, in this investigation, a promising pathway is established for the development of multiferroic composites with favorable magnetoelectric coupling at room temperature that possesses wide absorption bandwidth and suitable RL, making them highly suitable for use in multiferroic‐based microwave components.

Compact narrow slot antenna with stable radiation pattern and wide bandwidth

One of the most crucial parameters for any antenna is bandwidth. Over the whole extended bandwidth, the antenna achieves a high gain of 5dBi and a steady bidirectional radiation pattern. A novel design concept for increasing bandwidth and maintaining a consistent radiation pattern has been proposed for the radiated fields of a slot antenna. First, the radiated fields of the standard slot antenna are examined theoretically using characteristic modes (CMs). Its three CMs vibrate at 2.45, 4.78, and 7.17 GHz, respectively, according to the results. CM1 and CM3 both continue to emit radiation in both directions, but CM2 generates a radiation null in the broadside direction. After that, the linear slot is appropriately folded to change CM2’s non-bidirectional pattern into a bidirectional one, allowing for the broad bandwidth use of the neighbouring CM1 and CM2. The narrow slot is then used to create the stepped scheme, which reallocates these dual modes in close proximity to one another. By using these designs, the antenna’s radiation pattern consistency and small size of 0.022λo can be preserved, but its impedance bandwidth can be significantly expanded. After that, the proposed antenna is constructed and assessed. Measurements show that the antenna has a broad bandwidth (|S11|<−10 dB) of around 35.14%, covering the frequency range of 3.3 to 4.6 GHz.