Ultra-wideband Range Research Articles

Biomimetic Ambient‐Pressure‐Dried Aerogels with Oriented Microstructures for Enhanced Electromagnetic Shielding

AbstractOriented aerogels, emerging as a new generation of lightweight electromagnetic interference (EMI) materials, often face complex synthesis processes. While creating an orderly oriented microstructure for EMI aerogels through ambient pressure drying (APD) shows promise, it remains a significant challenge. Here, inspired by the directional grown structure of the plant, a new strategy that employs rapid precursor orientation followed by slow cross‐linking to achieve the APD of directional EMI aerogels is proposed. This approach demonstrates that low‐temperature oriented polymerization of polyaniline enables strong cross‐linking with poly(3,4‐ethylenedioxythiophene) and alginate, forming a robust conductive directional skeleton and mitigating surface tension issues during mild drying. The resulting aerogel features high conductivity (48.84 S m−1), excellent flame retardancy, and impressive compressive strength. Notably, its sturdy frame allows for further enhancement with other functional materials, such as Mxene, through re‐processing and re‐drying. The tree‐branch‐like aerogel achieves a significantly improved EMI shielding effectiveness of 50.3 dB across an ultrawideband range of 8.2–40 GHz. This strategy offers a new idea for the straightforward preparation of functional aerogels with programmability and oriented microstructures using ambient drying.

Graphene‑vanadium dioxide ultra-wideband dual regulated absorber

In this paper, we propose a novel tunable THZ absorber consisting of a patterned graphene layer and a metal plate separated by a vanadium dioxide dielectric layer. The absorbent has a simple structure, is easy to make graphene patterns, and has a dual regulatory function. The ability to double regulate comes from the fact that the state of vanadium dioxide changes with the temperature between the insulating phase and the metal phase, resulting in a change in its conductivity. When vanadium dioxide is in the insulating phase, the total reflection characteristics of the absorber are >7 THz, and when vanadium dioxide is in the metallic phase, the absorber achieves near-perfect absorption in the ultra-wideband range of 3 THz to 12.4 THz (9.4 THz). Local surface plasmon resonance explains the perfect absorption. Compared with previous absorbers, our proposed absorbers are not only simple in structure, the graphene pattern is also easy to process, but also have double adjustment and perfect absorption in the ultra-wideband range, are not sensitive to polarized light, and have large tolerances for the Angle of incident. The further development and enrichment of terahertz metamaterials and metasurface devices will also have beneficial implications for terahertz wave applications in sensing, communications, and radar. Due to their significant application value in stealth, detection, and communication, metamaterial absorbers have become a research hotspot in the field of metamaterials.

Ranging Offset Calibration and Moving Average Filter Enhanced Reliable UWB Positioning in Classic User Environments

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.

A novel UWB/INS tight integration model based on ranging offset calibration and robust cubature Kalman filter

Ultra-wideband (UWB) is treated as a competitive positioning technology for indoor location-based applications. However, the non-line-of-sight (NLOS) condition would lead to a UWB solution with low accuracy and poor stability. Such an influence of NLOS errors on UWB positioning accuracy can partially be degraded after integrating UWB range measurements with measurements from an inertial navigation system (INS). Compared with the loose integration based on UWB positioning solutions and the INS-predicted solutions, such a tight integration of UWB/INS has significant advantages in operating with the number of available UWB measurements less than three and detecting and reducing the influence of NLOS errors. However, the accuracy of such a UWB/INS tight integration in the vertical direction is still poor due to the distribution of UWB base stations and UWB ranging offsets. To solve these problems in UWB positioning, this paper proposes a robust and reliable UWB/INS tight integration method based on a ranging offset calibration model and an improved robust cubature Kalman filter (IRCKF), in which the impacts of UWB ranging offsets, NLOS errors, and linearization errors are constrained. According to the results based on a set of experiment data, about 4.3 % and 54.2 % position improvements in horizontal and vertical directions can be obtained by applying ranging offset calibration in UWB positioning mode. Such positioning improvements obtained by applying the IGG-III robust model are about 51.0 % and 2.8 % in horizontal and vertical directions. Furthermore, the CKF offers about 16.0 % and 6.1 % positioning improvements in horizontal and vertical directions, compared to that of EKF. In general, the IRCKF-based UWB/INS tight integration has an accuracy of 0.082 m, 0.841 m, 0.493°, 0.468°, and 5.785° in horizontal position, vertical position, roll angle, pitch angle, and heading angle, respectively, which offers about 65.8 %, 58.9 %, 27.3 %, 26.4 %, and 46.5 % improvements percentages compared to the solutions from the EKF-based UWB/INS tight integration.

Enhancing RF energy harvesting in smart cities with two port MIMO-UWB antenna design using machine learning algorithms

Abstract This work presents the two port ultra-wide band MIMO antenna with novel isolation structure and dual band RF Rectifier for 3.3 GHz and 4.65 GHz frequencies for RF energy harvesting applications. The anticipated antenna is systematically examined within the ultra-wideband (UWB) range from 3.1 GHz to 10.6 GHz design frequency with four different steps: Antenna 1, Antenna 2, Antenna 3 and Antenna 4 (optimal design) are chosen for comprehensive study. A unique isolation structure was developed between two identical elements separated by 10 mm, resulting in an enhanced isolation of −23.5 dB at 3.15 GHz, −27 dB at 5.8 GHz, −28 dB at 9.26 GHz and greater than −34 dB at 7.5 GHz. The suggested antenna resonates at UWB band and have fractional bandwidth of 118.66 % and a peak gain of 4.1 dB at 3.15 GHz, 3.68 dB at 5.8 GHz, 6.4 dB at 7.5 GHz and 3.2 dB at 9.26 GHz has been obtained. Radiation efficiencies of 92.5 %, 95 %, 90 % and 84.5 % at 3.15 GHz, 5.8 GHz, 7.5 GHz and 9.26 GHz were obtained respectively. The recommended MIMO performance is simulated using HFSS in terms of ECC, DG, MEG and CCL. The results adhere to specified requirements and confirmed by experimentation. An HFSS simulated dataset of reflection coefficient is used as input for the various ML algorithms namely, Support Vector Machine (SVM), Ensemble, k-nearest neighbors’ algorithm (KNN) and Gaussian Process Regression (GPR) models are trained with 80 % of the data and testing with 20 % of the data. The test results are compared and corresponding performance values of MAE, RMSE, MSE & R 2 are 0.00029, 0.00197, 3.87e−6 and 1.0 validation results and corresponding test results are 0.00031, 0.00229, 5.20e−6 and 0.999. Finally, the proposed dual band rectifier with a shorted stub is tested for harvesting applications at 3.3 GHz and 4.65 GHz frequency and it attained RF to DC conversion efficiencies of 69 % and 55.40 % respectively.

DESIGN OF HIGHLY ISOLATED UWB MIMO ANTENNA USING STUBS BETWEEN GROUND PLANES

This study introduces an in-depth analysis and evaluation of a novel High-Isolation Ultra-Wideband (UWB) Multiple Input Multiple Output (MIMO)antenna design featuring the integration of Stubs between ground planes.The objective is to develop an antenna system capable of achieving high isolation between closely spaced antenna elements for MIMO applications while maintaining a wide operating bandwidth. The proposed antenna is composed of four slot antenna elements with a common rhombic slot, each fed by a microstrip-fed line to greatly reduce the overall size of the antenna.It has a compact size of (34 x 34 x 1.6 mm3).The wide frequency range of Ultra-wide band lies in the range of 3.1 to 10.6 GHz and wide channel bandwidths of 500 MHz.The combination of ultra-wideband multiple-input and multiple-output(UWB MIMO) technology has high transmission rate,good communication quality and large channel capacity.Investigation will be done with respect to correlation parameter coefficients,radiation characteristics,efficiency,realized gain and the active reflection coefficient. In essence,the Highly Isolated MIMO Antenna marks a significant stride in antenna technology and in the field of wireless communication.CST(Computer Simulation Technology) is used to design the proposed antenna. Keywords-Antenna,Isolation,UWB,MIMO,Stubs,S-Parameter Results.

A high sensitivity planar electric–magnetic isolated sensor for full characterization of magneto-dielectric materials

Magneto-dielectric (MD) materials have received much attention due to their applications in design of high-performance antenna and microwave components. Usually, their permittivity and permeability are key parameters in design of these components. Unfortunately, full characterization of these parameters faces challenge of measurement coupling between permittivity and permeability. To address this issue, an electric and magnetic isolated sensor based on a planar resonance structure is proposed and verified. Several shorting pins are used to separate the electric and magnetic regions, which effectively reduces the measurement coupling between permittivity and permeability. These shorting pins form a magnetic cavity pins (MCP) structure. The resonance structure is used for permittivity measurement, and the MCP structure is designed for measuring permeability with enhanced sensitivity. Moreover, to further improve the quality factor, a metal patch and two 50 Ω chip resistors are integrated on the microstrip line. To extract the imaginary part, the quality factor calculated from S21 will be used. By integrating these techniques, the sensor developed in this paper provides possibility of full characterization of MD materials with high sensitivity. Moreover, the magnetic cavity provides more space than the original design, allowing measurement in the Ultra-Wideband (UWB) range possible. Two sensors are designed and fabricated for validating the sensitivity and accuracy. Several materials with different permittivity and permeability are measured. The extracted measurement values show high agreement with the reference values. The permeability errors for real and imaginary parts are smaller than 3% and 4.5%, respectively. And the permittivity errors are smaller than 2.6% and 6.4%.

Notch band characteristics improvement of a printed ultra wideband antenna by embedding frequency Selective Surface

Excellent improvement on band notched characteristics of a circular ultra-wideband (UWB) printed antenna by embedding Frequency Selective Surface (FSS) at proper position in the far field is presented in this article. A square shaped mushroom Electromagnetic Band Gap (EBG) structure is placed beside the feeding line to achieve an elimination band of 3.7–4.2 GHz over the ultra-wideband range of 2.9–14 GHz showing fractional bandwidth of 131 %. The proposed antenna's electrical dimension is 0.29λ×0.367λ×0.015λ. After embedding the properly designed FSS at optimal position along with the antenna the maximum gain of the radiating frequency increases from 7.1 dBi to 8.1 dBi and notch frequency gain reduces to −7.9 dBi from −5 dBi. Radiation efficiency at notch frequency also reduces from 31 % to 17 %. More than 10 dB Front to Back lobe Ratio (FBR) is obtained at 4.5 GHz. With the aid of Advanced Design Software (ADS), an equivalent circuit for the suggested antenna is created and its response is contrasted with measured and simulated outcomes. The proposed antenna is useful in UWB range with band rejection for C band satellite downlink.

Multifunctional metasurface for ultrafast all-optical efficient modulation of terahertz wave

Metasurfaces have been widely used to terahertz (THz) modulators due to their unique electromagnetic (EM) modulation properties. However, to realize ultrafast and efficient control of the active metasurfaces remains a critical challenge. Herein, we first demonstrate a multifunctional metasurface modulator based on metal square rings, which have central rotational symmetry with local asymmetry. The former captures more EM energy to achieve strong enhancement of the local EM responses, and the latter generates high quality factor (Q-factor) Fano resonance. By scaling the unit structure, the resonant frequency shifts in an ultra-wideband range of ∼0.29-10 THz, which shows a linear relation between the Q-factor and the scaling factor, and an exponential variation between the full width at half maximum (FWHM) and the scaling factor. The results provide an effective approach to predict the frequency selection characteristics of the modulators in the THz regime. More importantly, by embedding the silicon into the specific position of the metasurface, external optical control results in the unit structure is constructed from meta-atom to molecularization model, the shifting of resonant frequency and the multi-level modulation of amplitude are realized, and the maximum modulation depth (MD) reaches ∼100 %. By systematically studying the dynamics of frequency and amplitude regulation, benefiting from the ultra-short relaxation time of the photo-carriers in silicon bridge, an ultrafast full recovery time of 2000 ps is achieved. Combined with the local field characteristics, the scaled unit structure achieves efficient modulation of the resonant frequency and amplitude under optical pumping, which provides a promising approach for the development of active metasurface modulator suitable for the whole THz band. This work demonstrates the viability of optical control molecularization of specific meta-atoms is applicable to the entire THz band, which has great potential use for future state-of-the-art THz modulators.

Ultra-conformal epidermal antenna for multifunctional motion artifact-free sensing and point-of-care monitoring

Accurate acquisition of physiological and physical information from human tissue is essential for health monitoring, disease prevention and treatment. The existing antennas with traditional rigid or flexible substrates are susceptible to motion artifacts in wearable applications due to the miniaturization limitation and lack of proper adhesion and conformal interfaces with the skin. Recent advances in wearable radio frequency (RF) bioelectronics directly drawn on the skin are a promising solution for future skin-interfaced devices. Herein, we present a first-of-its kind epidermal antenna architecture with skin as the antenna substrate, which is ultra-low profile, ultra-conformal, ultra-compact, and simple fabrication without specialized equipment. The radiation unit and ground of antenna are drawn directly on the skin with the strong adhesion and ultra conformality. Therefore, this RF device is highly adaptable to motion. As a proof-of- feasibility, epidermal antenna can be freely drawn on demand at different locations on the skin for the development of temperature sensor, skin hydration sensor, strain sensor, glucose sensor and other devices. An epidermal antenna-based temperature sensor can offer accurate and real-time monitoring of human body temperature changes in the ultra-wideband (UWB) range. The results during the monitoring of hydration level with and without stretching show that the epidermal antenna drawn on the skin is motion artifact-free. We also designed an epidermal antenna array employing a horseshoe-shaped configuration for the precise identification of various gestures. In addition, the non-invasive blood glucose level (BGL) monitoring results during the in-vivo experiments report high correlation between the epidermal antenna responses and BGLs, without any time hysteresis. After the prediction of BGL by BP network, all the predicted BGL values are fallen 100% into the clinically acceptable zones. Together, these results show that epidermal antenna offers a promising new approach for biosensing platform.

GRVINS: Tightly Coupled GNSS-Range-Visual-Inertial System

Bridge inspection is currently a labor intensive task. Utilizing unmanned aerial vehicles (UAVs) to assist in inspection tasks is a promising direction. However, enabling UAVs for autonomous inspection involves the UAV state estimation problems. Since parts of UAV sensors could be unavailable, how to estimate states via sensor fusion is the key. In this paper, we propose a tightly-coupled nonlinear optimization-based system that integrates four kinds of sensors: camera, IMU, Ultra-wideband (UWB) range measurements, and global navigation satellite system (GNSS). Due to the tightly-coupled multi-sensor fusion method and system design, the system takes the advantage of the four sensors, and can seamlessly respond to indoor and outdoor GNSS and UWB loss or reacquisition. It can effectively reduce the long-term trajectory drift and provide smooth and continuous state estimation. The experimental results show that the proposed method outperforms the state-of-the-art approaches.

Optimizing ultra-wideband balanced power amplifiers through the selection of different output impedance transformation based on SiP techniques

In this paper, two improved ultra-wideband (UWB) balanced power amplifiers based on the flip-chip system-in-package technique and electronic design automation (EDA) are proposed. The conventional approach to system-on-chip (SoC) involves integrating all sub-circuit designs into a single manufacturing process. However, in radio frequency circuits, adopting the SoC approach necessitates intricate matching designs, leading to an increase in development costs. In this study, two types of SiGe unit power amplifiers attempted to achieve a flat S21 response using simpler matching for input/output. The cascode architecture was adopted as the main structure for the first type of unit power amplifier (type I). Subsequently, the design of the second type unit power amplifier was built upon the foundation of the first type, with the only difference being the implementation of two parallel cascode structures (type II), and the primary goal is to enhance both gain and output power compared to the first type. In addition, for this second type unit power amplifier, in conjunction with a quadrature hybrid coupler, the optimal impedance matching value was selected to maintain the flatness of gain across the entire UWB range. Furthermore, the poor performance of S11,22 of these two types of unit power amplifiers was improved by using quadrature hybrid couplers using the WIPD process combined with EDA simulation. Therefore, using flip-chip packaging technology can effectively reduce the increased wafer fabrication costs caused by complex matching designs in active circuits. This improved system has the potential to offer a new practical application for UWB power amplifier design.

Quasi-elliptic band pass filter using resonators based on coupling theory for ultra-wide band applications

PurposeThis 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/approachThe 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.FindingsTwo 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/implicationsThe 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 implicationsThe 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/valueTo 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.

Temperature-tunable terahertz metamaterial device based on VO2 phase transition principle.

Terahertz devices play an irreplaceable role in the development of terahertz technology. However, at present, it is difficult for most natural materials to respond in the terahertz band, making the devices made of them perform poorly. In order to realize the diversity and tunability of device functions, we designed a terahertz metamaterial device composed of the thermally-induced phase change material VO2. The device structure is composed of a Au bottom layer, a SiO2 dielectric layer and a VO2 top layer. Through software simulation, we found that when T = 313 K, the device has complete reflection ability in the whole terahertz band. When T = 342 K, the average absorptivity is above 95% in the ultra-wide band range of 4.71-9.41 THz, and the absorptivity reaches an amazing 0.99999 at 6.31 THz. Thus, the maximum thermal modulation range of the device is 0.001-0.99999. The Bruggeman effective medium theory clarifies the phase transition characteristics of vanadium dioxide. The Drude model establishes the functional relationship between the conductivity of vanadium dioxide and temperature. The basic principle of high absorption was described using the impedance matching theory. We also drew the electric field intensity diagram during the temperature rise of the device to further confirm the reason for the change in the device performance. In addition, the influence of the absence of different structural layers on the absorptivity was simulated, which reflected the role of each layer structure more intuitively. We also explored the influence of the geometric size of the device on the absorptivity, which provided a certain reference value for practical application. In short, we have designed a tunable terahertz device with simple structure, high absorptivity, and wide absorption bandwidth, which can be used in the fields of energy collection, electromagnetic stealth, and modulation.

A Synthetic Ultra-Wideband Range Profiling Method for High-Speed Targets Based on Phase-Derived Velocity Measurement

A Synthetic Ultra-Wideband Range Profiling Method for High-Speed Targets Based on Phase-Derived Velocity Measurement

Design and performance analysis of a mid-infrared broadband thermally tunable metamaterial absorption device based on the phase-change effect.

We propose a structurally simple, innovative, and multifunctional mid-infrared broadband thermally tunable metamaterial absorption device. The absorption device consists of a three-layer structure, from bottom to top: Ti substrate, SiO2 dielectric layer, and patterned VO2 layer. Through temperature control, the average absorption intensity of the absorption device can vary between 0.08 and 0.94. The absorption device's absorption mechanism is rooted in the thermal phase-change characteristics exhibited by the topologically patterned VO2. When the temperature is below 340 K, VO2 is in a dielectric state, resulting in near-total reflection performance in the mid-infrared range. When the temperature is above 340 K, VO2 undergoes a dielectric-to-metal transition, enabling the absorption device to achieve an average absorption rate of 94.12% in the ultra-wideband range of 6.26 μm-20.96 μm in the mid-infrared. This absorption range completely covers the atmospheric window wavelengths of 8 μm-14 μm, demonstrating high practical value. We explain the working mechanism of the absorption device from the perspective of the electromagnetic field. Subsequently, we study the variations in the absorption curve of the absorption device at different temperatures of VO2 and use the changes in the electric field at the same wavelength under different temperatures to explain the variations in absorption. Compared to previous work, our structure has only three layers in a single unit, making it easy to process and produce. Additionally, the absorption device's operating bandwidth and average absorption rate in the mid-infrared range have been significantly improved. Furthermore, the absorption device exhibits substantial incident angle tolerance and polarization insensitivity. We believe that this design has broad application potential in future optothermal conversion, infrared stealth, and thermal radiation.

Investigation of SAR reduction and gain enhancement using an all-textile antenna with metamaterial structure for wireless body area network applications

This work presents a wideband, low-profile, and flexible antenna that incorporates metamaterial (MTM) structures and textile materials. The antenna design is simulated using CST Microwave Studio, incorporating flexible textile elements such as a felt substrate and conductive fabric. The developed antenna's performance was examined numerically in free space and on a human body. The antenna with MTM technology operates in the ultra-wideband (UWB) with a bandwidth ranging from 3.86 to 13 GHz. It possesses a low profile with a thickness of 5.34 mm, making it suitable for applications in wireless body area networks (WBAN). Through the integration of metamaterial structures, the antenna's gain is enhanced, reaching 8.85 dBi compared to the initial gain of 5.34 dBi. Notably, the gain consistently exceeds 6 dBi across the entire UWB range, indicating focused power in a specific direction. For applications on the human body, specific absorption rate (SAR) values were calculated and found to be well within safety limits defined by European standards. This ensures minimal back radiation when the antenna is worn on the body, enhancing signal transmission range in WBAN applications.

Compact ACS-fed MIMO antenna with dual-band notch characteristics for UWB applications

Abstract An ultra-wideband (UWB) and compact-size four-port multiple input multiple output (MIMO) antenna with a footprint of 34 mm × 34 mm fed by an asymmetric coplanar strip (ACS) is investigated. The proposed antenna is composed of four orthogonally placed identical modified elliptical-shaped radiators and achieves an impedance bandwidth of 3.4–12.2 GHz. By etching two inverted L-shaped slots in the radiator element, WLAN band and X-band are rejected in the operating communication range. Because of the usage of a meander line decoupler, the isolation enhancement at the 8–12 GHz band is achieved and the isolation is more than 18 dB for most of the UWB range. The performance of the proposed antenna is studied in terms of isolation between each port, radiation pattern, current distribution, gain, envelope correlation coefficient, diversity gain, and total active reflection coefficient. The compact size and reduced complexity make the proposed design highly suitable for portable devices.

Transparent ultrawideband polarization-insensitive absorber with optimal thickness based on a grid ITO structure

With the large-scale commercialization of broadband wireless communication technologies, interference between spatial electromagnetic waves (EMWs) is becoming increasingly serious. As devices for solving electromagnetic interference (EMI) problems, microwave absorbers (MAs) have become increasingly mature with the rapid development of artificial electromagnetic structures. However, current MAs still face challenges in terms of wideband absorption, wide-angle absorption, thickness, etc., which limits their application scenarios. Therefore, this paper proposes a transparent ultrawideband polarization-insensitive absorber based on a grid indium tin oxide (ITO) structure. This design adopts a multilayer structure with a total thickness of 3.525 mm (0.114λ L ), close to the predicted minimum thickness, to expand the bandwidth. The grid-patterned ITO film resonant structure and ITO film ground plane are designed to further improve optical transmittance by increasing duty ratios. Simulation results demonstrate over 90% absorption from 9.7 GHz to 69.2 GHz, with a fractional bandwidth (FBW) of 150.8%. The absorber has good incident angle stability and polarization insensitivity. When the incident angle varies within 0-60°, the proposed absorber maintains an absorption close to 80% over an ultrawideband range, and the absorption remains nearly constant when the polarization angle changes from 0° to 90°. The fabricated sample shows a visible light transmittance of approximately 73.2%, and shows an absorption performance consistent with simulations in the 6-38 GHz frequency range, validating the effectiveness of the proposed design. Due to its transparent, ultrawideband absorption, wide incident angle stability and polarization insensitivity properties, this proposed absorber has important guiding significance for applications in high-frequency transparent electronics, radars, communications systems and other devices working in the microwave frequency band.

Resilient Simultaneous Localization and Mapping Fusing Ultra Wide Band Range Measurements and Visual Odometry

In this paper we consider a Simultaneous Localization and Mapping (SLAM) problem for a moving agent using Visual Odometry (VO) while measuring the range from a set of Ultra Wide Band (UWB) antennas, deployed in unknown position in the environment. The solution approach is based on a switching observer which, under standard working conditions, for each observed UWB, uses a two dimensional Extended Kalman Filter (EKF) providing an estimate of the range and bearing of the observed UWB with respect to the agent. This information is then used in a Robust EKF algorithm which solves the SLAM problem with performances that, even before closing the loop, are comparable to the ones that a VO algorithm (namely ORB-SLAM2) would obtain only after closing the loop. Moreover, a resilient module is added to the algorithm to evaluate the reliability of the position estimate of each observed UWB. When the Visual Odometry is not available, the switching observer uses an auxiliary EKF to provide an estimate of the agent position. This makes the proposed approach robust with respect to several kinds of unmodeled disturbances, like multipath effects, and automatically adapts to sensor failures with resilience (e.g. when Visual Odometry or UWB measurements are not available).