Dual Band Research Articles

Realizing Stable Luminescence in Antimony Doped Hybrid Tin(IV) Chloride toward Full Spectrum WLED and Anticounterfeiting Applications.

The outstanding optical properties empower Sb3+-doped zero-dimensional hybrid metal halides as cutting-edge luminescent materials. In this research, we present an efficient hybrid tin chloride, TEA2SnCl6:Sb3+ (TEA = tetraethylammonium), with broad dual emission bands peaking in the blue and orange regions that arise from the singlet and triplet state emissions of [SbCl5]2-, respectively. TEA2SnCl6:Sb3+ demonstrates a high photoluminescence quantum yield (PLQY) of 83.5% under 328 nm excitation, while 358 nm light induces an orange emission with a PLQY of 92.5% and a low thermal quenching behavior (73.9% at 423 K). Benefiting from the appealing luminescence properties of TEA2SnCl6:Sb3+, a full spectrum white light-emitting diode (WLED) device and an anticounterfeiting model were constructed, affirming the potential use of Sb3+-doped TEA2SnCl6 hybrid metal halide in versatile application fields.

A dual-band meandered line antenna loaded with metasurface for wireless applications

In this paper, a metamaterial inspired meandered line loaded antenna with dual-band characteristics for wireless applications is presented. Initially, the antenna is loaded with a single meandered line structure and operates over a single band with a center frequency of 5.64 GHz and circularly polarized (CP) radiation. Further, it is loaded with two more similar meandered line structures inducing an extra band with a center frequency of 3.4 GHz and hence operating as a dual band antenna with an impedance bandwidth of 11.4% and 33.7%, respectively, exhibiting CP radiation in its second band. Moreover, the antenna is backed with a metasurface (MS) at the ground side with a separation of 18.4 mm to enhance the gain and radiation of the antenna. The antenna exhibits good radiation characteristics with peak gains of 7.66 dBi and 8.7 dBi in the first and second bands, respectively. The antenna is fabricated, and promising experimental results have been observed.

Integration of dual band radio waves and ensemble-based approach for rice moisture content determination and localisation

Maintaining optimal moisture content in grain storage is critical to ensuring adequate supply throughout the year, but it presents a significant challenge. Current moisture measurement methods often necessitate sophisticated and costly equipment. This paper introduces an approach employing real-time rice moisture content determination and detection of spoilage (specifically wet spots) within a storage facility achieved through the utilisation of radio waves operating at 2.4 GHz and 868 MHz, along with an ensemble-based machine learning algorithm. Experimental samples spanning from 12% to 30% moisture levels were collected, then subjected to pre-processing, and subsequently employed to train the Ensemble-based Rice Moisture Content and Localisation (eRMCL) algorithm. The eRMCL produced an effective prediction of both rice moisture content and the localisation of wet spots within the grain storage unit. The results show that compared to support vector machine, random forest, and machine learning methods, the eRMCL algorithm had the best performance metrics, with an accuracy of 94.8% in predicting the moisture content and location of spoilage in storage. The measurement of moisture content and the identification of wet spots in rice storage using the dual frequency wave approach were found to be more accurate than with a single frequency band. Thus, the dual frequency band is a novel method for the determination of the moisture content of stored rice and the localisation of the spoilage area.

Fabrication of compact substrate integrated waveguide dual band bandpass filter using complementary split-ring resonators for C and X band applications

This article presents a compact dual-band Bandpass Filter(BPF) based substrate integrated waveguide(SIW) used for C and X band applications. Complementary split-ring resonators(CSRR) are loaded into the waveguide surface to obtain more advantages of compactness and good performance. The SIW cavity undergoes initial optimization utilizing the powerful genetic algorithm, renowned for its robustness in solving complex problems, before proceeding to simulation with Ansys HFSS software with loaded CSRRs. The filter displays two passbands: the first has a bandwidth of 2 GHz and resonates at 6.8 GHz, while the second has a bandwidth of 5,55 GHz and resonates at 10.3 GHz. Moreover, with two resonance frequencies, the developed BPF has the benefit of low insertion loss(S21=-1.7dB and -1.9 dB) and improved return loss: (S11=-24dB and -22 dB) respectively. Furthermore, the proposed combination not only allows the implementation of a forward-wave passband propagating below the characteristic cutoff frequency of the waveguide but also exhibits good rejection, demonstrated by the presence of two transmission zeros with rejection of -16 dB and -19 dB, attained at 7.4 GHz and 14.8 GHz respectively. The proposed SIW BPF was designed using a 0.6mm thick FR4 dielectric substrate measuring 13mm × 15mm. The filter is manufactured to validate the concept and the measured results agree well with the simulation. With all these advantages: compact size, high rejection, and good filtering response, the proposed SIW BPF became suitable for microwave applications.

Spinel-Type Structured Phosphor Near-Infrared-II Emission: Intervalence Charge Transfer and Hetero-Valent Chromium Pairs.

Near-infrared (NIR) emitting phosphors draw much attention because they show great applicability and development prospects in many fields. Herein, a series of inverse spinel-type structured LiGa5O8 phosphors with a high concentration of Cr3+ activators is reported with a dual emission band covering NIR-I and II regions. Except for strong ionic exchange interactions such as Cr3+-Cr3+ and Cr3+ clusters, an intervalence charge transfer (IVCT) process between aggregated Cr ion pairs is proposed as the mechanism for the ~1210 nm NIR-II emission. Comprehensive structural and luminescence characterization points to IVCT between two Cr3+ being induced by structural distortion and further enhanced by irradiation. Construction of the configurational energy level diagram enabled elucidation of this transition within the IVCT process. Therefore, this work provides insight into the emission mechanism within the high Cr3+ concentration system, revealing a new design strategy for NIR-II emitting phosphors to promote its response.

Photo-isomerization enabled reversible wavelength switching in fiber random laser for color image encryption

Random lasers owing the functionality of generating random spectra facilitate the chaotic encrypted systems essential for cryptography in the current information epoch. Nevertheless, single wavelength bands of random lasers provide an unsuitable key for image encryption that causes outline interpretation and a fragile complex dual chaotic encryption demanding secured image encryption. This research presents an inevitable development of a reversible switchable wavelength fiber random laser composed of the mixture of highly polarized intramolecular charge transfer dye molecules and the optimum concentration of titanium dioxide acting as gain and efficient scattering mediums respectively within a polyvinyl alcohol matrix. This mixture with a certain ratio is coated on a fiber employing a dip coated method, followed by a layer of polydimethylsiloxane to facilitate with high coefficient of thermal expansion. Random laser emission is enabled with dynamically switchable wavelengths obeying the excited state intramolecular proton transfer phenomenon under the photo-isomerization. The optimum scatters concentration yields a lower threshold of 32 µJ/cm2 with full width at half maximum of 0.4 nm and dual emission reversible switchable wavelength bands centered around 443 nm and 464 nm attributed to inter charge transfer feature of the dye molecules. Thereby, the dual reversible switchable wavelength bands feed as input for a dual chaotic color image encryption system. Further, in this integrated system, beam divergence of random laser emissions remains less than 20° during both situations of with- and without irradiation. This delicate approach paves the way in laying the foundation about the applicability of fiber random lasers in an information security system.

A MIMO antenna array featuring dual wideband and high gain for 5G NR n257/n258/n260/n261 bands applications

This article introduces the development of a Multi-Input Multi-Output (MIMO) antenna array specifically designed for 5G millimeter-wave (mm-wave) communication systems. The suggested MIMO configuration consists of four antenna arrays, each comprising two elements arranged evenly, operating at 26 GHz and 37 GHz with a physical size of 43 mm × 32.5 mm × 0.8 mm using a Rogers RT/Duroid 5880 substrate. The proposed MIMO configuration provides dual bands, with frequency bands extending from 23.8 to 30 GHz (IBW = 6.2 GHz) and 32.5 to 41 GHz (IBW = 8.5 GHz), accompanied by high gains of around 18.5 dB for the first band and 16.4 dB for the second band. The designed antenna also shows broad circular polarization with 3 dB Axial Ratio Bandwidth (ARBW) of 4.75 GHz, ranging from 25.05 to 29.8 GHz. A physical prototype has been fabricated for the proposed 4 port MIMO antenna array and tested to verify the results acquired from simulations. The comparison between simulation and measurement results in terms impedance and radiation parameters such as S-parameters, isolation, gain, axial ratio (AR), efficiency, radiation patterns, and various necessary MIMO metrics demonstrates a strong alignment. This antenna covers various 5G New Radio (NR) application bands such as 28 GHz n257 (26.50–29.50 GHz), 26 GHz n258 (24.25–27.50 GHz), 28 GHz n260 (37–40 GHz) and 28 GHz n261 (27.50–28.35 GHz) utilized across different countries including Canada, Australia, China, France, Germany, India, Italy, Japan, South Korea, United Kingdom, and United States of America.

A tunable, dual band graphene terahertz absorber with equivalent circuit modeling

A tunable, dual band graphene terahertz absorber with equivalent circuit modeling

Integrating deep convolutional surrogate solvers and particle swarm optimization for efficient inverse design of plasmonic patch nanoantennas

Abstract Plasmonic nanoantennas with suitable far-field characteristics are of huge interest for utilization in optical wireless links, inter-/intrachip communications, LiDARs, and photonic integrated circuits due to their exceptional modal confinement. Despite its success in shaping robust antenna design theories in radio frequency and millimeter-wave regimes, conventional transmission line theory finds its validity diminished in the optical frequencies, leading to a noticeable void in a generalized theory for antenna design in the optical domain. By utilizing neural networks, and through a one-time training of the network, one can transform the plasmonic nanoantennas design into an automated, data-driven task. In this work, we have developed a multi-head deep convolutional neural network serving as an efficient inverse-design framework for plasmonic patch nanoantennas. Our framework is designed with the main goal of determining the optimal geometries of nanoantennas to achieve the desired (inquired by the designer) S 11 and radiation pattern simultaneously. The proposed approach preserves the one-to-many mappings, enabling us to generate diverse designs. In addition, apart from the primary fabrication limitations that were considered while generating the dataset, further design and fabrication constraints can also be applied after the training process. In addition to possessing an exceptionally rapid surrogate solver capable of predicting S 11 and radiation patterns throughout the entire design frequency spectrum, we are introducing what we believe to be the pioneering inverse design network. This network enables the creation of efficient plasmonic antennas while concurrently accommodating customizable queries for both S 11 and radiation patterns, achieving remarkable accuracy within a single network framework. Our framework is capable of designing a wide range of devices, including single band, dual band, and broadband antennas, with directivities and radiation efficiencies reaching 11.07 dBi and 75 %, respectively, for a single patch. The proposed approach has been developed as a transformative shift in the inverse design of photonics components, with its impact extending beyond antenna design, opening a new paradigm toward real-time design of application-specific nanophotonic devices.

Dual band half-hexagonal shape with additional slot wearable microstrip antenna

Dual band half-hexagonal shape with additional slot wearable microstrip antenna

Excitation/emission-enhanced heterostructure photonic crystal array synergizing with "DD-A" FRET entropy-driven circuit for high-resolution and ultrasensitive analysis of ctDNA

Circulating tumor DNA (ctDNA) is an emerging biomarker of liquid biopsy for cancer. But it remains a challenge to achieve simple, sensitive and specific detection of ctDNA because of low abundance and single-base mutation. In this work, an excitation/emission-enhanced heterostructure photonic crystal (PC) array synergizing with entropy-driven circuit (EDC) was developed for high-resolution and ultrasensitive analysis of ctDNA. The donor donor−acceptor FÖrster resonance energy transfer ("DD-A" FRET) was integrated in EDC based on the introduction of simple auxiliary strand, which exhibited higher sensitivity than that of traditional EDC. The heterostructure PC array was constructed with the bilayer periodic nanostructures of nanospheres. Because the heterostructure PC has the adjustable dual photonic band gaps (PBGs) by changing nanosphere sizes, and the "DD-A" FRET can offer the excitation and emission peak with enough distance, it helps the successful matches between the dual PBGs of heterostructure PC and the excitation/emission peaks of "DD-A" FRET; thus, the fluorescence from EDC can be enhanced effectively from both of excitation and emission processes on heterostructure PC array. Besides, high-resolution of single-base mutation was obtained through the strict recognition of EDC. Benefiting from the specific spectrum-matched and synergetic amplification of heterostructure PC and EDC with "DD-A" FRET, the proposed array obtained ultrasensitive detection of ctDNA with LOD of 12.9 fM, and achieved the analysis of mutation frequency as low as 0.01%. Therefore, the proposed strategy has the advantages of simple operation, mild conditions (enzyme-free and isothermal), high-sensitivity, high-resolution and high-throughput analysis, showing potential in bioassay and clinical application.

Design and Performance of Dual Band Microstrip Nano-Fractal Patch Antenna

Design and Performance of Dual Band Microstrip Nano-Fractal Patch Antenna

Dual band beam steering antenna using branch line coupler network for higher band applications

Abstract A beam-steering fed array antenna has been proposed for radar and mm-Wave applications operating from 22.6 to 26.89 GHz and 30–45 GHz with B.W % of 17.34 % and 40 % respectively having size of 12.11 × 25.58 × 0.8 mm3 (0.96λo × 2.01λo × 0.06λo). For radar, this antenna covers 24.15 GHz as police radar, 24.25–25.25 GHz & 31.8–33.4 GHz as navigation radar, and 33.4–36 GHz as high-resolution radar for airport surveillance. This antenna also covers mm-wave bands for different countries (Brazil-40 GHz, China- 34–42.5 GHz, Mexico- 33 GHz and 37 GHz, and USA- 24 GHz, 37 & 39 GHz). At initial stage, a monopole antenna with DGS has been designed with an operating band of 20.2–31.2 GHz and 36.6–42.2 GHz. Proposed antenna shifts the beam pattern at 90° with each other after exciting each port in alternative order with a scanning angle of ±45°, ±75° & ±180°. Peak gain for 1st band ranges from 7.1 to 9 dBi and for the 2nd band ranges from 8.8 to 10.2 dBi and has a radiation efficiency of 88 %. Other diversity parameters such as ECC, DG, MEG, and isolation get analysed to observe the coupling effects. Design, development, and analysis of all antenna parameters is done by using HFSS 19 platform.

Metasurface loaded dual band antenna for high gain on- and off- body communication

Metasurfaces are specially made materials designed to have unique properties not found in nature. They are categorized into different types, such as artificial magnetic conductor (AMC), partial reflecting surfaces (PRS), and frequency selective surfaces (FSS). Among these, FSS is commonly used in today’s technology to improve antenna performance, especially in boosting signal strength by blocking unwanted radiation. Recent research is focused on creating FSS-based antennas for Ultra-wideband (UWB) or single band applications, with a significant emphasis on enhancing signal strength. Unlike traditional methods, this study concentrates on designing antennas that are both simple in shape and offers broader frequency coverage, specifically for 2.45 GHz and 5.8 GHz applications. To enhance antenna performance, a dual-band FSS is employed, optimizing the system for improved operation at both resonating frequencies. This results in a high-gain antenna system, which is further investigated for body area network (BAN) systems, considering the crucial performance metric of specific absorption rate (SAR). The findings are compared with recently reported FSS-based antennas to underscore their scientific contribution and potential for high gain, low SAR applications within the 2.45 GHz and 5.8 GHz frequency bands.

Compact on-chip dual-band bandpass filter with wide out-of-band suppression based on hybrid coupling technique

A compact dual-band bandpass filter (BPF) with wide out-of-band suppression based on a hybrid coupling technique is proposed. This BPF consists of two hybrid spiral coupled resonators, in which the electrical coupling and magnetic coupling between resonators can generate two transmission paths for dual bands. This dual-band BPF has wide out-of-band suppression. Moreover, its passband frequency and bandwidth can be readily controlled. To illustrate its working principle, an equivalent circuit with even- and odd-mode analysis is presented. This dual-band BPF is fabricated using a silicon integrated passive device (IPD) technology. The fabricated dual-band BPF has a compact size of 1.6 mm × 0.54 mm × 0.23 mm and is measured. The measured results show that this dual-band BPF can generate two bands at 2.45 GHz and 6.15 GHz. In addition, more than 20 dB of suppression is achieved from 7.8 to 20 GHz (8.16f0). The simulated and measured results exhibit good agreements.

Tunable Near-Field Radiative Heat Transfer between Graphene-Coated Magneto-Optical Metasurfaces.

The highly structured design of metasurfaces greatly facilitates the manipulation of near-field radiative heat transfer (NFRHT). In this study, we incorporate magneto-optical materials into metasurfaces to theoretically explore the mechanism for controlling NFRHT between anisotropic magneto-optical metasurfaces. Our findings indicate that the interaction between the magnetization-induced modes, arising from interband transitions of graphene, and the surface modes of InSb under a magnetic field leads to a transition in the heat transfer spectrum from a dual band to a triple band. The modification of the distribution and magnitude of transmission wave vectors in surface electromagnetic modes by magnetic fields serves to modulate the radiative heat flux. By combining active control by a magnetic field with passive structural design of metasurfaces, the regulation of heat flux can be increased by more than 8-fold compared with the planar configuration. Additionally, the magnetic field amplifies the anisotropy of the photon energy distribution induced by the symmetry breaking of the metasurface structure. This study is anticipated to provide a pathway for achieving flexible tuning of NFRHT by combining active and passive regulation. It also opens up possibilities for multiband information transmission and for improving the performance of energy conversion devices.

Quadrupole mode plasmon resonance enabled dual-band metamaterial for refractive index sensing application

In this paper, design and fabrication of a dual-band near-zero index metamaterial (MTM) structure using copper on an epoxy resin fiber (FR-4) dielectric substrate is reported for refractive index sensing applications. The primary objective is to achieve dual-band operation spanning a 1–15 GHz frequency range, with a specific focus on achieving a broad bandwidth in the C-band. The resonance of the MTM structure was ascribed to the coupling of plane electromagnetic waves with surface plasmon polaritons on the structure, resulting in a quadrupole plasmon resonance mode. Furthermore, transmission characteristics of the fabricated MTM structure were experimentally measured and found to align closely with the simulated results obtained through the finite element method in COMSOL Multiphysics. The designed MTM structure demonstrates negative and near-zero permittivity at resonance frequencies, enabling left-handed and near-zero index behavior in dual microwave frequency bands. Under room temperature conditions, the MTM sensor exhibited sensitivities of 1 GHz/RIU and 3 GHz/RIU at resonance frequencies of 2.7 and 7.3 GHz, respectively. Consequently, the MTM structure exhibits significant potential for diverse applications, serving as a valuable component in sensors, detectors, and optoelectronic devices operating in the GHz region.

Dual band high tuning range frequency reconfigurable dielectric resonator antenna for sub-6 GHz applications

ABSTRACT A high-tuning range frequency reconfigurable dual-band compact cylindrical Dielectric Resonator Antenna (DRA) for 5 G Sub 6 GHz applications is presented in the proposed work. The work presented here provides compactness, frequency reconfigurability (FR), and dual-band. FR is obtained through two PIN diode switches, which operate in ON-ON, ON-OFF, OFF-ON, and OFF-OFF configurations and offer a maximum wide tuning range and a total spectrum of 44.44% and 71.49%, respectively. In the cylindrical DRA, the HE M 11 δ and HE M 12 δ modes create dual-band, while the hybrid structure and higher order mode excitation yield compactness.

Label -free measuring biomolecular interactions using plasmonic metasurfaces with dual bands based on surface lattice resonances in the mid-infrared range

Mid-infrared plasmonic metasurfaces are remarkable platforms for chemical-specific detection and dynamic monitoring of biomolecules. This study uses surface-enhanced infrared absorption (SEIRA) spectroscopy by applying plasmonic metasurfaces for label-free and real-time monitoring of biomolecular interactions. SEIRA devices based on geometric combinations of two types of square arrays with different Au microdots require the use of new dual-resonant plasmonic metasurfaces. Resonant matching between the plasmonic and molecular vibrational modes can be realized through the controlled microdot dimensions and periodicity of the array. Plasmonic surface lattice resonances contribute to this optical tuning, enabling simultaneous observations of SEIRA-enhanced methyl and amide bands. The electric fields on mixed arrays were strongly confined to approximately 100 nm, enabling high SEIRA performance and single molecule detection. Moreover, the SEIRA device no longer needed in-plane polarization control of IR light, enhancing sensing detection’s robustness and stability. Finally, the in situ real-time monitoring of biomolecular interactions between protein A and immunoglobulin, which provides remarkable changes in the intensity and vibrational features of SEIRA absorbance, is reported. Dynamic SEIRA measurements using molecular vibrations as self-biomarkers helped in identifying the kinetic parameters required for important affinity metrics of biomolecular interactions.

Dual Hole Transport Layers Heterojunction and Band Alignment Engineered Mo:BiVO4 Photoanodes for Efficient Water Splitting.

BiVO4-based photoanode is one of the most promising photoanodes for photoelectrocatalytic water splitting. However, the serious problem of interface charge recombination limits its further development. Here, a Mo:BiVO4/NiOx/CPF-TCzB/NiCoBi photoanode is constructed with double hole transport layer and an energy level gradient to achieve an effective photo-generated holes extraction and accumulation at the surface electrocatalyst. The conjugated polycarbazole framework CPF-TCzB is used as hole transport layer to eliminate the charge recombination center between Mo:BiVO4 and NiCoBi electrocatalyst and realize the extraction and storage of photo-generated hole; NiOx nanoparticles are further inserted between Mo:BiVO4 and CPF-TCzB to form a gradient energy level, eliminating the energy level barrier and optimizing band alignment. As a result, Mo:BiVO4/NiOx/CPF-TCzB/NiCoBi achieves a much higher photocurrent densities of 3.14mA cm-2 than that of Mo:BiVO4 (0.42mA cm-2) at 0.6V versus RHE. This work provides an specific way to adjust the band structure of BiVO4-based photoanodes and realize efficient hole extraction and storage for PEC water splitting.