Filtry
wszystkich: 640
wybranych: 580
Wyniki wyszukiwania dla: TERAHERTZ ANTENNAS
-
Generation-recombination and 1/f noise in carbon nanotube networks
PublikacjaThe low-frequency noise is of special interest for carbon nanotubes devices, which are building blocks for a variety of sensors, including radio frequency and terahertz detectors. We studied noise in as-fabricated and aged carbon nanotube networks (CNNs) field-effect transistors. Contrary to the majority of previous publications, as-fabricated devices demonstrated the superposition of generation-recombination (GR) and 1/f noise...
-
Noise Analysis of Continuous GPS Time Series of Selected EPN Stations to Investigate Variations in Stability of Monument Types
PublikacjaThe type of monument that a GPS antenna is placed on plays a significant role in noise estimation for each permanent GPS station. In this research 18 Polish permanent GPS stations that belong to the EPN (EUREF Permanent Network) were analyzed using Maximum Likelihood Estimation (MLE). The antennae of Polish EPN stations are placed on roofs of buildings or on concrete pillars. The analyzed data covers a period of 5 years from 2008...
-
Expedited Yield-Driven Design of High-Frequency Structures by Kriging Surrogates in Confined Domains
PublikacjaUncertainty quantification is an important aspect of engineering design, also pertaining to the development and performance evaluation of high-frequency structures systems. Manufacturing tolerances as well as other types of uncertainties, related to material parameters (e.g., substrate permittivity) or operating conditions (e.g., bending) may affect the characteristics of antennas or microwave devices. For example, in the case...
-
Selected properties and parameters of radio channel impulse response estimation in ISM 2.4 GHz band
PublikacjaThe article presents experimental research indicating that the impulse response of the communication channel, determined in practice, are not of an universal character, but only represent its approximate value for the frequency on which this measurement was made. Phases for each of the replicas of the measurement signal were determined during the analysis of the received signals in the baseband. Phase changes of individual replicas...
-
The supramolecular organization of self-assembling chlorosomal bacteriochlorophyll c, d, or e mimics
PublikacjaBacteriochlorophylls (BChls) c, d, and e are the main light-harvesting pigments of green photosynthetic bacteria that self-assemble into nanostructures within the chlorosomes forming the most efficient antennas of photosynthetic organisms. All previous models of the chlorosomal antennae, which are quite controversially discussed because no single crystals could be grown so far from these organelles, involve a strong hydrogen-bonding...
-
Measurement and Analysis of the Radio Wave Polarisation in Off-Body Communications in Indoor Environment
PublikacjaThe paper describes an analysis of the radio wave polarisation in off-body communications in indoor environment. The measurement stand for polarisation measurements has been shortly described. Five investigated scenarios with different body postures and different antenna placements have been characterize. The vertical and horizontal components of received radio signal have been analysed. The measure used in analysis is a ratio...
-
3D Metamaterial Ultra-Wideband Absorber for curved surface
PublikacjaThis paper proposes a three-dimensional metamaterial absorber based on a resistive film patch array to develop a low-cost, lightweight absorber for curved surfaces. An excellent absorption over a large frequency band is achieved through two different yet controllable mechanisms; In the first mechanism, a considerable attenuation in the wave power is achieved via graphite resistive films. The absorption is then intensified through...
-
Correction of determined coordinates of railway tracks in mobile satellite measurements
PublikacjaThis article examines one of the basic issues related to the technique of mobile satellite measurements in railway tracks. This problem concerns the correction of the determined coordinates of the track centerline. The need to perform this operation results from the GNSS receivers positioning at a certain height above the level of the existing track axis, leading to longitudinal and lateral shifts of antennas. The key problem here...
-
Impact of radio wave polarisation on off-body communications in indoor environments
PublikacjaThis paper describes the measurements and the analysis of the impact of radio wave polarisation on off-body communications in Body Area Networks in indoor environments. Measurements on polarisation impact are briefly described. Five investigated scenarios with different body postures and different antenna placements are characterised. The difference between the vertical and horizontal components of the received radio signal are...
-
Ochrona odbiorników GNSS przed zakłóceniami celowymi
PublikacjaArtykuł dotyczy zastosowania algorytmów przestrzennego cyfrowego przetwarzania sygnałów dla potrzeb selektywnej eliminacji sygnałów zakłócających pracę odbiorników nawigacji satelitarnej GNSS. Omówiono podatność tych odbiorników na ataki elektroniczne typu zagłuszanie oraz spoofing. Polegają one na celowej emisji sygnałów niepożądanych w paśmie pracy systemu. Następnie przedstawiono koncepcję przeciwdziałania tego rodzaju zakłóceniom...
-
A Cross-Polarisation Discrimination Analysis of Off-Body Channels in Passenger Ferryboat Environments
PublikacjaThere is a need for investigating radio channels for Body Area Networks considering the depolarisation phenomenon and new types of environments, since these aspects are becoming very important for systems design and deployment. This paper presents an analysis of cross-polarisation discrimination for off-body channels based on a measurement campaign performed in a passenger ferryboat, i.e., where all walls, floors and ceilings are...
-
System wykrywania i przeciwdziałania spoofingowi GPS
PublikacjaSpoofing w systemach nawigacji satelitarnej jest atakiem elektronicznym, który polega na nieuprawnionej emisji sygnałów stanowiących imitacje rzeczywistych sygnałów odbieranych z satelitów. Powoduje on wyznaczenie nieprawidłowych informacji o czasie, położeniu i prędkości odbiornika. Z uwagi na trudność jego wykrycia, spoofing stanowi poważniejsze zagrożenie niż proste zagłuszanie sygnałów zakłóceniem o dużej mocy (ang. jamming)....
-
Acceleration of the DGF-FDTD method on GPU using the CUDA technology
PublikacjaWe present a parallel implementation of the discrete Green's function formulation of the finite-difference time-domain (DGF-FDTD) method on a graphics processing unit (GPU). The compute unified device architecture (CUDA) parallel computing platform is applied in the developed implementation. For the sake of example, arrays of Yagi-Uda antennas were simulated with the use of DGF-FDTD on GPU. The efficiency of parallel computations...
-
Wideband Radio Direction Finder Implemented in Software Defined Radio Technology
PublikacjaIn the paper a wideband radio direction finder (RDF) implemented in software defined radio (SDR) technology and the results of hardware layer research, including developed antenna switching unit (ASU), are presented. The results of tests of the devices, which are the part of the software defined radio platform (SDRP), and antenna switching unit, confirmed the possibility of using selected components in the final solution.
-
Hybridization of the FDTD method with use of the discrete Green's function
PublikacjaIn this contribution, a hybrid technique is presented which combines the finite-difference time-domain (FDTD) method and the discrete Green's function (DGF) formulation of this method. FDTD is a powerful technique for the analysis of complex penetrable objects but its application is not efficient when the computational domain includes many free-space cells. Therefore, the hybrid method was developed which is applicable to complex...
-
Bayesian Optimization for solving high-frequency passive component design problems
PublikacjaIn this paper, the performance of the Bayesian Optimization (BO) technique applied to various problems of microwave engineering is studied. Bayesian optimization is a novel, non-deterministic, global optimization scheme that uses machine learning to solve complex optimization problems. However, each new optimization scheme needs to be evaluated to find its best application niche, as there is no universal technique that suits all...
-
A Method for Determination and Compensation of a Cant Influence in a Track Centerline Identification Using GNSS Methods and Inertial Measurement
PublikacjaAt present, the problem of rail routes reconstruction in a global reference system is increasingly important. This issue is called Absolute Track Geometry, and its essence is the determination of the axis of railway tracks in the form of Cartesian coordinates of a global or local coordinate system. To obtain such a representation of the track centerline, the measurement methods are developed in many countries mostly by the using...
-
On the approximation of the UWB dipole elliptical arms with stepped-edge polygon
PublikacjaA simple method of approximation of the ellipticalpatch with stepped-edge polygon is proposed as an introductionto wider studies over the planar ultrawideband (UWB) antennas.The general idea is to replace the elliptical patch with an equivalentpolygonal patch, with minimum loss in the performance. Theprinciples of the proposed method are presented in this letter, aswell as the results of performed numerical studies and its experimentalverification....
-
A low-voltage CMOS negative impedance converter for analogue filtering applications
PublikacjaLow-voltage high-frequency continuous-time filters are still required in many applications and are the subject of continuing research. There are many techniques to realize integrated filters, including OTA C, Opamp RC and MOSFET-C-Opamp. The latter two show high dynamic range at low supply voltage, but their frequency operating range is usually limited to several megahertz. Transconductance filters are dedicated to higher frequencies....
-
On Improved-Reliability Design Optimization of High-Frequency Structures Using Local Search Algorithms
PublikacjaThe role of numerical optimization has been continuously growing in the design of high-frequency structures, including microwave and antenna components. At the same time, accurate evaluation of electrical characteristics necessitates full-wave electromagnetic (EM) analysis, which is CPU intensive, especially for complex systems. As rigorous optimization routines involve repetitive EM simulations, the associated cost may be significant....
-
Vehicular Communication Environments
PublikacjaCommunication to and between road vehicles (cars, truck, buses, trains, etc.) are of growing interest. This is partly due to the attractive services that cooperative intelligent transport systems (C-ITSs) provides, mainly in the areas of traffic safety and traffic efficiency. An enabler for C-ITS is wireless vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication, collectively referred to as vehicle-to-X (V2X)...
-
Measurements of Path Loss in Off-Body Channels in Indoor Environments
PublikacjaThe main goal of the paper is to investigate the influence of body orientation and on-body antenna placement on the path loss in off-body communications. In addition, the influence of different bodies is analysed.
-
Path Loss Analysis in Off-Body Channels in Indoor Environment
PublikacjaThis temporary document describes an analysis of path loss in off-body channels in an indoor environment. The influence of body orientation and on-body antenna placement on path loss in off-body communications as well as of different bodies has been investigated. Five static scenarios, six distances between body and antenna and eight body orientations were analysed; moreover, two dynamic scenarios were investigated. The smallest...
-
Design and experimental verification of multi-layer waveguide using pin/hole structure
PublikacjaThis study presents a novel technique for minimizing RF leakage in metallic hollow waveguides fabricated using the multilayer split-block method. By integrating a pin/hole wall into the split-block multilayers, a substantial reduction of RF leakage can be achieved while reducing the circuit size and mitigating the performance variations. To validate the proposed approach, a slot antenna fed by single ridge waveguide has been prototyped...
-
Pomiarowa ocena efektywności systemu antyspoofingowego opartego na przetwarzaniu wieloantenowym
PublikacjaNiniejszy referat dotyczy problemu wykrywania i przeciwdziałania atakom typu spoofing w globalnych systemach nawigacji satelitarnej. Pierwsza część referatu stanowi wprowadzenie w temat spoofingu oraz przegląd sposobów jemu przeciwdziałania. Następnie, przedstawiono autorską koncepcję systemu antyspoofingowego opartego na przetwarzaniu wieloantenowym, a także opisano implementację prototypu tego systemu. Część trzecią poświęcono...
-
[Komentarz do artykułu] Yin, W.-Y., Wu, B., Miao, M., Doi, L.B., Li, L.-W., and Kooi, P.-S.: Experimental characterisation and modelling of on-chip capacitors and resistors on GaAs substrates.
PublikacjaDokonano krytycznej oceny wartości elementów schematu zastępczego rezystorów monolitycznych wykonanych na podłożu GaAs przedstawionych w pracy: Yin, W.-Y., Wu, B., Miao, M., Doi, L.B., Li, L.-W., and Kooi, P.-S.: Experimental characterisation and modelling of on-chip capacitors and resistors on GaAs substrates, IEE Proc. Microw. Antennas and Propag., 2002,149, (1), pp.50-52.
-
System Loss in UWB Off-Body Communications in a Ferry Environment
PublikacjaIn this paper, the system loss in UWB off-body communications in a ferry environment based on measurements is presented. A mobile measurement set-up, consisting of WBAN nodes with UWB DWM1000 modules, was used. System loss was split into LOS and NLOS conditions. For the former, the smallest mean value, 24.4 dB, was obtained for the user approaching the fixed terminal, with the antenna on his chest, and the largest, 28.1 dB, for...
-
Recent advances in high-frequency modeling by means of domain confinement and nested kriging
PublikacjaDevelopment of modern high-frequency components and circuits is heavily based on full-wave electromagnetic (EM) simulation tools. Some phenomena, although important from the point of view of the system performance, e.g., EM cross-coupling effects, feed radiation in antenna arrays, substrate anisotropy, cannot be adequately accounted for using simpler means such as equivalent network representations. Consequently, the involvement...
-
Recent Advances in Accelerated Multi-Objective Design of High-Frequency Structures using Knowledge-Based Constrained Modeling Approach
PublikacjaDesign automation, including reliable optimization of engineering systems, is of paramount importance for both academia and industry. This includes the design of high-frequency structures (antennas, microwave circuits, integrated photonic components), where the appropriate adjustment of geometry and material parameters is crucial to meet stringent performance requirements dictated by practical applications. Realistic design has...
-
Response Feature Technology for High-Frequency Electronics. Optimization, Modeling, and Design Automation
PublikacjaThis book discusses response feature technology and its applications to modeling, optimization, and computer-aided design of high-frequency structures including antenna and microwave components. By exploring the specific structure of the system outputs, feature-based approaches facilitate simulation-driven design procedures, both in terms of improving their computational efficiency and reliability. These benefits are associated...
-
Time domain model of the resonance-based electromagnetic pulses emission system
PublikacjaIn the literature, the emission properties of the electromagnetic field pulse systems based on high voltage antennas (HVR) have been widely described. In order to increase the emission efficiency by extending duration and increasing amplitude of the impulse it is possible to use a resonance system tuned to the parameters of the signal shaped in the pulse forming circuit. The synthesis of a time-domain simulation model of a complex...
-
Editorial for the special issue on advances in forward and inverse surrogate modeling for high-frequency design
PublikacjaThe design of modern‐day high‐frequency devices and circuits, including microwave/RF, antenna and photonic components, historically has relied on full‐wave electromagnetic (EM) simulation tools. Initially used for design verification, EM simulations are nowadays used in the design process itself, for example, for finding optimum values of geometry and/or material parameters of the structures of interest. In a growing number of...
-
Implementation of DIFAR Processing in ASW Dipping Sonar
PublikacjaThis paper presents the implementation of the signal processing algorithm used by buoy DIFAR (Directional Frequency Analysis and Recording), that is fully operational on Polish Navy anti-submarine warfare (ASW) helicopters and ships, applied to dipping sonars for detection and tracking of submarines. The development of the DSP algorithms was a part of the modernization of sonars conducted at the Gdansk University of Technology....
-
Local response surface approximations and variable-fidelity electromagnetic simulations for computationally efficient microwave design optimisation
PublikacjaIn this study, the authors propose a robust and computationally efficient algorithm for simulation-driven design optimisation of microwave structures. Our technique exploits variable-fidelity electromagnetic models of the structure under consideration. The low-fidelity model is optimised using its local response surface approximation surrogates. The high-fidelity model is refined by space mapping with polynomial interpolation of...
-
Wideband Channel Measurements for Polarised Indoor Off-Body Communications
PublikacjaThis paper presents the initial results of wideband channel measurements for polarised off-body communication at 5.8 GHz, in an indoor environment. Channel Impulse Response measurements were performed simultaneously for two orthogonal polarisations of the wearable antenna, and repeated for vertical and horizontal orientations of the off-body one. Four types of measurement scenarios were considered in order to investigate the influence...
-
An Empirical System Loss Model for Body Area Networks in a Passenger Ferry Environment
PublikacjaThis paper presents a general empirical system loss model for estimating propagation loss in Body Area Networks in off-body communications at 2.45 GHz in a passenger ferry environment. The model is based on measurements, which were carried out in dynamic scenarios in the discotheque passenger ferry environment. The model consists of three components: mean system loss, attenuation resulting from the variable antenna position on...
-
An Empirical System Loss Model for Body Area Networks in a Passenger Ferry Environment
PublikacjaThis paper presents a general empirical system loss model for estimating propagation loss in Body Area Networks in off-body communications at 2.45 GHz in a passenger ferry environment. The model is based on measurements, which were carried out in dynamic scenarios in the discotheque passenger ferry environment. The model consists of three components: mean system loss, attenuation resulting from the variable antenna position on...
-
A New Expression for the 3-D Dyadic FDTD-Compatible Green's Function Based on Multidimensional Z-Transform
PublikacjaIn this letter, a new analytic expression for the time-domain discrete Green's function (DGF) is derived for the 3-D finite-difference time-domain (FDTD) grid. The derivation employs the multidimensional Z-transform and the impulse response of the discretized scalar wave equation (i.e., scalar DGF). The derived DGF expression involves elementary functions only and requires the implementation of a single function in the multiple-precision...
-
A Low-Profile Metal-backed Dipole Loaded with Closely Coupled Arc-shaped Open Stubs for On-metal Tag Design with Wide Frequency Tuning Capability
PublikacjaThis research has presented a single-layer metal-backed dipole antenna, which consists of a feedline loaded with two pairs of closely-coupled arc-shaped open stubs, for designing a metal-mountable tag that features tuning capability over a wide range of frequency. Here, the stubs can generate sufficient inductive reactance for bringing down the tag resonant frequency tunable in both the regulated UHF RFID passbands (North American...
-
Investigation of the impact of ITRF2014/IGS14 on the positions of the reference stations in Europe
PublikacjaIn January 2017, the new realization of the International Terrestrial Reference Frame (ITRF) – ITRF2014, was released. Besides the higher accuracy and consistency of the new frame, an entirely new element – the post seismic deformation - was included. Moreover, the definition of the fundamental points has also been changed. All changes related to the new reference frame haveconsequences in the precise positioning using GNSS observations....
-
Coplanar Waveguide-Fed Broadband Microwave Devices with (or without) a Thin Dielectric Substrate for Use in Flexible Electronic Systems
PublikacjaTwo examples of microwave devices, fed by a coplanar waveguide and realized on a thin substrate (or without such a substrate), are employed to investigate the influence of devices’ curvatures and the proximity of different materials on their parameters. To perform the tests, a broadband antenna and a low-pass filter are chosen. A feeding coplanar waveguide is realized on a dielectric material brick attached to an SMA connector...
-
Selected acoustic images of the Gdansk Bay
PublikacjaThe main goal of the paper is to describe the results of sounding the Gdansk Bay seabed by using a parametric sub-bottom profiler, multibeam echosounder and side scan sonar. Quality of dsata obtained during trials depends interalia on a proper location of antenna to reduce influence of pitch, roll and heave motions as well as ship noise.
-
A new hybrid method for analysis of scattering from arbitrary configuration of cylindrical objects
PublikacjaArtykuł opisuje nową hybrydową metodę analizy rozpraszania fali elektromagnetycznej od obiektów cylindrycznych o dowolnym przekroju poprzecznym. W prezentowanym podejściu każdy obiekt jest traktowany jako efektywny cylinder o przekroju kołowym, opisany przez macierz impedancyjną. W celu uzyskania owej macierzy zastosowano połączenie metod różnic skończonych w dziedzinie częstotliwości (FDFD) i dopasowania rodzajów (MM). W celu...
-
Analysis and design of a polarizer rotator system
PublikacjaW artykule przedstawiono metodę analizy wielosekcyjnego polaryzatora złożonego z periodycznych szyków obiektów cylindrycznych. W celu analizy badanej struktury zastosowano metodę pełnofalową opartą na metodzie dopasowania rodzajów. Opracowany algorytm został zweryfikowany poprzez porównanie uzyskanych wyników z wynikami otrzymanymi z przybliżonego modelu transmisyjnego oraz z własnymi pomiarami wykonanego prototypu.
-
Analysis of scattering from arbitrary configuration of elliptical obstacles using T-matrix representation
PublikacjaW artykule przedstawiono nową metodę analizy zjawiska rozpraszania dla dowolnej konfiguracji obiektów eliptycznych. Przedstawione podejście, dotyczącego pojedynczego obiektu, oparte jest na połączeniu analizy w układzie eliptycznym i cylindrycznym. W analizie wielu obiektów wykorzystana została procedura iteracyjna. Uzyskane wyniki zostały zweryfikowane przy wykorzystaniu oprogramowania komercyjnego.
-
Periodicity Matters: Grating or lattice resonances in the scattering by sparse arrays of subwavelength strips and wires.
Publikacja -
Calculation of the propagation loss in urban radio-access systems
PublikacjaZweryfikowano eksperymentalnie modele propagacyjne opracowane dla telefonii komórkowej w mieście, stosowane przy analizach projektowych systemów dostępowych. Przeprowadzono obszerne badania pomiarowe i zebrano prawie 19 tys. pomiarów. Na tej podstawie, stosując wielowymiarową analize regresji oraz zaproponowaną charakterystykę propagacyjną radiowych łączy dostępowych, opracowano nowy wielowariantowy model propagacyjny przeznaczony...
-
Resonance Frequency Calculation of a Multilayer and Multipatch Spherical Microstrip Structure Using a Hybrid Technique
PublikacjaThis communication offers a rigorous analysis of the resonance frequency problem of a spherical microstrip structure mounted on a multilayer, dielectric-coated metallic sphere, with an electrically small radius. The structure consists of single or multiple metallic patches with arbitrary shapes. A full-wave analysis is employed with the use of proposed hybrid approach, combining the finite-difference technique with a spectral domain...
-
Rapid multi-objective design optimisation of compact microwave couplers by means of physics-based surrogates
PublikacjaThe authors introduce a methodology for fast multi-objective design optimisation of miniaturised microwave couplers. The approach exploits the surrogate-based optimisation paradigm with an underlying low-fidelity model constructed from an equivalent circuit of the structure under consideration, corrected through implicit and frequency space mapping. A fast prediction tool obtained this way is subsequently optimised by a multi-objective...
-
Rapid simulation-driven design of miniaturised dual-band microwave couplers by means of adaptive response scaling
PublikacjaOne of the major challenges in the design of compact microwave structures is the necessity of simultaneous handling of several objectives and the fact that expensive electromagnetic (EM) analysis is required for their reliable evaluation. Design of multi-band circuits where performance requirements are to be satisfied for several frequencies at the same time is even more difficult. In this work, a computationally efficient design...