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In this paper, a wideband polarization reconfigurable omnidirectional antenna (PROA) based on a single-substrate active metasurface is proposed. By controlling the states of the PIN diodes, the antenna can selectively radiate an omnidirectional linearly polarized wave and an omnidirectional circularly polarized wave. The reflection coefficient, axial ratio (AR), radiation pattern, and gain of the proposed antenna have been analyzed from the perspective of simulation and measurement. The measured results show that the PROA has a wide overlapped bandwidth from 2.87 to 3.67 GHz (relative bandwidth 24.46%). To the authors' best knowledge, this is the first reported wideband PROA based on a single-substrate reconfigurable polarization converter. This study not only offers a novel approach to design PROAs, but also greatly reduces the design complexity of the feed source compared with the traditional design method of PROAs. [ABSTRACT FROM AUTHOR]

Purcell filters, which serve to suppress electromagnetic radiation and enhance the readout efficiency of qubit, are an indispensable component in superconducting quantum chips. With the increasing scale of quantum chips, the requirements for the performance and scalability of Purcell filters are becoming more stringent. In this report, a novel four-stage Purcell filter that enables fast measurement without exacerbating environmental damping of the qubits is presented. The design approach of the filter is derived from the serial and parallel configurations of λ/4 resonant cavities. The filter exhibits exceptional passband-to-stopband isolation, reaching up to 40 dB of isolation within the transition range of 400 MHz. Furthermore, the filter boasts a wide bandwidth for both the stopband and the passband, with the stopband ranging from 4 to 5.5 GHz and the passband extending from 5.8 to 6.5 GHz. In terms of spatial arrangement, each filter can be connected to over ten readout resonators for qubit readout. This innovative Purcell filter will significantly contribute to the development of high quality, scalable superconducting quantum chips. [ABSTRACT FROM AUTHOR]

Realization of microwave-absorbing materials with "small thickness, light weight, broad bandwidth, and low reflectivity" is an invariable topic. In this paper, Sm2Fe14BHx/polyurethane (SFBH/PU) composites with planar anisotropy were prepared by reduction–diffusion (R/D) and water bath hydrogenation (WBH) process. A minimum reflection loss (RL) value reaches −59.7 dB at the perfect matching frequency of 13.79 GHz with a thickness of only 1.035 mm. Compared with unhydrogenated SFB, the bandwidth and reflectivity are significantly improved. It is mainly attributed to the fact that introduction of hydrogen atoms effectively modulates the electromagnetic parameters and increases the Snoek limit ((μ i − 1) f r) , which leads to the improvement of the high-frequency microwave absorption performance. In addition, the bandwidth equation is derived and simplified from the perspective of the reflected wave at the interface, which is in good agreement with the measured results. [ABSTRACT FROM AUTHOR]

Acoustic asymmetric focusing (AAF) has attracted widespread attention owing to its great potential in medical ultrasound. The recent development of acoustic metamaterials and metasurfaces has provided various concepts to achieve AAF systems. Generally, the previously demonstrated AAF lenses were limited to one-dimensional structures, leading to difficulties in practical applications. The realization of AAF in three-dimensional (3D) space based on a two-dimensional (2D) device still remains a challenge. Here, we experimentally and numerically study a 2D AAF lens based on mode converters composed of two pairs of phased unit cells I and II and a step waveguide. Based on the phase profile of sound focusing and the step waveguide of mode converters, we experimentally design and demonstrate a type of 2D AAF lens and observe acoustic focusing and asymmetric transmission simultaneously in 3D space under the excitation of the zero-order wave. Both the phenomena arise from the phase modulation of the lens and the cutoff frequency of the first-order wave for the step waveguide, respectively. The fractional bandwidth (the ratio of the bandwidth to the center frequency) of the lens can reach about 0.14. The proposed 2D AAF lens, as well as its associated mode converter, paves the way for the asymmetric manipulation of sound in 3D space that has potential applications in practical sound devices. [ABSTRACT FROM AUTHOR]

Frustrated lattices with dispersionless band structures and fully localized states are an exciting platform for exploring many-body physics. In this work, we identify X 3 MnN 3 (X = Ca, Sr, Ba) as a frustrated lattice and investigate its physical properties in the ferromagnetic (FM) and antiferromagnetic (AFM) states based on first-principles calculations. Our results show that all three materials in FM and A-type AFM configurations have flatbands with band touching in the k z ∼ 0 and k z ∼ π planes with bandwidths less than 0.2 eV. Intriguingly, the flatband is tuned to the Fermi level when X 3 MnN 3 is transformed into the FM state. Furthermore, we find the two-dimensional dice model hidden in X 3 MnN 3 by treating the coupled Mn and N atoms as a basic site, revealing that the compact localized state is generated by destructive interferences between the hopping amplitudes, and the dice models stack the system staggered along the c -axis. Our work provides new candidate materials for exploring strong correlation physics and reveals the mechanism of their localized state. [ABSTRACT FROM AUTHOR]

Machine learning has been used to accelerate studies in the dynamics of optical pulses. In this study, we use machine learning to investigate the optimal design of supercontinuum-generating hollow-core antiresonant fibers (HC-ARFs) pressurized and filled with methane. Artificial neural networks (ANNs) are trained to replace the numerical solvers, accelerate the simulation of fibers, and provide a more rapid fiber design procedure. We first use an analytical model to approximate the dispersion and loss of the methane-filled silica HC-ARF. This approximation is used by the generalized unidirectional pulse propagation equation solver to simulate the pulse propagation and generate training data for our ANNs by varying design parameters including the pump center wavelength, fiber hollow-core radius, fiber length, cladding strut thickness, and gas pressure. We evaluate the performance of different spectral-predicting ANN architectures and use the trained ANN along with a custom fiber performance function to search the full parameter space. Subsequently, the regions with design parameters with predicted high performance are identified, and these high-performance HC-ARF designs are further optimized for supercontinuum generation at target supercontinuum bandwidths. We also extend our effort to maximizing the total spectral energy outside of the input pump wavelength by integrating the ANN with a global optimization technique for the search of an optimal HC-ARF design. [ABSTRACT FROM AUTHOR]

A design method to extend the operating bandwidth of a low-frequency magnetic microwave absorber is presented. According to the mapped impedance distribution from the design objective, a synthesized reactive ground consisting of a triple-ring array, instead of the perfect electric conductor (PEC), is conveniently placed at the back of a commercially available magnetic sheet to realize impedance matching. Compared with the conventional PEC, the reactive ground extends the operating bandwidth of reflection coefficient being less than −10 dB by introducing four consecutive absorption peaks so that the optimized structure achieves broadband absorption from 2.3 to 4.3 GHz with a thickness of 0.027 times the free-space wavelength at the lowest operating frequency and a 60.6% fractional bandwidth which is nearly two times that of the conventional structure. The physical mechanism is further investigated through the distributions of current flow and power loss. Finally, a prototype is fabricated and measured. The good agreement between the simulated and measured results verifies the effectiveness of the presented design method. [ABSTRACT FROM AUTHOR]

A Transimpedance amplifier (TIA)-based optical receiver in active voltage-current feedback topology is designed for optical interconnects at 0.18 μ m CMOS technology. The proposed inductorless TIA incorporates a gain boosting amplifier in its path to achieve high gain and bandwidth. This gain boosting amplifier is based on a regulated gain cascode (RGC) amplifier. The RGC stage raises the g m of the circuit, reducing the input resistance of the input stage; as a result, the bandwidth extends. To further amplify the gain, a common source (CS) stage is used at the output without much effect on the system's overall bandwidth. An analytical model of the proposed TIA is developed and later simulated at room temperature in the Cadence Virtuoso analog design environment. The pre-layout and post-layout simulation results of the proposed TIA have been shown to validate its performance. It achieves a transimpedance gain of 62 d B Ω while consuming power of 14.5 mW from a 1.8 V supply voltage. The bandwidth is extended to 8.2 GHz from 1.83 GHz with an input photodiode capacitance of 300 fF. The current spectral density of input-referred noise is 31 pA/ H z. [ABSTRACT FROM AUTHOR]

This work presents a tunable receiver analog front-end (AFE) circuit, capable of achieving data rates between 14 Gb/s and 28 Gb/s. The circuit is implemented using the TSMC 65 nm CMOS technology. The circuit incorporates a continuous-time linear equalizer (CTLE), a transimpedance amplifier (TIA) and an output buffer. A g m -boosted technique is employed within the CTLE for bandwidth and gain enhancement, while the TIA leverages a super source follower (SSF) structure to combat parasitic output node issues. By adjusting the tunable structures in the circuit, the proposed AFE can achieve variable DC gain at 14 GHz. Simulation results reveal that the AFE can compensate for the channel loss at the 14 GHz Nyquist frequency, delivering eye diagram spreads of approximately 0.85 UI and 0.78 UI at 14 Gb/s and 28 Gb/s, respectively. The complete post-simulation layout area is only 0.0026 mm2. Operating with a power consumption of 10.5 mW, the AFE exhibits an exceptional FoM of 11.8 pJ/bit/dB. [ABSTRACT FROM AUTHOR]

Piezoelectric accelerometers excel in vibration sensing. In the emerging trend of fully organic electronic microsystems, polymeric piezoelectric accelerometers can be used as vital front-end components to capture dynamic signals, such as vocal vibrations in wearable speaking assistants for those with speaking difficulties. However, high-performance polymeric piezoelectric accelerometers suitable for such applications are rare. Piezoelectric organic compounds such as PVDF have inferior properties to their inorganic counterparts such as PZT. Consequently, most existing polymeric piezoelectric accelerometers have very unbalanced performance metrics. They often sacrifice resonance frequency and bandwidth for a flat-band sensitivity comparable to those of PZT-based accelerometers, leading to increased noise density and limited application potentials. In this study, a new polymeric piezoelectric accelerometer design to overcome the material limitations of PVDF is introduced. This new design aims to simultaneously achieve high sensitivity, broad bandwidth, and low noise. Five samples were manufactured and characterized, demonstrating an average sensitivity of 29.45 pC/g within a ± 10 g input range, a 5% flat band of 160 Hz, and an in-band noise density of 1.4 µg/ Hz . These results surpass those of many PZT-based piezoelectric accelerometers, showing the feasibility of achieving comprehensively high performance in polymeric piezoelectric accelerometers to increase their potential in novel applications such as organic microsystems. [ABSTRACT FROM AUTHOR]

We investigate three square-shaped antennas to increase the bandwidth of circular polarization. Each antenna has two adjacent corners excited with the same amplitudes and a phase difference of 90° using a branched feedline vertical to the ground plane. We evaluate the 3 dB axial ratio bandwidth as a function of the loop-arm width using the moment method. It is found that the axial ratio bandwidth reaches 38% for an arm width of 0.04 wavelengths, wider than that of a wire-loop antenna by a factor of three. The simulated results are verified by experimental ones. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) light sources have gained immense popularity in recent years due to their wide range of applications in various fields, including spectroscopy and biomedical imaging. However, the limited emission bandwidth of NIR phosphors is a significant bottleneck in their development. Here, a novel strategy is reported to broaden the emission bandwidth of NIR phosphors by awakening the dumb site. Na4M3Ta(PO4)6: Cr3+ (M = Al3+, Ga3+, In3+) phosphor is synthesized, which exhibits a greatly broadened bandwidth from 134 to 232 nm. Structural and spectral analysis reveals that the NaO6 octahedral site has a severe t2g‐type distortion, making it a dumb site for Cr3+. By introducing larger In3+ at the M site, the angular distortion at the NaO6 site decreases to the normal range, enabling the luminescence of Cr3+ again. Along with the broadened bandwidth, the emission peak also redshifts from 802 to 977 nm, giving advantages in NIR spectroscopy applications. Interestingly, the awakened luminescence at the NaO6 site shows even better luminescence properties than the original M/TaO6 octahedral site. These findings reveal a novel insight into the luminescence of Cr3+ at the octahedral site, which could potentially revolutionize the design of NIR phosphors. [ABSTRACT FROM AUTHOR]

The article presents the analysis, design, and low-cost implementation of application-specific AD converters for M-sequence-based UWB applications to minimize and integrate the whole UWB sensor system. Therefore, the main goal of this article is to integrate the AD converter's own design with the UWB analog part into the system-in-package (SiP) or directly into the system-on-a-chip (SoC), which cannot be implemented with commercial AD converters, or which would be disproportionately expensive. Based on the current and used UWB sensor system requirements, to achieve the maximum possible bandwidth in the proposed semiconductor technology, a parallel converter structure is designed and presented in this article. Moreover, 5-bit and 4-bit parallel flash AD converters were initially designed as part of the research and design of UWB M-sequence radar systems for specific applications, and are briefly introduced in this article. The requirements of the newly proposed specific UWB M-sequence systems were established based on the knowledge gained from these initial designs. After thorough testing and evaluation of the concept of the early proposed AD converters for these specific UWB M-sequence systems, the design of a new AD converter was initiated. After confirming sufficient characteristics based on the requirements of UWB M-sequence systems for specific applications, a 7-bit AD converter in low-cost 0.35 µm SiGe BiCMOS technology from AMS was designed, fabricated, and presented in this article. The proposed 7-bit AD converter achieves the following parameters: ENOB = 6.4 bits, SINAD = 38 dB, SFDR = 42 dBc, INL = ±2-bit LSB, and DNL = ±1.5 LSB. The maximum sampling rate reaches 1.4 Gs/s, the power consumption at 20 Ms/s is 1050 mW, and at 1.4 Gs/s is 1290 mW, with a power supply of −3.3 V. [ABSTRACT FROM AUTHOR]

Many modern statistical analysis research efforts are focused on solving the limited computational resources problem that arises when dealing with large datasets. One popular and effective method to address this challenge is to obtain informative subdata from the full dataset based on optimal subsampling probabilities. In this article, we present an optimal subsampling approach for big data modal regression from the perspective of minimizing asymptotic mean squared error. The estimation procedure is achieved by running a two-step algorithm based on the modal expectation-maximization algorithm when the bandwidth for the modal regression is not related to the subsample size. Under certain regularity conditions, we investigate the consistency and asymptotic normality of the subsample-based estimator given the full data. Furthermore, an optimal bandwidth selection approach within this framework is also investigated. Simulation studies demonstrate that our proposed subsampling method performs well in the context of big data modal regression. Empirical evaluation is also conducted using real data. [ABSTRACT FROM AUTHOR]

Data aggregation using the shortest path is a challenging issue in wireless sensor networks. Data aggregation slows the communication process and consumes many resources available to sensor nodes. So, while transmitting the aggregated data, it is crucial to identify the shortest and most reliable route for energy-efficient data aggregation from the source to the sink node. However, the nodes closer to the sink node are heavily utilized in multi-hop transmission and succumb to early death, which causes energy imbalance and an energy hole problem in the network. To overcome this problem, we propose an innovative node utilization index-based data routing and aggregation (NUIDRA) protocol. The NUIDRA protocol is designed and implemented in two phases. The first phase is to determine the shortest path from the source node to the sink node based on the amount of bandwidth utilized by each sensor node, minimum hop count, node's residual energy, and data aggregation factor. In the second phase, the selected shortest path is used for data transmission and aggregation using the dynamic selection of the aggregator node. The choice of aggregator node is based on the node's utilization index (UI) and adjacent node count from which it receives the data. The NUIDRA protocol is compared and analysed with I-LEACH and QADA protocols. The extensive simulation results show that in the proposed NUIDRA protocol, there is an increase in the average throughput of 70%, packet delivery ratio by 41.93%, and the average latency is reduced by 58.15% as compared to the I-LEACH protocol. Further, there is an increase in the average throughput of 24%, packet delivery ratio by 7.31%, and the average latency is reduced by 53.23% as compared to the QADA protocol for a data packet size of 512 bytes. [ABSTRACT FROM AUTHOR]

In this paper, a stabilized and wavelength-selective erbium-doped fiber (EDF) laser architecture with single-longitudinal-mode, high optical signal to noise ratio (OSNR), stability, wide tunability and narrower linewidth is investigated experimentally. To suppress the dense longitudinal-mode fluctuations and reduce the output linewidth, the proposed four-fiber-ring with Rayleigh backscattering feedback injection and an EDF based saturable absorber is added in the ring cavity. So, the presented EDF laser configuration can provide a 68 nm wide wavelength-selective bandwidth of 1513.0–1581.0 nm by operating the original C-band gain-medium and also achieve a flattened power output with 0.3 dB power fluctuation in the bandwidth of 1529.0–1573.0 nm. Moreover, the related output characteristics of the proposed fiber laser are executed and discussed. [ABSTRACT FROM AUTHOR]

This study investigates the system-level performance of variable recruitment (VR) fluidic artificial muscle (FAM) actuator bundles using a model that incorporates FAM interaction effects. A VR bundle combines multiple FAMs to act as one actuator in which the FAMs are sequentially recruited to increase overall efficiency. In a VR bundle, inactive/low-pressure FAMs are compressed beyond their free strains, exerting resistive forces opposing that of active FAMs. A recent model that captures this behavior is used to simulate sinusoidal contraction of a VR bundle with a hanging mass load. The implications of inter-FAM effects on the force-strain space of a VR bundle are discussed and a method of recruitment state transition required to track a sinusoid is proposed. The dynamics of the electrohydraulic subsystems are presented and used to evaluate its system efficiency and bandwidth limits. Three different electrohydraulic configurations are considered: (1) continuous motor operation with constant pump displacement, (2) intermittent motor operation with constant pump displacement, and (3) continuous motor operation with variable pump displacement. Simulation results show the superior bandwidth capabilities of VR bundles by demonstrating its ability to track sinusoids with amplitudes up to 16% strain at frequencies greater than 0.5 Hz, compared to that of a single equivalent cross section area motor unit (SEMU). In addition to increased bandwidth limit, system efficiencies averaged over a range of amplitudes show up to 170% increase when comparing a VR bundle using variable pump displacement to a SEMU using constant pump displacement. [ABSTRACT FROM AUTHOR]

This paper follows a detection-theoretic approach for using synthetic-aperture measurements, made at multiple moving passive receivers, in order to form an image showing the locations of stationary sources that are radiating unknown electromagnetic or acoustic waves. The paper starts with a physics-based model for the propagating fields, and, following the general approach of McWhorter et al (2023 arXiv:2302.06816, IEEE Open J. Signal Process. 4 437–51), derives a detection statistic that is used for the image formation. This detection statistic is a quadratic function of the data. Each point in the scene is tested as a possible hypothesized location for a source, and the detection statistic is plotted as a function of location. Because this image formation process is nonlinear, the standard linear methods for determining resolution cannot be applied. This paper shows how to analyze the detection image by first writing the noiseless image as a coherent sum of shifted complex ambiguity functions of the source waveform. The paper then develops a technique for calculating image resolution; resolution is found to depend on the sensor-source geometry and also on the properties (bandwidth and temporal duration) of the source waveform. Optimal filtering of the image is given, but a simple example suggests that optimal filtering may have little effect. Analysis is also given for the case in which multiple sources are present. [ABSTRACT FROM AUTHOR]

The classical synthetic aperture radar (SAR) imaging techniques based on matched filters are limited by data bandwidth, resulting in limited imaging performance with side lobes and speckles present. To address the high-resolution SAR imaging problem, sparse reconstruction has been extensively investigated. However, the state-of-the-art sparse recovery methods seldom consider the complex-valued reflectivity of the scene and only recover an approximated real-valued scene instead. Furthermore, iterative schemes associated with the sparse recovery methods demand a high computational cost, which limits the practical applications of these methods. In this paper, we establish a sphere-constrained magnitude-sparsity SAR imaging model, aiming at enhancing the SAR imaging quality with high efficiency. We propose a non-convex non-smooth optimization method, which can be accelerated by stochastic average gradient acceleration to be scalable with large-scale problems. Numerical experiments are conducted with point-target and extended-target simulations. On the one hand, the point-target simulation showcases the superiority of our proposed method over the classical methods in terms of resolution. On the other hand, the extended-target simulation with random phases is considered to be in line with the practical scenario, and the results demonstrate that our method outperforms the classical SAR imaging methods and sparse recovery without phase prior in terms of PSNR. Meanwhile, owing to the stochastic acceleration, our method is faster than the existing sparse recovery methods by orders of magnitude. [ABSTRACT FROM AUTHOR]

A queueing system with the discipline of flexible limited sharing of the server is considered. This discipline assumes the admission, for a simultaneous service, of only a finite number of orders, as well as the use of a reduced service rate when the bandwidth required by the admitted orders is less than the total bandwidth of the server. The orders arrive following a batch-marked Markov arrival process, which is a generalization of the well-known MAP (Markov arrival process) to the cases of heterogeneous orders and batch arrivals. The orders of different types have different preemptive priorities. The possibility of an increase or a decrease in order priority during the service is suggested to be an effective mechanism to prevent long processing orders from being pushed out of service by justarrived higher-priority orders. Under a fixed priority scheme and a mechanism of dynamic change of the priorities, the stationary analysis of this queueing system is implemented by considering a suitable multidimensional continuous-time Markov chain with a generator that has an upper Hessenberg structure. The possibility of the optimal restriction on the number of simultaneously serviced orders is numerically demonstrated. [ABSTRACT FROM AUTHOR]

Summary: In postdisaster rescue scenario, unmanned aerial vehicles (UAVs) are effective tools to help ground users in disaster areas to transmit rescue‐critical data to the relief center in time due to their flexible mobilities and fast deployment. However, how UAVs choose disaster areas to take part in traffic offloading with limited bandwidth resources is challenging. This article investigates UAVs' access selection and disaster areas' bandwidth allocation scheme by jointly optimizing network throughput, bandwidth and UAVs' energy cost. The UAVs form coalitions to participate in traffic offloading cooperatively, where each UAV selects a disaster area independently. Specifically, the bandwidth resources are dynamically allocated to all disaster areas when a new coalition partition forms. The UAVs adjust their access choices for disaster areas when the bandwidth allocation changes. When no UAVs migrate to other disaster areas, the network achieves a stable state. The UAVs fly to the final selected disaster area and provide traffic offloading services. To resolve traffic offloading competitions yet enable cooperations among UAVs, we address the UAVs' access selection issue by coalition formation game. A gradient projection method is then proposed to allocate bandwidth resources which maximizes the benefit of the network. We demonstrate that the UAVs' access selection and disaster areas' bandwidth allocation algorithms are convergent. The simulation results demonstrate that our proposed cooperation order is better than the pareto and selfish orders, thereby increasing the benefit of the network. [ABSTRACT FROM AUTHOR]

Based on a mathematical model and empirical test, this paper explores the incentive of income for aspirations and its channels, forging links between theory and data. Results present evidence that income significantly inspires one's aspirations, and all conclusions still hold after overcoming the interference of potential endogenous issues. In terms of channels, the "aspirations window" (a set of similar perceivable individuals) and "bandwidth load" (the mental space to think, process problems, and come up with solutions) play the mediating role in the stimulation of money; that is, low incomes will make aspirations window narrower and bandwidth load heavier, which is a momentous force behind one's aspirations failure. This paper also enlightens income distribution and the construction of internal motivation mechanisms. [ABSTRACT FROM AUTHOR]

A new tri-band rectangular DRA is simulated and tested for wireless communication applications like ISM, Wi-Max, and WLAN. The dielectric resonator antenna structure is excited by a 50Ω transmission line. The rectangular DRA with concentric square rings is designed to acquire the operation of triple-bands. The investigated antenna parametric study has been accomplished on HFSS tool. The implemented design exhibits triple-band characteristics at 2.16-2.57 GHz, 3.35-4.45 GHz, and 5.35-5.95 GHz, with a fractional bandwidth of 17.3%, 28.1%, and 10.6%, respectively. The implemented concentric square rings are imposed on FR4-substrate material to emphasize the antenna parameters and to minimize the size. The designed antenna has a compact size, good radiation properties, and optimal operational bandwidth. To validate the antenna, it is fabricated, and the results match well with the simulated ones. The antenna is well suitable for wireless communication applications. The fabricated rectangular DRA is measured by using MS2037C Anritsu-Combinational Analyzer. [ABSTRACT FROM AUTHOR]

In order to realize the real-time processing and analysis of astronomical ultrawide bandwidth signals, this study proposes a sub-band division algorithm based on RFSoC. The algorithm uses Kaiser window to design FIR prototype low-pass filter, adopts critical sampling polyphase filter bank to decompose ultra-wide bandwidth signal into several sub-bands, and encapsulates each sub-band into VDIF data frame and sends it to GPU server. The algorithm is implemented on RFSoC platform, and its effectiveness is verified by simulation and actual observation. The experimental results show that the algorithm can divide the astronomical ultra-wide bandwidth signal into multiple sub-bands in real time, packetize and transmit them to GPU. This research provides reproducible design and project for ultra-wide bandwidth signal sub-band division with low spectrum leakage and aliasing, high data accuracy, and fast processing speed. [ABSTRACT FROM AUTHOR]

A general strategy for designing bi‐layer reflection‐transmission integrated dual‐mode metasurfaces is presented with flexible bandwidth control. The design of such metasurfaces is enlightened by introducing a cutting hole in the ground plane, which not only acts as a filter for reflection and transmission but also has an eloquent role for bandwidth control. For proof of concept, a bi‐layer metasurface consisting of split ring resonators (SRRs) is designed on the top side and I‐shaped resonators on both sides. The proper adjustment of ground cut/hole shifts the two co‐polarized resonances (initial resonances of the SRRs) close to each other, and in addition, converts wideband cross‐polarized reflection (in between the two initial co‐polarized resonances of SRR) to co‐polarized reflection. This results in a broadband response by shifting two co‐polarized resonances close to each other and converting cross‐polarized reflection into co‐polarized reflection. It is demonstrated that a simple SRR can be responsible for broadband (7.9–12 GHz) reflection while an I‐shaped structure is used for transmission with central frequency at 17.58 GHz with independent phase controls. To endorse the proposed strategy, a metasurface prototype is fabricated and tested for the generation of vortex beams and focusing. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) interferometry (InSAR) is a well-established remote sensing technique capable of providing accurate topographic information of an area. Multiple scattering occurring at different heights within a single resolution cell, however, cannot be resolved using a single baseline and results in a degradation of the height accuracy. Techniques such as polarimetric InSAR and SAR tomography tackle this problem using additional measurements to obtain the three-dimensional structure of the volume. However, polarimetry-based methods assume orthogonal and deterministic scattering mechanisms and tomography requires numerous observations. This paper presents a novel approach to retrieving the three-dimensional structure of semitransparent media using wide fractional bandwidth InSAR. The frequency dependency of the InSAR coherence is exploited to retrieve the three-dimensional structure, assuming that signals with wide fractional bandwidth are available, as is the case for unmanned aerial vehicles (UAVs) or drones. As the extinction is, in general, frequency-dependent, a third observation may improve the inversion results. Simulations of different scenarios show that the frequency profile can be inverted to obtain information about the three-dimensional scattering structure. The acquired data also enable retrieval of the phase center depth as a function of frequency. This method allows for frequent and accurate monitoring of semitransparent targets, e.g., forests and vegetation, using a swarm of two or three drones. [ABSTRACT FROM AUTHOR]

Microwave hyperspectral instruments represent one of the main atmospheric sounders of China's next-generation Fengyun meteorological satellites. In order to better apply microwave hyperspectral observations in the fields of atmospheric parameter retrieval and data assimilation, this paper analyzes the sensitivity of trace gases to five selected bandwidth channels using a radiative transfer model based on the simulated data of microwave hyperspectral radiances at 50–60 GHz. This method uses information entropy and a weighting function to select channels and analyze the impact of this on the retrieval accuracy of atmospheric profiles before and after channel selection. The experimental results show that channel selection can reduce the number of channels by approximately 74.05% while maintaining a large amount of information content, and this retrieval effect is significantly better than that of MWTS-III. After channel selection, the 10 MHz, 30 MHz, and 50 MHz bandwidths have the best retrieval results in the stratosphere, whole atmosphere, and troposphere, respectively. When considering the number of channels, computational scale, and retrieval results comprehensively, the channel selection method is effective. [ABSTRACT FROM AUTHOR]

In this article, we present new design techniques to improve the gain and impedance bandwidth of short backfire antennas. For the gain enhancement procedure, our approach was to flare the rim of the antenna, which simultaneously led to an increase in the impedance bandwidth of the antenna. Parametric studies were carried out to obtain the optimal flaring angle. The peak realized gain was obtained as 17.2 dBi with an impedance bandwidth of 55% (2.4 dB and 28.6% increase in gain and bandwidth, respectively, compared to the unflared antenna). To further enhance the impedance bandwidth, an inductive iris was added to improve impedance matching at the waveguide aperture. We varied the width of the iris to obtain the optimal width that provided the best gain and impedance bandwidth result of 17.1 dBi and 66% (~40% increase compared to the unflared antenna without iris). To experimentally verify the work, prototypes were fabricated and tested. We found good agreement between simulation and measurement. The results of this study indicate that gain and bandwidth can be enhanced through optimized geometrical modification of the SBF structure. Furthermore, our 3D-printed technique demonstrates a mass reduction compared with conventional metallic structures. [ABSTRACT FROM AUTHOR]

Metalenses have provided a good solution to the bulkiness of conventional refractive lenses. Due to the subwavelength feature sizes of the metalens structure, the increasing fabrication difficulties at high frequencies limit its application in the terahertz and optical regime. Moreover, the deeply subwavelength features of the metasurface unit cells usually make the cells strongly resonant, which limits the bandwidth of the metalens. In this paper the usage of aggressive discretization in a metalens design is investigated, and it is found that aggressive discretization can lead to the usage of weakly resonant and relatively large unit cells, which leads to excellent broadband performance and dramatically relaxes the feature size tolerance of the metalens. For examples, two terahertz focusing metalenses are designed which feature large numerical apertures (NA = 0.86), diffraction‐limited focusing over a broad bandwidth (240–400 GHz, or 50% bandwidth), and minimum feature sizes of 0.1 mm. These tolerance‐relaxed terahertz metalenses are successfully constructed using conventional printed‐circuit‐board fabrication technology. The experimental measurements validate the simulated performances. Compared to existing terahertz meta‐devices based on micro‐fabrication or nano‐fabrication technologies, this paper opens door to a kind of high‐quality terahertz metasurfaces featuring low‐cost, rapid, and established fabrication. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of robust output feedback control tracking for a class of nonlinear dual-rate sample-data systems subject to time-varying disturbances. These dual-rate systems, known as slow measurement fast control (SMFC) systems, are characterised by a slow sampling rate of the sensor and a fast updating rate of the controller. To facilitate high-frequency signal tracking, this paper introduces an alternating predictive generalised proportional integral observer (APGPIO). The proposed control method not only effectively restores the system state and captures disturbance changes between samples but also enhances the control bandwidth and anti-disturbance ability, enabling effective tracking of high-frequency reference outputs. By combining it with a fast updating sample-data feedback controller, APGPIO utilises predictive methods to increase the sampling rate of the system's sensors, matching the update frequency of the controller. Stability analysis demonstrates that the tracking error of this hybrid nonlinear system converges to a bounded region centred at the origin. Finally, the designed method's high control bandwidth and anti-disturbance ability are demonstrated through multiple sets of simulations using a real system. [ABSTRACT FROM AUTHOR]

This study focuses on the performance of CICE and its Elastic-Viscous-Plastic (EVP) dynamical solver. The study has been conducted in two steps. First, the standard EVP solver has been extracted from CICE for experiments with refactored versions of it. Secondly, one refactored version was integrated and tested as part of the full model. Two dominant bottlenecks were revealed. The first is the number of MPI and OpenMP synchronization points required for halo exchanges during each time-step combined with the irregular domain of active sea ice points. The second is the lack of Single Instruction Multiple Data (SIMD) code generation. The study refactors the standard EVP solver based on two generic patterns. The first pattern exposes how general finite-differences on masked multi-dimensional arrays can be expressed in order to produce significantly better code generation. The primary change is that the memory access pattern is changed from random access to direct access. The second pattern exposes an alternative approach to handle static grid properties. The measured single core improvement is increased by more than a factor of five compared to the standard implementation. The refactored implementation strong scales on the Intel® Xeon® Scalable Processor Series node until the available bandwidth of the node is used. For the Intel® Xeon® CPU Max Series Series there is sufficient bandwidth to allow the strong scaling to continue for all the cores on the node resulting in a single node improvement factor of 35 over the standard implementation. This study also show improved performance on GPU processors. [ABSTRACT FROM AUTHOR]

Starting a virtual machine (VM) is a common operation in cloud computing platforms. In order to achieve better management of resource provisioning, a cloud platform needs to accurately estimate the VM boot time. In this paper, we have conducted several experiments to analyze the factors that could affect VM boot time in a computer cluster with shared storage. We also implemented four models for VM boot time prediction and evaluated the performance of the four models based on the datasets of four hosts and seven hosts in our environment, where the four models are the rule-based model, the regression tree model, the random forest regression model, and the linear regression model. According to our analysis, we found that host capability and maximal network bandwidth are two main factors that can influence VM boot time. We also found that VM boot time becomes harder to predict when booting VMs at different hosts concurrently due to competition between hosts to obtain resources. According to the experimental results, the proposed random forest regression is the best model for VM boot time prediction with an average accuracy of 94.76 % and 96.59 % in predicting VM boot time in two clusters with four and seven compute hosts, respectively. [ABSTRACT FROM AUTHOR]

A hardware and software complex for estimating the dispersion distortion bandwidth and fading coherence bandwidth in a satellite (transionospheric) radio channel based on the results of GPS-monitoring of the ionosphere are theoretical substantiated and developed. The basis for solving this problem is development of a structural–physical model of the radio channel, which makes it possible to simultaneously take into account the phase dispersion of the wave and diffraction on small-scale inhomogeneities of the ionosphere. Analytical dependences of the dispersion distortion bandwidth and coherence of frequency-selective fading on the mean value and small-scale fluctuations of the total electron content of the ionosphere are obtained. It is shown that under conditions of ionospheric disturbances, the fading coherence bandwidth can be much smaller than the dispersion band. In accordance with the obtained dependences, a structure is developed for building a hardware and software complex for estimating the dispersion and coherence bandwidths of a satellite radio channel based on improvement of the method for GPS monitoring of the total electron content of the ionosphere with small-scale inhomogeneities. [ABSTRACT FROM AUTHOR]

The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis, YFP) possesses the ability to detect distance through echolocation signals, and its sonar signal signature is adjusted to detect different targets. In order to understand the vocal characteristics of YFPs in different behavioral states and their differential performance, we recorded the vocal activities of YFPs in captivity during free-swimming, feeding, and nighttime resting and quantified their signal characteristic parameters for statistical analysis and comparison. The results showed that the number of vocalizations of the YFPs in the daytime free-swimming state was lower than that in the feeding and nighttime resting states, and the echolocation signals emitted in these three states showed significant differences in the −10 dB duration, −3 dB bandwidth, −10 dB bandwidth, and root-mean-square (RMS) bandwidth. Analysis of the resolution of the echolocation signals of the YFPs using the ambiguity function indicated that their distance resolution could reach the millimeter level. These results indicate that the echolocation signal characteristics of YFPs present diurnal differences and that they can be adjusted with changes in their detection targets. The results of this study can provide certain scientific references and foundations for the studies of tooth whale behavioral acoustics, and provide relevant scientific guidance for the conservation and management of YFPs. [ABSTRACT FROM AUTHOR]

We investigate whether varying wavefield contributions are the likely cause to variation in microtremor horizontal-to-vertical spectral ratio (MHVSR) amplification shape between six sites in the relatively homogeneous geologic setting of Windsor, Ontario. We quantify the MHVSR shape in terms of peak broadness and its fitness using mathematical functions to identify potential wave type contributions. We develop a technique that uses particle motion plots of cross-correlated microtremor recordings to establish the dominant wave types contributing to the microtremor wavefield within three important frequency bandwidths (below, spanning, and above the fundamental peak frequency). We investigate the variability in the inverted shear-wave velocity (VS) depth profile by performing 21 MHVSR inversions with varying Rayleigh, Love, and body wave contributions. The impact to seismic site characterization is that the depth and VS of the resonator (half-space) layer are overestimated consistently by an average of 28% compared to the often-default-assumed Rayleigh ellipticity forward amplification model. Our study demonstrates the importance of correctly identifying wave type contributions of the microtremor wavefield for the proper estimation of VS depth profiles, especially to obtain correct thickness of the sediment layer and resonator VS and thereby the average VS of the upper 30 m (VS30). [ABSTRACT FROM AUTHOR]

This article presents a resistive‐reactive Class‐X power amplifier (PA) with bandwidth beyond one octave. By introducing resistive component into the second‐harmonic load of Class‐X power amplifier, the impedance design space is expanded. The basic theory of extended Class‐X PA is deduced, including impedance calculation, high‐efficiency design consideration and targeted impedance trace design. An impedance overlapping region between fundamental and second‐harmonic impedances with high drain efficiency is obtained, paving the way for bandwidth enhancement. For validation, the Class‐X and extended Class‐X theory are employed to design a broadband PA with bandwidth of 0.6–2.6 GHz (125%), drain efficiency of 57%–70%, and gain of 10.2–13.2 dB. [ABSTRACT FROM AUTHOR]

The article details the development and production of an ultra‐wideband discrete single‐pole‐double‐throw (SPDT) Switch, measuring 28.3×14 mm2 $28.3\times 14\unicode{x0200A}\,\text{mm}{}^{2}$, and functioning within the 23.4–31 GHz frequency range, encompassing 24 and 28 GHz. This switch is specifically engineered to bolster high‐frequency systems in automotive and fifth‐generation applications. Our findings demonstrate that the discrete SPDT switch performs on par with integrated circuits while delivering consistent performance throughout its frequency spectrum. Furthermore, it offers a cost‐effective fabrication process. The switch exhibits an insertion loss ranging from 1.6 to 2.2 dB, with return loss and isolation surpassing 15 and 25 dB, respectively, across the majority of the frequency bandwidths. [ABSTRACT FROM AUTHOR]

In the letter, a wideband filtering power divider (FPD) with ultra‐large coupling coefficient using air‐dielectric broadside‐coupled lines is proposed. The broadside‐coupled line and single transmission line are alternately connected to construct three resonators, which can be used for large bandwidth and high selectivity filtering. An improved substrate‐integrated suspended line (SISL) structure with two inner layers is developed. In the structure, the broadside coupling occurs by the air. The overall structure is implemented based on the low‐cost FR4 dielectric material. The designed FPD is simulated and fabricated. The results demonstrate its excellent performance, with center frequency of 6 GHz, a fractional bandwidth (FBW) of 80.8%, a maximum coupling coefficient of 0.84, an insertion loss of less than 0.29 dB, and an out‐of‐band rejection of more than 52 dB. [ABSTRACT FROM AUTHOR]

A novel aperture‐shared dual‐wideband 5G antenna with dual polarization in the sub‐6 GHz band and multi‐input multi‐output (MIMO) function in the 28‐GHz band is presented in this work. A dual‐polarized megnetoelectric dipole (ME‐dipole) with wide bandwidth is introduced in the sub‐6 GHz band. Based on the partial structure reuse method, four 2 × 2 substrate integrated waveguide (SIW) cavity‐backed patch arrays are integrated into the electric dipole structure of the ME‐dipole to construct a 28‐GHz 2 × 2 MIMO system. Two high‐order SIW cavity modes that cooperate with patch modes are used to enhance bandwidth in the 28‐GHz band. For demonstration, a prototype of the proposed antenna was fabricated and measured. The simulated results are in good agreement with the measured results, showing wide bandwidths of 39.6% and 10.85% in the sub‐6 GHz and the 28‐GHz bands, respectively. In addition, excellent measured in‐band and cross‐band isolations of over 44.4 dB and 45.2 dB are obtained, respectively. [ABSTRACT FROM AUTHOR]

The authors presents a low‐profile wideband circularly polarised (CP) millimetre‐wave (mmWave) elliptical integrated lens antenna (ILA) fabricated by dielectric 3D printing technology. The proposed lens is integrated with a dielectric polariser and an air cavity for phase compensation, which can transfer incident waves from linearly polarised (LP) to planar CP waves over a wide bandwidth. Compared to the classic bifocal ILA, the proposed lens has a low profile. The phase compensation is performed by introducing a specifically shaped air cavity, which greatly reduces the length and weight of the lens. The polariser causes the two electric field components Ex and Ey to degenerate with an orthogonal phase difference, which results in the wideband characteristics of the antenna. The polariser, air cavity and lens can be conveniently and precisely fabricated by low‐cost 3D printing technology. Measurements show that the proposed ILA has a wide axial ratio (AR) bandwidth of 21.9–32.6 GHz, while the gain reaches 22.54 dBic with a 38% size reduction and a 60.7% weight reduction. Benefiting from the low profile, high gain, wide bandwidth and low cost, the proposed ILA has great potential to be the candidate antenna for 5G applications and satellite communications. [ABSTRACT FROM AUTHOR]

A new multi‐band frequency response controlling method using groove loading technique on the narrow wall of an open‐ended waveguide is proposed by the authors. The feature of this scheme is a larger stopband spacing that is independent of the position of the loading structure. A tri‐band antenna is designed as an example to verify the effectiveness of the idea. Two notches are introduced, and the bandwidths, as well as stopband spacings, can be adjusted by independent parameters. The tri‐band prototype can be fabricated using 3D printing technology or machining technology. Reasonable agreement between the measured and simulated results of impedance and radiation characteristics have been achieved. [ABSTRACT FROM AUTHOR]

Hotspot detection from geo‐referenced urban data is critical for smart city research, such as traffic management and policy making. However, the classical clustering or classification approach for hotspot detection mainly aims at identifying "hotspot areas" rather than specific points, and the setting of global parameters such as search bandwidth can lead to inaccurate results when processing multi‐density urban data. In this article, a data‐driven adaptive hotspot detection (AHD) approach based on kernel density analysis is proposed and applied to various spatial objects. The adaptive search bandwidth is automatically calculated depending on the local density. Window detection is used to extract the specific hotspots in AHD, thus realizing a small‐scale characterization of urban hotspots. Through the trajectory data of Harbin City taxis and New York City crime data, Geo‐information Tupu is used to analyze the obtained specific hotspots and verify the effectiveness of AHD, providing new ideas for further research. [ABSTRACT FROM AUTHOR]

The ability to manipulate the refractive index is a fundamental principle underlying numerous photonic devices. Various techniques exist to modify the refractive index across diverse materials, making performance comparison far from straightforward. In evaluating these methods, power consumption emerges as a key performance characteristic, alongside bandwidth and footprint. Here a comprehensive comparison of the energy and power requirements for the most well‐known index change schemes is undertaken. The findings reveal that while the energy per volume for index change remains within one or two orders of magnitude across different techniques and materials, the power consumption required to achieve switching, 100% modulation, or 100% frequency conversion can differ significantly, spanning many orders of magnitude. As it turns out, the material used has less influence on power reduction than the specific resonant or traveling wave scheme employed to enhance the interaction time between light and matter. Though this work is not intended to serve as a design guide, it does establish the limitations and trade‐offs involved in index modulation, thus providing valuable insights for photonics practitioners. [ABSTRACT FROM AUTHOR]