Narrow Bandwidth Research Articles

Cellular Internet of Things: Principles, Potentials and Use Cases

Internet of things (IoT) can either be deployed over existing cellular networks or their own custom-built standalone networks. Based on the infrastructure, IoT can be classified into two types: cellular and non-cellular categories. In the cellular form, IoT network needs the support of cellular infrastructure of the mobile service providers. Currently, three forms of cellular IoT are being deployed across the world. They are: narrowband Internet of things (NBIoT), extended coverage GSM (EC-GSM) and long term evolution for machines (LTE-M). Out of these three, NBIoT and EC-GSM are low energy and low resource consuming versions of cellular IoT. They need narrow bandwidths for their operations. Their energy consumption is also very low and thus suitable for low energy applications. Both NBIoT and EC-GSM are compatible with all types of cellular communication infrastructure such as 2G, 3G, 4G and 5G. They can cover a large area with a very small amount of power. Both these forms are popular low power wide area (LPWA) technologies. Due to their LPWA features, they are popular for the connected living applications at home and workplace surroundings. Their LPWA features make them popular green technology for digital transformation. LTE-M uses comparatively larger bandwidth and higher power. It is suitable for higher bandwidth and higher data rate applications. We survey the recent literature on cellular IoT and present their key principles, potentials and applications. We provide their main characteristics, deployment options, standards, and some specific applications in different sectors.

All-Dielectric Dual-Band Anisotropic Zero-Index Materials

Zero-index materials, characterized by near-zero permittivity and/or permeability, represent a distinctive class of materials that exhibit a range of novel physical phenomena and have potential for various advanced applications. However, conventional zero-index materials are often hindered by constraints such as narrow bandwidth and significant material loss at high frequencies. Here, we numerically demonstrate a scheme for realizing low-loss all-dielectric dual-band anisotropic zero-index materials utilizing three-dimensional terahertz silicon photonic crystals. The designed silicon photonic crystal supports dual semi-Dirac cones with linear-parabolic dispersions at two distinct frequencies, functioning as an effective double-zero material along two specific propagation directions and as an impedance-mismatched single-zero material along the orthogonal direction at the two frequencies. Highly anisotropic wave transport properties arising from the unique dispersion and extreme anisotropy are further demonstrated. Our findings not only show a novel methodology for achieving low-loss zero-index materials with expanded operational frequencies but also open up promising avenues for advanced electromagnetic wave manipulation.

One-Dimensional Photonic Crystals Comprising Two Different Types of Metamaterials for the Simple Detection of Fat Concentrations in Milk Samples

In this study, we demonstrate the reflectance spectrum of one-dimensional photonic crystals comprising two different types of metamaterials. In this regard, the designed structure can act as a simple and efficient detector for fat concentrations in milk samples. Here, the hyperbolic and gyroidal metamaterials represent the two types of metamaterials that are stacked together to construct the candidate structure; meanwhile, the designed 1D PCs can be simply configured as [G(ED)m]S. Here, G refers to the gyroidal metamaterial layers in which Ag is designed in a gyroidal configuration form inside a hosting medium of TiO2. In contrast, (ED) defines a single unit cell of the hyperbolic metamaterials in which two layers of porous SiC (E) and Ag (D) are combined together. It is worth noting that our theoretical and simulation methodology is essentially based on the effective medium theory, characteristic matrix method, Drude model, Bruggeman’s approximation, and Sellmeier formula. Accordingly, the numerical findings demonstrate the emergence of three resonant peaks at a specified wavelength between 0.8 μm and 3.5 μm. In this context, the first peak located at 1.025 μm represents the optimal one regarding the detection of fat concentrations in milk samples due to its low reflectivity and narrow full bandwidth. Accordingly, the candidate detector could provide a relatively high sensitivity of 3864 nm/RIU based on the optimal values of the different parameters. Finally, we believe that the proposed sensor may be more efficient compared to other counterparts in monitoring different concentrations of liquid, similar to fats in milk.

THz Biosensing for Early Detection of Influenza and Coronaviruses Using Dielectric Metamaterials

Abstract The world has faced a significant challenge since December 2019, when coronavirus (COVID-19) was found. Viruses of this type are causing pandemics all over the world right now. For this purpose, a biosensor is designed to operate based on metamaterial (MM) incorporated and can detect different coronaviruses. The proposed metamaterial absorber (MMA) includes two bands that have perfect absorption characteristics and a very narrow absorption bandwidth: 4.093 THz and 3.647 THz. The circuit model's transmission line technique is another approach to verifying the absorber's functionality. The proposed design consists of a square-shaped graphene ring (SGR) and a silicon-based square ring resonator (SSRR) to provide unique and narrow band absorption characteristics. Changing the graphene’s chemical potential gives the suggested MMA tuneability and control capability. The suggested MMA can detect several coronaviruses because of its extremely narrow absorption spectrum behavior. It has unique features such as ultra-narrow absorption bandwidth, polarization insensitivity, and simplicity. The MMA is designed with a compact structure, good sensitivity (s), exceptional Figure of Merit (FOM), and superior Quality factor (Q) values.

Dual-emissive carbon dots with high-color purity from sweet basil leaves: synthesis, characterization and optical properties

Abstract In this study, we synthesized dual-emission carbon dots (CDs) from sweet basil leaves dissolved in hexane using the hydrothermal method. Extensive analyses were carried out on their morphology, structure, and optical properties. The CDs show a spherical shape and highly disordered structure with an average diameter of 2 nm. They predominantly comprise carbon surrounded by a dense shell layer of oxygen and nitrogen-related functional groups. Under excitation at a single wavelength of 380 nm, the CDs emit two distinct peaks at 450 and 675 nm demonstrating a narrow bandwidth emission with full width at half maximum (FWHM) of 72 and 27 nm, respectively. The emission characteristics of the CDs are ascribed to the combined effects of radiative recombination of the carbon-core and fully passivated surface states, resulting in two distinct emission peaks and excitation-independent emission property. We present a highly effective and eco-friendly approach approach to fabricate luminescent CDs exhibiting dual emission properties derived from sustainable resources, holding promise for utilization in bioimaging.

Solvent mediated synthesis of multicolor narrow bandwidth emissive carbon quantum dots and their potential in white light emitting diodes

The development of efficient and environmentally sustainable materials for white light-emitting diodes (WLEDs) is of paramount importance in the field of lighting technology. In this study, we present a solvent-modulated synthesis approach for the fabrication of multicolor narrow-bandwidth emissive carbon quantum dots (CQDs) as a promising solution for constructing WLEDs. The synthesis method involves the controlled reaction of organic precursors in different solvent environments, leading to the formation of CQDs with distinct emission wavelengths with a relatively small full width at half maximum, ranging from 28 to 42 nm. Moreover, these synthesized multicolor CQDs demonstrate a remarkably high fluorescence quantum yield of up to 65%, indicating their potential for constructing efficient WLED when incorporated in polymer matrix and coated on the surface of blue light-emitting diode (LED).

Performance Analysis and Prediction of 5G Round-Trip Time Based on the VMD-LSTM Method

With the increasing level of industrial informatization, massive industrial data require real-time and high-fidelity wireless transmission. Although some industrial wireless network protocols have been designed over the last few decades, most of them have limited coverage and narrow bandwidth. They cannot always ensure the certainty of information transmission, making it especially difficult to meet the requirements of low latency in industrial manufacturing fields. The 5G technology is characterized by a high transmission rate and low latency; therefore, it has good prospects in industrial applications. To apply 5G technology to factory environments with low latency requirements for data transmission, in this study, we analyze the statistical performance of the round-trip time (RTT) in a 5G-R15 communication system. The results indicate that the average value of 5G RTT is about 11 ms, which is less than the 25 ms of WIA-FA. We then consider 5G RTT data as a group of time series, utilizing the augmented Dickey–Fuller (ADF) test method to analyze the stability of the RTT data. We conclude that the RTT data are non-stationary. Therefore, firstly, the original 5G RTT series are subjected to first-order differencing to obtain differential sequences with stronger stationarity. Then, a time series analysis-based variational mode decomposition–long short-term memory (VMD-LSTM) method is proposed to separately predict each differential sequence. Finally, the predicted results are subjected to inverse difference to obtain the predicted value of 5G RTT, and a predictive error of 4.481% indicates that the method performs better than LSTM and other methods. The prediction results could be used to evaluate network performance based on business requirements, reduce the impact of instruction packet loss, and improve the robustness of control algorithms. The proposed early warning accuracy metrics for control issues can also be used to indicate when to retrain the model and to indicate the setting of the control cycle. The field of industrial control, especially in the manufacturing industry, which requires low latency, will benefit from this analysis. It should be noted that the above analysis and prediction methods are also applicable to the R16 and R17 versions.

Resonant Raman Auger spectroscopy on transient core-excited Ne ions

Abstract Short-lived core-ionized neon atoms were investigated by measuring under resonant Raman conditions the Auger decay following the excitation of a second core electron into a Rydberg state. Making use of intense and narrow bandwidth x-ray free-electron laser pulses, the photoexcitation spectrum of the femtosecond-lived Ne+1s02s22p6np series was characterized. Energy position and lifetimes of the lower-lying Rydberg states were determined and the final state configurations following the decay of the Ne+1s02s22p63p double-core hole resonance were partially resolved.

Performance Comparison of Seed Generation Techniques of Stimulated Brillouin Scattering-Based Microwave Photonics Amplifier and Filter

This work presents a Brillouin amplification performance comparison of seed generation techniques using double-sideband suppressed carrier (DSB-SC) and single-sideband suppressed carrier (SSB-SC) modulations. The SSB-SC is obtained using an optical bandpass filter (OBPF) and in-phase and quadrature Mach-Zehnder modulator (IQ-MZM). All three techniques provide high amplification performance with optical signal-to-noise ratio (OSNR) enhancement of 37.47 dB, 33.14 dB, and 32.67 dB using DSB-SC, SSB-SC/OBPF, and SSB-SC/IQ-MZM, respectively. The best seed generation technique is using the DSB with a signal amplification of 62.47 dB. The technique presents ~4 dB higher OSNR enhancement due to the dual-energy transfer obtained from the beating process of the DSB than SSB. A ~3 dB OSNR reduction is found when pump linewidth (LW) was changed from 1kHz to 50 MHz, which suggests using a low-cost pump source whenever the OSNR reduction is not critical. The work also shows that the three techniques required 10 dBm stimulated Brillouin scattering threshold (SBST) to stimulate the process. An additional analysis of DSB-SC shows that a high-carrier suppression during the seed generation technique using MZMs is insignificant to the amplification performance. The high-carrier suppression produces a high seed signal power that distorts the Brillouin gain spectrum (BGS) and the pump depletion region, hence reducing the Brillouin gain (BG). Since carrier suppression is not a primary consideration, a cost-effective MZM with a modest extinction ratio requirement is allowed. The relaxed requirement of the pump’s linewidth and MZM’s extinction ratio suggest a cost-effective development of the SBS-based optical amplifier with narrow filter bandwidth.

Rectangular Slot based Beam Focusing Dual-Band Phase Gradient Metasurface

This study proposes method for enhancing the performance of previously developed or produced weapon systems without developing new detection equipment by using Phase Gradient Metasurfaces(PGMS). Metasurface has been studied and utilized a lot to improve the detection performance of inorganic systems, but its utilization is low due to its narrow bandwidth and complex structure. To address some of these limitations, dual-band power focusing PGMS is proposed. Its frequency independent unit cell characteristic enables creating metasurface that concentrates signals in dual-band. The designed PGMS was validated through near-field and far-field measurement, confirming signal concentration at the specified focal length and improved gain in the dual bands.

Achromatic Full Stokes Polarimetry Metasurface for Full-Color Polarization Imaging in the Visible Range.

Metasurfaces provide an ultrathin platform for compact, real-time polarimetry. However, their applications in polychromatic scenes are restricted by narrow operating bandwidths that causes spectral information loss. Here, we demonstrate full-color polarization imaging using an achromatic polarimeter consisting of four polarization-dependent metalenses. Leveraging an intelligent design scheme, we achieve effective arbitrary phase compensation and multiobjective matching with a limited database. This system provides broadband achromaticity across wavelengths from 450 to 650 nm, resulting in a relative bandwidth of approximately 0.364 for full Stokes imaging. Experimental reconstruction errors for wavelengths of 450, 550, and 650 nm are 7.5%, 5.9%, and 3.8%, respectively. Performance is evaluated based on both achromatic bandwidth and crosstalk, with our design achieving three times the performance of the current state-of-the-art. The full-color, full-polarization imaging capability of the device is further validated with a customized object. The proposed scheme advances polarization imaging for practical applications.

Merging of quasi-bound states in the continuum and Wood anomalies in terahertz metasurfaces based on complementary periodic cross-shaped resonators

Metasurfaces provide an ideal platform for controlling the merging of multiple modes owing to trimmable periodic meta-atoms. In this work, a terahertz metasurface based on complementary periodic cross-shaped resonators (CPCRs) with mixed modes is demonstrated. The CPCRs support sharp quasi-bound states in the continuum (quasi-BICs) by introducing an offset parameter. The optical response of quasi-BICs such as frequency shift and Q-factor can be optimized by tuning offset parameters. As such parameter increases, a mixed mode originating from quasi-BICs and Wood anomalies appears. The merged resonance has a narrow bandwidth with steep edges and thus can serve as bandpass filters. Simulated electric field distributions reveal the special patterns for these modes. Owing to the effect of quasi-BICs, Wood anomalies exhibit different field patterns in contrast to those of pure modes. These results prove the possibility of multimode merging in metallic metasurfaces, which is beneficial for terahertz applications such as sensing and wave filters.

The Origins of Narrow Spectra of Fast Radio Bursts

Observations find that some fast radio bursts (FRBs) have extremely narrowband spectra, i.e., Δν/ν 0 ≪ 1. We show that, when the angular size of the emission region is larger than the Doppler beaming angle, the observed spectral width (Δν/ν 0) exceeds 0.58 due to the high-latitude effects for a source outside the magnetosphere, even when the spectrum in the source’s comoving frame is monochromatic. The angular size of the source for magnetospheric models of FRBs can be smaller than the Doppler beaming angle, in which case this geometric effect does not influence the observed bandwidth. We discuss various propagation effects to determine if any could transform a broad-spectrum radio pulse into a narrow spectrum signal at the observer’s location. We find that plasma lensing and scintillation can result in a narrow bandwidth in the observed spectrum. However, the likelihood of these phenomena being responsible for the narrow observed spectra with Δν/ν 0 < 0.58 in the fairly large observed sample of FRBs is exceedingly small.

Stimulated Brillouin scattering in silica optical nanofibers

Stimulated Brillouin scattering offers a broad range of applications, including lasers, sensors, and microwave photonics, most of which require strong Brillouin gain within a narrow bandwidth. Here, we experimentally report the first measurement of stimulated Brillouin scattering in silica optical nanofibers from both hybrid and surface acoustic waves. Using a pump–probe technique in the radio frequency domain, we measured a Brillouin gain as high as 15 m−1 W−1 and linewidth to 16 MHz for the L03 hybrid acoustic mode near 9 GHz using a 990-nm diameter nanofiber. This gain is 65 times larger than the highest gain obtained in standard single-mode fibers. In addition, we report a Brillouin gain of up to 5 m−1 W−1 from surface acoustic waves around 5 GHz. We further demonstrate a nanofiber-based Brillouin laser with a threshold of 350 mW. Our results create opportunities for advanced Brillouin-based applications utilizing optical nanofibers.

Coherent Radio Emission from “Main-sequence Radio Pulse Emitters”: A New Stellar Diagnostic to Probe 3D Magnetospheric Structures

Main-sequence radio pulse emitters (MRPs) are magnetic early-type stars that produce coherent radio emission observed in the form of periodic radio pulses. The emission mechanism behind this is the electron-cyclotron maser emission (ECME). Among all kinds of magnetospheric emission, ECME is unique due to its high directivity and intrinsically narrow bandwidth. The emission is also highly circularly polarized and the sign of polarization is opposite for the two magnetic hemispheres. This combination of properties makes ECME highly sensitive to the three-dimensional structures in the stellar magnetospheres. This is especially significant for late-B and A-type magnetic stars that do not emit other types of magnetospheric emission such as Hα, the key probe used to trace magnetospheric densities. In this paper, we use an ultra-wideband observation (0.4–2 GHz) of a late B-type MRP HD 133880 to demonstrate how we can extract information on plasma distribution from ECME. We achieve this by examining the differences in pulse arrival times (“lags”) as a function of frequencies and qualitatively comparing those with lags obtained by simulating ECME ray paths in hot stars’ magnetospheres. This reveals that the stellar magnetosphere has a disk-like overdensity inclined to the magnetic equator with a centrally concentrated density that primarily affects the intermediate frequencies (400–800 MHz). This result, which is consistent with the recent density model proposed for hotter centrifugally supported magnetospheres, lends support to the idea of a unifying model for magnetospheric operations in early-type stars, and also provides further motivation to fully characterize the ECME phenomenon in large-scale stellar magnetospheres.

A low-profile Wideband Meta-Surface based Microstrip Antenna for 5G Wireless Communications

This article presents a low-profile meta surface microstrip radiator operating at 34GHz with high performance for the operation of 5G wireless communications. The meta-surface radiator entails an improved patch that is present between the 4×4 proportioned square ring meta-surface and a ground plane. Initially, the rectangular slot of the patch would be aligned to improve the inherent narrow bandwidth. But the multifunctional properties of the proposed meta surface antenna with a convinced operating frequency increases the functionality and size of the network. Moreover, this paper outlines how the unit cell meta surface is implemented as a superstrate with a single U-slot for a rectangular patch antenna. The proposed antenna is simulated and measured on FR4 epoxy substrate material with a modified patch with a specific air-gap yields an overall antenna size of 1.36λ0×1.36λ0×0.1818λ0 especially to operate at 34 GHz resonating frequency. The results demonstrate that the meta surface radiator can achieve a wide-bandwidth range from 28 to 41GHz for S11 with a return loss of 60dB along with a maximum valued gain of 10dBi with a 3dB AR bandwidth.

Low noise signal processing for electrochemical biosensor using narrow bandwidth filter

Abstract Biosensor has an important role in several domains, including medical and environmental applications. The improvement of biosensor measurement system therefore offers a better measurement quality. The objective of this work is the development of the signal processing of electrochemical biosensor for advanced analysis and use. The noise of electrochemical sensor is considered rather higher than the other sensor due to many factors such as electrode area, solution velocity, and particle size in solution, which affect adsorption-desorption process. Moreover, the sensor signal processing also makes contribution to noise level. Therefore, it must be reduced and suppressed to obtain better measurement result. In this paper, a bandwidth optimisation method is proposed and used to improve measurement quality. The system is realized with a transimpedance circuit and low-pass and high-pass filter, so that it offers low noise characteristics. The developed proposed system has provided better improvement than the standard electrochemical biosensor system. The noise of the system can be suppressed to be lower up to 14.3% of the standard transimpedance circuit. This development is promising to give better biosensor measurement.

Quantum jump photodetector for narrowband photon counting with a single atom

Using a single neutral Rb87 atom held in an optical trap, and “quantum jump” detection of single-photon-initiated state changes, we demonstrate a single-photon quantum jump photodetector (QJPD) with intrinsically narrow bandwidth and strong rejection of out-of-band photons, of interest for detecting weak optical signals in the presence of a strong broadband background. By analyzing fluorescence photon count distributions for the bright and dark states with and without excitation, we measure quantum efficiency of 2.9(2)×10−3, a record for single-pass quantum jump production, and signal-photon-unprovoked “dark jump” rate—analogous to the dark count rate of other detectors —of 3(10)×10−3jumps/s during passive accumulation plus 4.0(4)×10−3 jumps per readout, orders of magnitude below those of traditional single-photon detectors. Available methods can substantially improve QJPD quantum efficiency, dark jump rate, bandwidth, and tunability. Published by the American Physical Society 2024

Assessment of spectral ghost artifacts in echo-planar spectroscopic micro-imaging with flyback readout

In this work, echo-planar spectroscopic imaging (EPSI) with flyback readout gradient-echo train was implemented in a preclinical MR scanner. The aim of this study is to visualize and quantify the ghost spectral lines produced by two, three and four interleaved echo trains with different amplitudes of the readout gradients, and to investigate the feasibility of the flyback data acquisition in micro-imaging of small animals. Applied multi-slice EPSI sequence utilizes asymmetric gradient-echo train that combines the shortest possible rewind gradients with readout gradients. It simplifies data processing because all echoes are acquired with the same polarity of the readout gradient. The approach with four interleaved gradient-echo trains and with four echoes in each train provides broad spectral bandwidth in combination with narrow receiver bandwidth and a good water-fat signal separation. It improves signal-to-noise ratio without the undesired consequence of water-fat shift artifacts that are eliminated during data processing. Position, number, and intensity of the ghost spectral lines can be controlled by the suitable choice of spectral bandwidth, number of echo train interleaves, and the number of echoes in each interleave. This study demonstrates that high-spatial resolution EPSI with interleaved flyback readout gradient-echo trains is feasible on standard preclinical scanners.

Research on Drug Efficacy using a Terahertz Metasurface Microfluidic Biosensor Based on Fano Resonance Effect.

Advanced biosensors must exhibit high sensitivity, reliability, and convenience, making them suitable for detecting trace samples in biological or medical applications. Currently, biometric identification is the predominant method in clinical practice, but it is complex and time-consuming. In this study, we propose an optical metasurface utilizing the Fano resonance effect, which exhibits a sharp resonance with a transmittance of 32% at 0.65 THz. The resonance dip has a narrow bandwidth of 0.07 THz and a high Q-factor of 42. This resonance arises from the coupling of bright and dark modes, underpinned by the electromagnetic mechanism of Fano resonance. We integrated the metasurface into a microfluidic platform and fabricated low-temperature gallium arsenide photoconductive antennas (LT-GaAs-PCAs) on both sides of the microfluidics to efficiently generate and detect THz waves, significantly reducing the system's volume. The biosensor's detection limits for Escherichia coli (E. coli) and cefamandole nafate are 5 × 103 cells/mL and 5 μg/mL, respectively. Experimentally, when E. coli and cefamandole nafate solutions were sequentially injected into the microfluidic chip, a blue shift in the spectrum was observed. The sensor measured a 95.2% killing rate of E. coli by 40 μg/mL cefamandole nafate solution, with only a 3% deviation from biological experiments. Additionally, a timed killing experiment using 40 μg/mL cefamandole nafate on E. coli revealed a 93.7% killing rate within 3 min. This research presents a THz microfluidic biosensor with rapid detection, high sensitivity, and enhanced portability and integration, offering a promising approach for biomedical research, including antibiotic efficacy assessment and bacterial concentration monitoring.