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A novel high-temperature resistant calcium aluminate cement-based electromagnetic wave absorption composites were prepared using carbon fibers, Al 2 O 3 hollow spheres, and expanded polystyrene spheres (EPS). EPS, as a pore forming agent, was oxidized as to form pores at high temperatures. The effects of carbon fibers doping levels and various high-temperature treatment on the permittivity of the composites from 0.3 to 18 GHz were investigated in detail. Additionally, a high-temperature resistant porous cone cement-based electromagnetic wave absorption structure was designed, and its microwave absorption mechanism was explored. The findings indicated that the permittivity of electromagnetic wave absorption composites exhibited stability even after undergoing high-temperature treatments below 350 °C, while experiencing a decrease at 500 °C. Following cyclic treatments at temperatures of 200 °C and 350 °C, the cone calcium aluminate porous cement-based composites still exhibited outstanding electromagnetic wave absorption performance, achieving reflection loss (RL) bandwidths below −30 dB of 17.4 GHz and 17.2 GHz, respectively, within the frequency range of 0.3–18 GHz. Furthermore, the RL of the composite from 4 to 18 GHz after 500 °C treatment remained less than −50 dB. Thus, present work associated with the materials and structural design of calcium aluminate porous cone cement-based composites provided a potential insight into the high-temperature electromagnetic wave absorption engineering applications. [Display omitted] • Cone cement-based wave-absorbing composites exhibit excellent broadband absorbing properties. • The cone composites maintain stable electromagnetic properties after cyclic treatment at a temperature of 350 °C. • The cone exhibits a RL below −50 dB in 4–18 GHz after treatment at 500 °C. [ABSTRACT FROM AUTHOR]

In this paper, an ultra-wideband substrate integrated coaxial line (SICL) array based on silicon-based MEMS process is proposed for high-speed data transmission. A quasi-coaxial transition array is designed to connect the SICL array with grounded-coplanar waveguides (GCPWs). Moreover, a stepped-impedance matching structure is introduced to reduce the discontinuities and improve the transmission performance. For high efficiency design, a Bayesian Optimization (BO)-based approach is adopted to optimize dimensions of the proposed SICL array. The objective function is set to be the weighted combination of the bandwidth and the crosstalk of the proposed array structure to obtain wide bandwidth and low crosstalk simultaneously. With the proposed BO-based approach, iteration times can be reduced by approximately 99.9% compared with the parametric sweep method. A 40-channel SICL array is designed and fabricated under silicon-based Micro-electromechanical Systems (MEMS) process. Ultra-wideband of 110GHz is measured in each channel with the insertion loss less than 3dB and the return loss larger than 15dB. The couplings between two adjacent channels are no more than −30dB. Good eye diagram and low bit error rate (BER) are achieved for each channel at data rate of 95Gb/s and hence the total data rate can reach 3.8Tb/s. The bandwidth density of the proposed SICL array is 0.164Gb/s/μm, which is much higher than those of the conventional SICLs. [ABSTRACT FROM AUTHOR]

For ultra-high-speed digital transmission, required by 5G/6G communications, ultra-wideband common-mode rejection (CMR) structures with autonomous phase-balancing capability are proposed. Common-mode noise, caused by phase and amplitude unbalances, is one of the most undesired disturbances affecting modern digital circuits. According to the circuit design guides with a typically used differential line (DL) for high-speed digital transmission, common-mode rejection is achieved using CMR filters, and the unbalanced phase, caused by a length difference between the two signal lines of a DL, is compensated by inserting an additional delay line. However, due to nonlinear phase interactions between the two DLs and unbalanced electromagnetic (EM) interferences, the conventional compensation method is frequency-limited at around 10 GHz. To significantly enhance the common-mode rejection level and extend the phase recovery bandwidth, the proposed CMR structure utilizes a planar balanced line (BL), such as a coplanar stripline (CPS) or a parallel stripline (PSL), along with additional conductor strips arranged laterally near the BL. To demonstrate the performance of the proposed BL-based CMR structures, various types of CMR structures are fabricated, and the measurement results are compared with the 3D EM simulation results. As a result, it is proven that the proposed BL-based CMR structures have the capability to reject the common-mode noise with suppression levels of more than 10 dB and to simultaneously recover the phase balance from near DC to over 40 GHz. [ABSTRACT FROM AUTHOR]

To overcome the mismatch issues and achieve high data rate for medical applications in human body environment, an ultra-wideband implantable MIMO antenna is proposed. The antenna has a compact size of 9 × 9 × 0.508 mm3. By loading an H-shaped parasitic patch on top of the superstrate to improve impedance matching, the antenna achieves an ultra-wide bandwidth of 1.24 GHz, covering two frequency bands: industrial, scientific, and medical (ISM) (2.4-2.48 GHz), and midfield band (1.52-1.693 GHz). The MIMO antenna consists of two elements and shares a slotted ground plane, achieving high isolation. The |S21| is below −20 dB in both simulation and measurement within the ultra-wide operating frequency band. The antenna is integrated with virtual electronic components, and the robustness of the antenna is evaluated by comparing and analyzing the performance before and after integration. S-parameters are measured, more than 62.6% of the bandwidth was obtained. [ABSTRACT FROM AUTHOR]

A compact, low loss microstrip ultra-wideband (UWB) bandpass filter (BPF) with a narrow notch band is proposed in this article for using wireless communication applications within the unlicensed UWB range reported by the Federal Communications Commission. A systematic approach is presented to establish the UWB-BPF structure followed by a narrow notch within it. The UWB-BPF response is achieved by integrating a defected structures-based lowpass filter and a short-stepped impedance stub-based highpass filter. The narrow notch band is obtained by embedding two-stepped impedance stubs. The physical dimensions of the stubs can be optimized to select a specific frequency for the notch band. The UWB-BPF structure without the notched band, having a center frequency of 3.69 GHz, provides a fractional bandwidth (FBW) of 157%. The stopband suppression is −26 dB and it is broadened up to 15 GHz. On the other hand, the notched band response is obtained at 5.8 GHz with an FBW of 49.78% which is used for avoiding interference from the wireless local area network. The proposed structures are fabricated and measured for experimental validation. [ABSTRACT FROM AUTHOR]

This paper comprehensively analyses the specific absorption rate (SAR) for an ultra-wideband (UWB) wearable antenna designed for body-centric communication applications. The study is motivated by the extent of electromagnetic radiation in our surroundings, raising worries about health for wireless device users and wearable devices that utilize UWB technology. The proposed antenna is made of a foam substrate having a dielectric constant of 1.07, a thickness of 2 mm with a dimension of 36 × 48 × 2 mm 3 . The designed structure optimizes UWB (3.1–10.6 GHz) in connotation with the ISM band of 2.4 GHz. The proposed antenna works well over the wide frequency range resulting in a bandwidth of 11.53 GHz and a total gain of 8.05 dBi. An excellent impedance matching is obtained by creating a stub at the feed point which gives the maximum value of S11 as − 44.88 dB. The analysis focuses on the SAR values to measure the rate of electromagnetic energy absorption by human tissues over 1 and 10 g by constructing an equivalent three-layer body phantom model. The results indicate that the proposed antenna exhibits SAR values well within the limits set by international standards of 1.6 W/kg averaged over 1 g of tissue and 2 W/kg for 10 g of tissue, while maintaining efficient radiation characteristics across the UWB spectrum. [ABSTRACT FROM AUTHOR]

This article presents a numerical analysis of a very thin concentric octagonal elliptical ring resonator (CORR) with a cylindrical rod optical nano-metamaterial absorber (ONMMA) that is designed to absorb solar energy in the infrared, visible, and ultraviolet ranges. The ONMMA is made of gold and nickel resonators on a quartz substrate with a gold plate ground material. The absorption rate of the ONMMA is over 90% from 593.84–829.28 THz, with an average absorption rate of 93.891%. This means that the ONMMA can absorb more than 80% of the energy in the infrared, visible, and a small portion of the ultraviolet range. It also has an absorption rate of over 75% from 226.64–853.04 THz, with an average absorption rate of 88.945%. This covers the entire visible spectrum, with a small portion in the infrared and ultraviolet regions. The design has an operational bandwidth of 200–920 THz, with an average absorption rate of 86.424%. The ONMMA achieves a maximum absorption rate of 99.866% at 705.44 THz. The design of the octagonal ONMMA ensures that it is not affected by the polarization of the incident light and can absorb energy even at oblique angles up to 60 degrees. The study also analyzed the effects of different materials and geometrical parameters on the absorption characteristics, as well as the distribution of surface current, magnetic field, electric field, and power loss. The proposed ONMMA has promising applications in infrared detection, solar cells, and multicolor imaging applications. [ABSTRACT FROM AUTHOR]

Ultra-wideband (UWB) time-difference-of-arrival (TDOA)-based localization has emerged as a promising, low-cost, and scalable indoor localization solution, which is especially suited for multi-robot applications. However, there is a lack of public datasets to study and benchmark UWB TDOA positioning technology in cluttered indoor environments. We fill in this gap by presenting a comprehensive dataset using Decawave's DWM1000 UWB modules. To characterize the UWB TDOA measurement performance under various line-of-sight (LOS) and non-line-of-sight (NLOS) conditions, we collected signal-to-noise ratio (SNR), power difference values, and raw UWB TDOA measurements during the identification experiments. We also conducted a cumulative total of around 150 min of real-world flight experiments on a customized quadrotor platform to benchmark the UWB TDOA localization performance for mobile robots. The quadrotor was commanded to fly with an average speed of 0.45 m/s in both obstacle-free and cluttered environments using four different UWB anchor constellations. Raw sensor data including UWB TDOA, inertial measurement unit (IMU), optical flow, time-of-flight (ToF) laser altitude, and millimeter-accurate ground truth robot poses were collected during the flights. The dataset and development kit are available at https://utiasdsl.github.io/util-uwb-dataset/. [ABSTRACT FROM AUTHOR]

This study proposes an ultra‐wideband multilayer absorber by combining frequency selective surface (FSS) and absorbing material. The structure is composed by three layers which are FSS loaded with resistors, absorbing material at the bottom and each layer is separated by air. The FSS in bottom has good absorption performance at high frequency while the upper layer is used to achieve low‐band absorption. To extend the absorption band to the low frequency, it further add a layer of absorbing material at the bottom. Equivalent circuit is employed to analyze the principle of the designed absorber. The simulation results show that an ultra‐wide absorption band from 0.61 to 12.33 GHz with a fractional bandwidth of 181% is realized for both TE and TM waves under the normal incidence. Furthermore, the thickness of the structure is only 0.07λL, where λL represents the wavelength of the minimum operating frequency. The designed absorber is fabricated and measured, and the measurement is in good agreement with the simulation. [ABSTRACT FROM AUTHOR]

Simultaneous localization and mapping (SLAM) is an essential component for smart robot operations in unknown confined spaces such as indoors, tunnels and underground. This paper proposes a novel tightly-coupled ranging-LiDAR-inertial simultaneous localization and mapping framework, namely RLI-SLAM, which is designed to be high-accuracy, fast and robust in the long-term fast-motion scenario, and features two key innovations. The first one is tightly fusing the ultra-wideband (UWB) ranging and the inertial sensor to prevent the initial bias and long-term drift of the inertial sensor so that the point cloud distortion of the fast-moving LiDAR can be effectively compensated in real-time. This enables high-accuracy and robust state estimation in the long-term fast-motion scenario, even with a single ranging measurement. The second one is deploying an efficient loop closure detection module by using an incremental smoothing factor graph approach, which seamlessly integrates into the RLI-SLAM system, and enables high-precision mapping in a challenging environment. Extensive benchmark comparisons validate the superior accuracy of the proposed new state estimation and mapping framework over other state-of-the-art systems at a low computational complexity, even with a single ranging measurement and/or in a challenging environment. [ABSTRACT FROM AUTHOR]

Ultra-Wideband (UWB) technology is crucial for indoor localization systems due to its high accuracy and robustness in multipath environments. However, Non-Line-of-Sight (NLoS) conditions can cause UWB signal distortion, significantly reducing positioning accuracy. Thus, distinguishing between NLoS and LoS scenarios and mitigating positioning errors is crucial for enhancing UWB system performance. This research proposes a novel 1D-ConvLSTM-Attention network (1D-CLANet) for extracting UWB temporal channel impulse response (CIR) features and identifying NLoS scenarios. The model combines the convolutional neural network (CNN) and Long Short-Term memory (LSTM) architectures to extract temporal CIR features and introduces the Squeeze-and-Excitation (SE) attention mechanism to enhance critical features. Integrating SE attention with LSTM outputs boosts the model's ability to differentiate between various NLoS categories. Experimental results show that the proposed 1D-CLANet with SE attention achieves superior performance in differentiating multiple NLoS scenarios with limited computational resources, attaining an accuracy of 95.58%. It outperforms other attention mechanisms and the version of 1D-CLANet without attention. Compared to advanced methods, the SE-enhanced 1D-CLANet significantly improves the ability to distinguish between LoS and similar NLoS scenarios, such as human obstructions, enhancing overall recognition accuracy in complex environments. [ABSTRACT FROM AUTHOR]

Abstract This paper comprehensively analyses the specific absorption rate (SAR) for an ultra-wideband (UWB) wearable antenna designed for body-centric communication applications. The study is motivated by the extent of electromagnetic radiation in our surroundings, raising worries about health for wireless device users and wearable devices that utilize UWB technology. The proposed antenna is made of a foam substrate having a dielectric constant of 1.07, a thickness of 2 mm with a dimension of $$36\times 48\times 2 {\text{mm}}^{3}$$ 36 × 48 × 2 mm 3 . The designed structure optimizes UWB (3.1–10.6 GHz) in connotation with the ISM band of 2.4 GHz. The proposed antenna works well over the wide frequency range resulting in a bandwidth of 11.53 GHz and a total gain of 8.05 dBi. An excellent impedance matching is obtained by creating a stub at the feed point which gives the maximum value of S11 as − 44.88 dB. The analysis focuses on the SAR values to measure the rate of electromagnetic energy absorption by human tissues over 1 and 10 g by constructing an equivalent three-layer body phantom model. The results indicate that the proposed antenna exhibits SAR values well within the limits set by international standards of 1.6 W/kg averaged over 1 g of tissue and 2 W/kg for 10 g of tissue, while maintaining efficient radiation characteristics across the UWB spectrum.

Accurate indoor robot navigation cannot be achieved without reliable indoor positioning techniques. Ultra-wideband (UWB) is among the most dependable techniques currently available. However, the complexity of indoor environments results in signal transmissions that are susceptible to interference from obstacles, which in turn reduces positioning accuracy. Inertial Navigation System (INS) is an autonomous navigation system that is free from interference in indoor environments and unaffected by non-line-of-sight (NLOS) conditions. This paper proposes a new joint INS and UWB positioning method utilizing the Maximum Correntropy Criterion Kalman Filter (MCCKF). This approach effectively cope with the interference of measurement outliers and extend the design of the adaptive mechanisms to enhance the performance of the localization system. For UWB positioning of tag nodes, an improved Particle Swarm Optimization combined with kmeans (PSO-kmeans) method is used to reduce the impact of NLOS errors on positioning. Finally, the INS is calibrated by AMCCKF fused positioning results. The results of simulations and experiments demonstrate that the proposed AMCCKF fusion algorithm effectively suppresses the impact of anomalous measurements, enhances positioning accuracy and robustness, thereby improving its practicality in real-world environments.

Unmanned aerial vehicles (UAV) are widely used in literature for object detection utilizing convolutional neural networks (CNN). However, most UAVs make use of GNSS sensors for localization, which have low reception in indoor situations. Therefore, this study aimed to investigate the implementation of a multi-UAV object detection system and navigation with the aid of particle swarm optimization (PSO) in ultra-wideband (UWB) positioning systems for GNSS-denied environments, such as inside factories and warehouses. The performance of UWB systems was investigated to determine its viability in the PSO model. An object detection system based on the YOLOv5 network was trained with custom training images and subsequently evaluated with test images. The results of the object detection network were fed as inputs into PSO algorithms. Furthermore, different PSO algorithms were evaluated to determine the suitability for multi-UAV navigation and object detection. The results showed that UWB systems had sufficient accuracy for indoor localization, object detection, and navigation applications. YOLOv5 detection model detected objects with an F1 score of 0.93, given the optimal threshold of 0.8. Regarding the evaluation of PSO algorithms, the stochastic inertia weight variant of PSO algorithms (Sto-IW PSO) performed effectively across all metrics considered in the study compared to other algorithms that only performed effectively in one. Recommendations included the actual implementation of the system with multiple UAVs through field experiments and further refinements to PSO algorithms in order to match the kinematics and response time of the UAVs.

Polarization‐division multiplexing is crucial for increasing channel capacity and spectral efficiency in communications. A key component is the polarization multiplexer, which combines or separates signals with orthogonal polarizations. Existing planar multiplexers lack an ultrawide band for terahertz communications. While microwave‐inspired orthomode transducers (OMTs) provide broadband operation, they suffer from high ohmic loss and bulkiness at terahertz frequencies. Optical integrated polarization beam splitters (PBSs) offer low loss and good integrability but have narrow bandwidths. This work presents a substrateless all‐silicon polarization multiplexer based on tapered directional couplers and air‐silicon effective mediums, integrated monolithically on a compact footprint. The device demonstrates a 37.8% fractional bandwidth, an average insertion loss of ≈$\approx$1 dB, and a polarization extinction ratio above 20 dB over 225–330 GHz. This superior performance is enabled by the anisotropy of the effective medium claddings, affecting the two orthogonal guided modes differently. The multiplexer enables simultaneous two‐channel terahertz fiber communications with polarization diversity.   It supports aggregated data rates up to 155 and 190 Gbit s−1${\rm s}^{-1}$ with bit error rates below hard‐ and soft‐decision forward‐error‐correction limits, respectively. This advancement holds promise for 6G terahertz integrated systems with enhanced channel capacities. [ABSTRACT FROM AUTHOR]

To address the current demands for antenna miniaturization, ultra-bandwidth, and circular polarization in advanced medical devices, a novel ISM band implantable antenna for blood glucose monitoring has been developed. This antenna achieves miniaturization by incorporating slots in the radiation patch and adding symmetric short-circuit probes, resulting in a compact size of only 0.054λ0 × 0.054λ0 × 0.005λ0 (λ0 is the wavelength in free space in respect of the lowest working frequency). By combining two resonance points and utilizing a differential feed structure, the antenna achieves ultra-broadband and circular polarization. Simulations indicate a |S11| bandwidth of 1.1 GHz (1.65–2.75 GHz) and an effective axial ratio (based on 3 dB axis ratio) bandwidth of 590 MHz (1.89–2.48 GHz), able to cover both the ISM frequency band (2.45 GHz) and the mid-field frequency band (1.9 GHz). The antenna exhibits CP gains of −20.04 dBi at a frequency of 2.45 GHz, while it shows gains of −24.64 dBi at 1.9 GHz. Furthermore, a superstrate layer on the antenna's radiating surface enhances its biocompatibility and minimizes its impact on the human body. Simulation and experimental results indicate that the antenna can establish a stable wireless communication link for implantable continuous blood glucose monitoring systems. [ABSTRACT FROM AUTHOR]

Trustworthiness assessment is an essential step to assure that interdependent systems perform critical functions as anticipated, even under adverse conditions. In this paper, a holistic trustworthiness assessment framework for ultra-wideband self-localization is proposed, including the attributes of reliability, security, privacy, and resilience. Our goal is to provide guidance for evaluating a system's trustworthiness based on objective evidence, i.e., so-called trustworthiness indicators. These indicators are carefully selected through the threat analysis of the particular system under evaluation. Our approach guarantees that the resulting trustworthiness indicators correspond to chosen real-world threats. Moreover, experimental evaluations are conducted to demonstrate the effectiveness of the proposed method. While the framework is tailored for this specific use case, the process itself serves as a versatile template, which can be used in other applications in the domains of the Internet of Things or cyber–physical systems. [ABSTRACT FROM AUTHOR]

The labor shortage and rising costs in the greenhouse industry have driven the development of automation, with the core of autonomous operations being positioning and navigation technology. However, precise positioning in complex greenhouse environments and narrow aisles poses challenges to localization technologies. This study proposes a multi-sensor fusion positioning and navigation robot based on ultra-wideband (UWB), an inertial measurement unit (IMU), odometry (ODOM), and a laser rangefinder (RF). The system introduces a confidence optimization algorithm based on weakening non-line-of-sight (NLOS) for UWB positioning, obtaining calibrated UWB positioning results, which are then used as a baseline to correct the positioning errors generated by the IMU and ODOM. The extended Kalman filter (EKF) algorithm is employed to fuse multi-sensor data. To validate the feasibility of the system, experiments were conducted in a Chinese solar greenhouse. The results show that the proposed NLOS confidence optimization algorithm significantly improves UWB positioning accuracy by 60.05%. At a speed of 0.1 m/s, the root mean square error (RMSE) for lateral deviation is 0.038 m and for course deviation is 4.030°. This study provides a new approach for greenhouse positioning and navigation technology, achieving precise positioning and navigation in complex commercial greenhouse environments and narrow aisles, thereby laying a foundation for the intelligent development of greenhouses. [ABSTRACT FROM AUTHOR]

An ultra‐wideband low‐noise amplifier (LNA) design was developed based on distributed network synthesis to achieve impedance matching of an active device by parasitic absorption. The equivalent device models of a low‐noise device were generated using negative‐image device modeling and traveling‐wave matching, and matching circuits were produced using the Chebyshev approximation. The minimum insertion loss and ripple of the matching networks were adjusted correctly to allow the parasitic absorption to match the device models. This paper describes the design methodology for distributed matching circuits and its application to the design of an ultra‐wideband LNA. [ABSTRACT FROM AUTHOR]

In view of the high instantaneous bandwidth requirement of modern electronic countermeasures equipment, a 6~18 GHz ultra wideband T/R module with instantaneous bandwidth of 4 GHz is designed in this study. The MCM(Multi Chip Module) and ultrawideband signal transmission technologies are used to realize the requirements of high integration, miniaturization and modularization of T/R components. The structure of T/R compoments, the index budget of transceiver channel, the simulation of broadband signal transmission characteristics and the design of electromagnetic compatibility are described in detail. The test results show that the T/R module has a good performance in the 12 GHz operating bandwidth, the transmit power is greater than 35 dBm, the receive gain is greater than 20 dB, the noise factor is less than 5 dB, and the total delay time is up to 762 ps. [ABSTRACT FROM AUTHOR]

Over the past years, remote sensing, radar, and imaging applications have all made use of ultra-wideband (UWB) technology. This study undertakes an extensive analysis of tree-shaped monopole antennas tailored for UWB systems. The intended antenna has an incomplete ground plane and a circular radiating patch. To increase bandwidth, two ears have been added to the circular structure. Possessing a dielectric constant of 4.3. The antenna substrate consists of FR-4 material with a dielectric constant of 4.3. To achieve optimal impedance matching for UWB systems, the antenna is fed via a coplanar waveguide (CPW). Design antenna is a simple structure, small size, easy design, and simple integration with the substrate with dimensions of 54 mm ×36 mm ×1.6 mm. All simulation results presented in this article were generated using computer simulation technology (CST) software. He monopole antenna exhibits an impressive impedance bandwidth of 9.6 GHz (146.68%), spanning from 1.99 GHz to 11.56 GHz. Furthermore, the simulated UWB circular monopole antenna exhibits omnidirectional radiation characteristics, boasting a peak gain of 8 dB, and a directivity of 8.2 dBi at the frequency of 5 GHz, and a remarkable radiation efficiency of 97%. With these attributes, the suggested monopole UWB antenna shows significant potential for ground penetrating radar (GPR) applications. [ABSTRACT FROM AUTHOR]

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Near‐infrared (NIR) phosphor‐converted light–emitting diodes (pc‐LEDs) are increasingly used in night vision, surveillance, and biomedicine. A major challenge is to identify a phosphor that efficiently converts blue light into wideband NIR emission. In this paper, a rare‐earth divalent europium (Eu2+)‐activated halogen oxide (Sr3GeO4Cl2) phosphor is unlocked via a high‐temperature solid‐state reaction. The Sr3GeO4Cl2:Eu2+ phosphor emits a wide spectrum (500–950 nm) with a peak at 700 nm when excited by 450 nm blue light. Extended X‐ray absorption fine structure (EXAFS) analysis reveals that the NIR emission primarily originates from Eu2+ ions, and the Eu─O bond length closely resembles the Sr─O bond length. Lattice engineering, specifically Ge/Si cation substitution, increased Eu2+ incorporation into the crystal lattice, boosting luminescence intensity by 75%–122% and quantum efficiency from 15% to 26%. This is related to the combined effect of reduced non‐radiative energy transfer and changes in the local lattice structure of Eu2+. A NIR pc‐LED device using the optimized phosphor showed a photoelectric efficiency of 16.5% and an optical output of 25.07 mW at 100 mA. This study not only explores new Eu2+‐activated NIR phosphors but also highlights the importance of crystal engineering to enhance luminescence properties, guiding future research for efficient NIR pc‐LED development. [ABSTRACT FROM AUTHOR]

With the rapid development of the Internet of Things (IoT), the positioning accuracy requirement of the IoT is increasing, especially for those applications without Global Navigation Satellite System (GNSS) signals. Ultra-Wideband (UWB) is treated as a high-accuracy positioning method that can be utilized in GNSS-blocked environments. However, UWB's performance is still limited when it is applied in practical applications due to errors such as Non-Line-of-Sight (NLOS) errors, multipath errors, and systematic errors in UWB range values. To constrain the impacts of these mentioned errors on UWB positioning accuracy, this work proposes a novel UWB positioning model by introducing a UWB ranging offset calibration algorithm and a moving average filter into a robust extended Kalman filter. In such a UWB positioning model, the ranging offset calibration algorithm is employed to limit the infuence of UWB systematic errors, and the prior residual-based IGG-III weighting model is used to restrain the impacts of NLOS and multipath errors. The moving average filter is to further decrease the impact of the measuring noise on UWB positioning parameter estimation. To investigate the effectiveness of this proposed method, three sets of UWB experiments are arranged in three classic user environments. The experimental results show that (1) after applying the UWB ranging offset calibration algorithm, UWB positioning accuracies in classic environments, namely indoor condition, outdoor condition, and transition area are increased by 50.3%, 20.2%, and 46.9%, respectively; (2) the moving average filter can effectively improve the smoothness of UWB positioning results in terms of standard deviation; (3) the prior residual-based robust theory brings about 49.4% and 25.2% positioning improvements to horizontal and vertical components under poor measurement quality conditions, but such improvements are rather slight when there are good-quality measurements; and (4) after applying the ranging offset calibration algorithm and moving average filter to the robust EKF together, the elevation accuracy of UWB positioning is increased by 67.1%, 22.2%, and 50.5%, respectively, in the three classic user environments. [ABSTRACT FROM AUTHOR]

The paper proposes an ultra-wideband frequency selective rasorber (FSR) with low infrared emissivity for the composite detection threat of both radars and infrared sensors. Firstly, the equivalent circuit (EC) method based on transmission line (TL) theory is utilized to analyze the absorption/transmission conditions. Then, based on the analysis above, sinusoidal microstrip lines with non-frequency-varying characteristics are adopted in the design, which significantly enhances the transmission bandwidth of FSR. The FSR demonstrates an absorption band ranging from 2.65 GHz to 8.80 GHz and a transmission band ranging from 9.15 GHz to 17.71 GHz. Furthermore, an infrared shielding layer (IRSL) exhibiting low emissivity in the infrared band and high transmittance in the microwave band is applied to the FSR. The simulation and experiment results verify that the IRSL-FSR demonstrates an ultra-wide transmission band ranging from 9.16 GHz to 17.94 GHz and an ultra-wide absorption band ranging from 2.66 GHz to 8.01 GHz. Additionally, it exhibits a low emissivity value (0.23) in 8–14 μm, providing a viable solution to the formidable challenge of radar-infrared bistealth for satellites and other communication-enabled flying platforms. [ABSTRACT FROM AUTHOR]

With the continuous development of electromagnetic detection systems, the working frequency of radar gradually expands towards the low-frequency band such as P- and L-band, and the low-frequency horn antenna has also attracted more and more attention. Given the problems of miniaturization, lightweight and ultra-wideband design of low-frequency horn antenna, this paper presents the optimal design for the feed balun, ridge curve, back-feed cavity and sidewall of the traditional horn antenna, and proposes a performance-enhanced double-ridged horn antenna covering 0.21-2.3 GHz. In the entire working band, the antenna has stable radiation patterns and good port-matching characteristics; its VSWR is less than 2 and the main lobes of patterns do not split or deteriorate. The proposed horn antenna can be used as a standard calibration or measurement antenna in antenna or material measurement systems. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to present the simulation, fabrication and testing of a novel ultra-wide band (UWB) band-pass filters (BPFs) with better transmission and rejection characteristics on a low-loss Taconic substrate and analyze using the coupled theory of resonators for UWB range covering L, S, C and X bands for radars, global positioning system (GPS) and satellite communication applications. Design/methodology/approach: The filter is designed with a bent coupled transmission line on the top copper layer. Defected ground structures (DGSs) like complementary split ring resonators (CSRRs), V-shaped resonators, rectangular slots and quad circle slots (positioned inwards and outwards) are etched in the ground layer of the filter. The circular orientation of V-shaped resonators adds compactness when linearly placed. By arranging the quad circle slots outwards and inwards at the corner and core of the ground plane, respectively, two filters (Filters I and II) are designed, fabricated and measured. These two filters feature a quasi-elliptic response with transmission zeros (TZs) on either side of the bandpass response, making it highly selective and reflection poles (RPs), resulting in a low-loss filter response. The transmission line model and coupled line theory are implemented to analyze the proposed filters. Findings: Two filters by placing the quad circle slots outwards (Filter I) and inwards (Filter II) were designed, fabricated and tested. The fabricated model (Filter I) provides transmission with a maximum insertion loss of 2.65 dB from 1.5 GHz to 9.2 GHz. Four TZs and five RPs are observed in the frequency response. The lower and upper stopband band width (BW) of the measured Filter I are 1.2 GHz and 5.5 GHz of upper stopband BW with rejection level greater than 10 dB, respectively. Filter II (inward quad circle slots) operates from 1.4 GHz to 9.05 GHz with 1.65 dB maximum insertion loss inside the passband with four TZs and four RPs, which, in turn, enhances the filter characteristics in terms of selectivity, flatness and stopband. Moreover, 1 GHz BW of lower and upper stopbands are observed. Thus, the fabricated filters (Filters I and II) are therefore evaluated, and the outcomes show good agreement with the electromagnetic simulation response. Research limitations/implications: The limitation of this work is the back radiation caused by DGS, which can be eradicated by placing the filter in the cavity and retaining its performance. Practical implications: The proposed UWB BPFs with novel resonators find their role in the UWB range covering L, S, C and X bands for radars, GPS and satellite communication applications. Originality/value: To the best of the authors' knowledge, for the first time, the authors develop a compact UWB BPFs (Filters I and II) with BW greater than 7.5 GHz by combining reformed coupled lines and DGS resonators (CSRRs, V-shaped resonators [modified hairpin resonators], rectangular slots and quad circle slots [inwards and outwards]) for radars, GPS and satellite communication applications. [ABSTRACT FROM AUTHOR]

Indoor and outdoor positioning systems are difficult to locate in large areas and complex environments. In order to compensate for the impact of indoor and outdoor scene transformation, an indoor and outdoor positioning system based on GNSS/UWB/IMU is proposed, which can realize seamless and high-precision positioning between buildings in mixed scenes. In view of this, GNSS and IMU fusion is used outdoors for Error-State Kalman Filter (ESKF) filtering for positioning. At the same time, this paper proposes a D-CEP algorithm to analyze the UWB ranging variance offline and improve the accuracy of UWB positioning data. In the mixed scene, the UWB and GNSS information are tightly coupled and nonlinearly optimized to improve the positioning accuracy and achieve seamless connection between indoor and outdoor staggered scenes. Indoor and outdoor scenes use UWB and IMU fusion for ESKF filtering to achieve indoor and outdoor high precision. In indoor complex scenes, due to the existence of Ultra-wideband non line of sight (UWB-NLOS) error, the observation data may be discontinuous. When the number of observed signals is less than the number required for nonlinear optimization, the UWB-NLOS error is compensated by IMU prior information, and the positioning data is obtained to make up for the lack of positioning data and realize indoor and outdoor seamless positioning. Compared with the traditional filtering method, the average positioning accuracy is improved by 40.97 % (the Mean Absolute Error is increased from 0.256336 m to 0.151308 m). Compared with the state-of-the-art LiDAR-SLAM (LIO-SAM), the approximate positioning result can be obtained (ESKF-UWB-NLOS Mean Absolute Error is 0.151308 m, LiDAR-SLAM Mean Absolute Error is 0.148853 m). [ABSTRACT FROM AUTHOR]

The increasingly complex electromagnetic environment of modern warfare and the proliferation of intelligent jamming threaten to reduce the survival rate of radio fuzes on the battlefield. Radio frequency (RF) stealth technology can fundamentally improve the anti-interception and reconnaissance capabilities of radio fuzes, thereby lessening the probability of them being intercepted, recognized, and jammed by the enemy. In this paper, an RF stealth waveform based on chaotic pulse-position modulation is proposed for ultra-wideband (UWB) radio fuzes. Adding a perturbation signal based on the Tent map ensures that the chaotic sequences have sufficiently long periods despite hardware byte limitations. Measuring the approximate entropy and sequence period shows that the Tent map with the addition of perturbation signals can maintain good randomness under byte constraints, closely approximating the Tent map with ideal precision. Simulations verify that the proposed chaotic mapping used to modulate the pulse position of an ultra-wideband radio fuze signal results in superior detection, anti-interception, and anti-jamming performance. [ABSTRACT FROM AUTHOR]

In modern communication systems, ultra-wideband (UWB) technology has garnered substantial attention due to its superior attributes compared to traditional narrowband communication systems. Over the past decade, UWB technology has also found applications in microwave-based imaging systems. This study introduces a simple planar coplanar waveguide-fed circular shape arc slot antenna designed specifically for biomedicine and microwave medical imaging applications. The proposed design is implemented on a 1.6-mm-thick FR4 substrate with a relative permittivity of 4.4 and a loss tangent of 0.0009. The antenna has physical dimensions of 26 mm × 29 mm and achieves an impressive bandwidth of 16.6 GHz, spanning 2.4 to 19 GHz. It exhibits a peak gain of 2.5 dBi and consistent omnidirectional radiation characteristics. Thorough temporal analysis validates the antenna's performance within acceptable limits, which is further affirmed through practical fabrication and testing, demonstrating strong agreement with simulation results. [ABSTRACT FROM AUTHOR]

The paper describes a high-gain ultra-wideband (UWB) elliptical and circular slotted antipodal Vivaldi antenna (ECS-AVA) that is designed for through-wall detection systems. The antenna flares are loaded with elliptical and circular slots to improve the gain and broaden the bandwidth. To validate the efficacy of the designed antenna, a prototype of ECS-AVA is fabricated and subjected to measurements. The experimental findings suggest that the designed antenna can handle signals effectively across a range from 3.1 GHz to 10.6 GHz, as shown by its measured impedance bandwidth, with |S11|≤ -10 dB. The obtained measurements results are consistent with the results of the CST simulation. The proposed antenna exhibits improved radiation patterns in the UWB band with peak gain values ranging from 4.8 dB to 11.9 dB. [ABSTRACT FROM AUTHOR]

Addressing the power supply challenges of wireless sensor nodes is pivotal for advancing the development of the Internet of Things (IoT). This work proposes a high performance and stackable trampoline like‐triboelectric vibration energy harvester (T‐TVEH) that can efficiently harvest ultra‐wideband vibrational energy for in‐situ powering of sensor nodes. The unique structural design and material selection enables T‐TVEH to represent a breakthrough in terms of both working bandwidth and power density compared to recent research efforts of vibration energy harvesting. Specifically, the working bandwidth and the peak power density of T‐TVEH is 192 Hz and 5.9 W m−2, which are higher than previous related studies by 156% and 59.2%, respectively. Based on the excellent performance of the T‐TVEH, a wireless sensor node for monitoring machinery condition is constructed. Temperature, humidity, and frequency information are successfully acquired and transmitted to 1000‐m through the wireless sensor node, which is nine times improved compared to related studies. Meanwhile, it achieves fully self‐powered wireless operation monitoring and abnormal alarm on a real ship's marine diesel engine. Overall, this study proposed an innovative solution for in‐situ power supply of wireless sensor nodes, which has broad application prospects in the field of the IOT. [ABSTRACT FROM AUTHOR]

The ultra-wideband (UWB) technology has been increasingly recognized as an efficacious strategy for Indoor Positioning Systems (IPSs). However, the accuracy of the UWB system can be severely degraded by non-line-of-sight (NLOS) errors. In this study, we proposed a new method to reduce the UWB positioning error in such an indoor environment. We developed a system consisting of a Robotic Total Station (RTS), four UWB base stations, a moving target (including a prism and a UWB tag), and a PC. The observed coordinates of the moving target, captured using millimeter precision from an RTS device, served as the ground truth for calculating the positioning errors of the UWB tag. In a significant NLOS scenario, the UWB's three-dimensional positioning error was identified to exceed the nominal value declared by the manufacturer by a factor of more than three. A detailed analysis revealed that each coordinate component's error distribution pattern demonstrated considerable variance. To reduce the NLOS error, we designed a combined multilayer neural network that simultaneously fits errors on all three coordinate components and three separate multilayer networks, each dedicated to optimizing errors on a single coordinate component. All networks were trained and verified by benchmark errors obtained from the RTS. The results showed that neural networks outperform the traditional methods, attributed to their strong nonlinear modelling ability, thereby significantly improving the external accuracy by an average reduction in RMSE by 61% and 72%. It is evident that the proposed separate networks would be more suitable for NLOS positioning problems than a combined network. [ABSTRACT FROM AUTHOR]

An efficient design method for a compact and ultra-wideband multi-stage Wilkinson power divider in a parallel stripline (PSL) is proposed. To enhance the frequency bandwidth of the proposed power divider while reducing its size, the isolation branch is modified; that is, two capacitors are connected to both sides of a resistor at each isolation branch. For an efficient design process, the PSL power divider is equivalently represented by two microstrip power dividers, and the design equations are derived. Based on the design equations, an in-house algorithm is utilized to optimally determine the design parameters, including the line impedance, resistance, and capacitance of each stage. For example, a three-stage PSL power divider is designed with three λ / 4 transmission lines at a base frequency of 5 GHz. To verify the accuracy of the design procedure, 3D EM simulations and measurements are performed, and the results show good agreement. Compared with the conventional three-stage Wilkinson power divider, the proposed PSL power divider achieves a wider frequency bandwidth of 1.16 to 6.51 GHz (139.5%) and a 23% shorter transmission line length of 207°, while exhibiting an insertion loss of 0.7 to 1.4 dB. [ABSTRACT FROM AUTHOR]

The technology, design procedure, and measurements of an ultra‐wideband (UWB) push–pull high‐performance complementary metal‐oxide semiconductor (CMOS) low‐noise amplifier (LNA) are presented in this letter. While the push–pull LNA exhibits commendable direct current (DC) power consumption, its operational bandwidth is often limited by the inherent parasitic parameters of the transistors. To exploit the parasitic parameters of the transistors, a multipole‐tuning circuit that utilizes pole‐tuning inductors and parasitic capacitors of the MOS to extend the operational bandwidth is proposed. A UWB LNA is implemented using a commercial 40‐nm CMOS process, and the measurement results demonstrate a peak gain of 20.2 dB, an exceptionally wide bandwidth of 0.5–7.5 GHz, a noise figure of 4 dB, and an output power of 3.5 dBm at OP1 dB with 7.2 mW DC power consumption. The chip area of the LNA is a compact 0.26 mm2. Experimental results closely align with simulations, confirming the validity of the concept and showcasing its competitive performance. [ABSTRACT FROM AUTHOR]

In order to realize unmanned cluster intelligent inspection, a channel estimation method is proposed to deal with the multipath effect in complex environment, aiming at the disadvantages of pulse UWB technology in complex areas such as mountain and forest. Through theoretical analysis and experimental research, a channel estimation method (TS-SC) based on the fusion of tree wavelet compression and maximum likelihood method is proposed. Based on the Bayesian compressed sensing (CS) model, the hierarchical Bayesian model is established through sparse matrix of wavelet base and Markov chain Monte Carlo sampling to realize the recovery of the original signal under low-speed sampling. Then, the maximum likelihood estimation method (SC) is used to accurately estimate the number and gain of multipath. The experimental results show that under the condition of noise SNR is 10 dB, the detection accuracy can reach 0.559 2 with the help of low frequency sampling data, which meets the requirement of channel estimation in complex environment. The research results break through the limitations of traditional channel estimation methods and provide an effective solution for UAV cluster communication in complex environments. [ABSTRACT FROM AUTHOR]

This article introduces an innovative circular and compact ultra‐wideband (UWB) radiator designed specifically for 5G microwave applications. This antenna incorporates a “TU”-shaped ground plane on its reverse side, with strip lines feeding the circular element on the front side. Notably, the antenna exhibits impressive characteristics, including an outstanding impedance bandwidth of 107%, and an impressive return loss of -32 dB. Its operational frequency range spans from 2.4 GHz to 11 GHz, centered at 6.7 GHz. Extensive simulations were conducted using CST microwave studio software to validate its performance. The antenna’s physical dimensions are defined by a size of 0.12 λ × 0.08 λ × 0.012 λ relative to its wavelength. Furthermore, this antenna demonstrates exceptional stability in its polar patterns and maintains a high-efficiency level, achieving a substantial gain of 3.75 dBi with an efficiency rating of 84.5%. These remarkable attributes make this antenna suitable for a wide range of applications, including Wi-Fi, 5G, WLAN, and various other microwave communication scenarios. [ABSTRACT FROM AUTHOR]

In this manuscript, the design of a compact-size circular patch Ultra-Wideband (UWB) antenna with enhanced fractional bandwidth (BW), peak realized gain (PRG), and proper impedance matching is presented. The modified antenna has three circular slots etched from the circular path (top), fed by a 50O microstrip feed line. These circular slots play a significant role in improving the impedance bandwidth. Additionally, the partial ground plane with a slot integrated with a rectangular stub is used in order to achieve a bandwidth for an operating range of 3.25 GHz - 27 GHz. The proposed antenna is designed, fabricated, and tested in the laboratory in order to validate with simulation data. The designed antenna size is 25 mm? 20 mm × 0.508 mm. The experimental value of 10 dB return loss absolute/fractional BW of 23.75 GHz/157.08% at the center frequency, minimum/maximum gain of 5.90/12.05 dBi, and maximum/minimum radiation efficiency of 85/97 % are achieved from the 3.25 GHz to 27 GHz frequency range. In addition, a comparison table is provided to prove the state-of-the-art of the antenna's design. The proposed antenna is suitable for wireless services, radar, and satellite communication. [ABSTRACT FROM AUTHOR]

Indoor positioning is a key technology in today's intelligent environments, and it plays a crucial role in many application areas. This paper proposed an unscented Kalman filter (UKF) based on the maximum correntropy criterion (MCC) instead of the minimummean square error criterion (MMSE). This innovative approach is applied to the loose coupling of the Inertial Navigation System (INS) and Ultra-Wideband (UWB). By introducing the maximum correntropy criterion, the MCCUKF algorithm dynamically adjusts the covariance matrices of the system noise and the measurement noise, thus enhancing its adaptability to diverse environmental localization requirements. Particularly in the presence of non-Gaussian noise, especially heavy-tailed noise, the MCCUKF exhibits superior accuracy and robustness compared to the traditional UKF. The method initially generates an estimate of the predicted state and covariance matrix through the unscented transform (UT) and then recharacterizes the measurement information using a nonlinear regression method at the cost of theMCC. Subsequently, the state and covariance matrices of the filter are updated by employing the unscented transformation on the measurement equations. Moreover, to mitigate the influence of non-line-of-sight (NLOS) errors positioning accuracy, this paper proposes a k-medoid clustering algorithm based on bisection k-means (Bikmeans). This algorithm preprocesses the UWB distance measurements to yield a more precise position estimation. Simulation results demonstrate that MCCUKF is robust to the uncertainty of UWB and realizes stable integration of INS and UWB systems. [ABSTRACT FROM AUTHOR]

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Abstract Sociopositive interactions with conspecifics are essential for equine welfare and quality of life. This study aimed to validate the use of wearable ultra-wideband (UWB) technology to quantify the spatial relationships and dynamics of social behaviour in horses by continuous (1/s) measurement of interindividual distances. After testing the UWB devices’ spatiotemporal accuracy in a static environment, the UWB measurement validity, feasibility and utility under dynamic field conditions was assessed in a group of 8 horses. Comparison of the proximity measurements with video surveillance data established the measurement accuracy and validity (r = 0.83, p

Equivalent-time sampling can improve measurement or sensing systems because it enables a broader frequency band and higher delay resolution for periodic signals with lower sampling rates than a Nyquist receiver. Meanwhile, a digital down-conversion (DDC) technique can be implemented using a straightforward radio frequency (RF) circuit. It avoids timing skew and in-phase/quadrature gain imbalance instead of requiring a high-speed analog-to-digital converter to sample an intermediate frequency (IF) signal. Therefore, when equivalent-time sampling and DDC techniques are combined, a significant synergy can be achieved. This study provides a parameter design methodology for optimal equivalent-time sampling using DDC.

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A design method for an ultra-wideband coplanar-stripline-based vertical transition that can be used for ultra-high-speed digital interfaces is proposed. A conventional via structure, based on a differential line (DL), inherently possesses performance limitations (<10 GHz) due to difficulties in maintaining constant line impedance and smooth electric field transformation, in addition to the effects of signal skews, FR4 fiber weave, and unbalanced EM interferences. DL-based digital interfaces may not meet the demands of ultra-high-speed digital data transmission required for the upcoming 6G communications. The use of a coplanar stripline (CPS), a type of planar balanced line (BL), for the vertical transition, along with the ultra-wideband DL-to-CPS transition, mostly removes the inherent and unfavorable issues of the DL and enables ultra-high-speed digital data transmission. The design process of the transition is simplified using the analytical design formulas, derived using the conformal mapping method, of the transition. The characteristic line impedances of the transition are calculated and found to be in close agreement with the results obtained from EM simulations. Utilizing these results, the CPS-based vertical transition, maintaining the characteristic line impedance of 100 Ω, is designed and fabricated. The measured results confirm its ultra-wideband characteristics, with a maximum of 1.6 dB insertion loss and more than 10 dB return loss in the frequency range of DC to 30 GHz. Therefore, the proposed CPS-based vertical transition offers a significantly wider frequency bandwidth, i.e., more than three times that of conventional DL-based via structures. [ABSTRACT FROM AUTHOR]