Filtry
wszystkich: 821
wybranych: 619
Wyniki wyszukiwania dla: PROBES , BANDWIDTH , COHERENCE , CORRELATION , FREQUENCY MEASUREMENT , TRANSFER FUNCTIONS , BASEBAND
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Rapid Re-Design and Bandwidth/Size Trade-Offs for Compact Wideband Circular Polarization Antennas Using Inverse Surrogates and Fast EM-Based Parameter Tuning
PublikacjaDesign of compact wideband circularly polarized (CP) antennas is challenging due to the necessity of simultaneous handling of several characteristics (reflection, axial ratio, gain) while maintaining a small size of the structure. Antenna re-design for various operating bands is clearly more difficult yet practically important because intentional reduction of the bandwidth (e.g., by moving the lower edge of the operating band up...
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Novel fast non-linear electrochemical impedance method for corrosion investigations
PublikacjaThe paper presents a novel approach to corrosion rate monitoring using non-linear electrochemical impedance spectroscopy. The authors propose a new variant of non-linear impedance measurement using amplitude-modulated multi-frequency ac perturbation signal. It allows shortening of measurement duration so it is possible to monitor corrosion rate of the systems experiencing rapid changes. In this way a limitation resulting from lack...
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Experimental investigations on heat transfer enhancement in shell coil heat exchanger with VARIABLE Baffles GEOMETRY
PublikacjaThe paper presents the possibility of using passive intensification of heat transfer in the form of baffles to increase the energy efficiency of the shell and coil heat exchanger. The experiment was carried out by using a modular coil heat exchanger in the form of an electric heater. Water was used as a working fluid with constant thermal-flow parameters at the inlet of the module. It should be noted that experiments were made...
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Testing the impact of simplifications adopted in models describing wave loads on ship
PublikacjaThe wave-ship system in naval architecture is generally assumed to be a linear one. This allows for the computation of a transfer function of ship response to waves including wave loads on ship. The transfer function and the wave spectral density function enable the development of the stochastic process of wave loads on ship, corresponding to the irregular wave generating that loads. If the mathematical models of wave load transfer...
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Testing the impact of simplifications adopted in models describing wave loads on ship
PublikacjaThe wave-ship system in naval architecture is generally assumed to be a linear one. This allows for the computation of a transfer function of ship response to waves including wave loads on ship. The transfer function and the wave spectral density function enable the development of the stochastic process of wave loads on ship, corresponding to the irregular wave generating that loads. If the mathematical models of wave load transfer...
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High gain/bandwidth off‑chip antenna loaded with metamaterial unit‑cell impedance matching circuit for sub‑terahertz near‑field electronic systems
PublikacjaAn innovative off-chip antenna (OCA) is presented that exhibits high gain and efficiency performance at the terahertz (THz) band and has a wide operational bandwidth. The proposed OCA is implemented on stacked silicon layers and consists of an open circuit meandering line. It is shown that by loading the antenna with an array of subwavelength circular dielectric slots and terminating it with a metamaterial unit cell, its impedance...
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Structural optimization of microjet array cooling system
PublikacjaThe single phase heat transfer from an upward facing, horizontal copper surface to arrays of impinging water jets was experimentally investigated. Experimental configuration allows for a free-surface unconfined jets flow. Square nozzles 50 × 100 μm arranged in four different geometries were used. Additionally, for the set of two jets array geometry was varied by adjusting the nozzle to nozzle distance. The area averaged heat transfer...
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The evaluation of the vibration measurement usability of electronic indicator lemag "premet C"
PublikacjaThe measuring possibilities of modern compression and combustion pressure analyzers are extended with additional functions. One of them is parallel to the pressure measurement, the measurement of vibrations in the region of the cylinder head. The paper presents a general assessment of the vibration measurement function of the electronic indicator LEMAG "PREMET C". This feature is very rarely offered by manufacturers of these devices....
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SPECTRAL DYNAMIC ANALYSIS OF A STATIONARY JACK-UP PLATFORM
PublikacjaThe paper refers to the dynamic short-term response analysis of the Baltic steel drilling platform (see Fig.2) in a random sea-state represented by one-dimensional wave spectrum proposed by Striekalov and Massel and it is recommended for the Baltic Sea area. The Baltic drilling platform is a jack-up type platform for the exploration and exploitation of oil under the Baltic Sea. The analysis presented deals with the stationary...
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Novel structure and design of enhanced-bandwidth hybrid quadrature patch coupler
PublikacjaA novel structure and design optimization procedure of an enhanced-bandwidth hybrid quadrature patch coupler is proposed. Improved performance of the circuit has been obtained by parameterizing the coupler sections using splines, which introduces additional degrees of freedom. Due to computational complexity of the parameter adjustment problem, a sequential design procedure is applied. In each iteration, a selected number of spline...
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Metamaterial-Based Series-Fed Antenna with High Gain and Wideband Performance for Millimeter Wave Spectrum Applications
PublikacjaThis paper presents a high-gain, wideband series-fed antenna designed for 5G millimeter-wave (MMW) applications. The structure employs a substrate-integrated waveguide (SIW)-based power splitter and metamaterials (MMs). The power divider functions effectively at 27.5 GHz, exhibiting an impedance bandwidth from 26.9–28.6 GHz. The series-fed dipole is assembled on the SIW-based power splitter, incorporating four dipoles with varying...
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Measurements of relative frequency instability
PublikacjaFrequency constancy can be determined by the change in time for the subsequent periods. The article shows that classical the method of digital period measurement is not suitable for the measurement process. Therefore, a method using an integrating circuit is being proposed. Errors in the measurement of the given method have been analyzed.
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Synthesis of coupled lossy resonator filters.
PublikacjaA technique for fast synthesis of coupling matrix low-pass prototypes of generalized. Chebyshev bandpass filters with lossy resonators is presented in this letter. The coupling matrix is found by solving a nonlinear least squares problem based on zeros and poles of filter's transfer functions.
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New approach to noncausal identification of nonstationary stochastic systems subject to both smooth and abrupt parameter changes
PublikacjaIn this paper we consider the problem of finiteintervalparameter smoothing for a class of nonstationary linearstochastic systems subject to both smooth and abrupt parameterchanges. The proposed parallel estimation scheme combines theestimates yielded by several exponentially weighted basis functionalgorithms. The resulting smoother automatically adjustsits smoothing bandwidth to the type and rate of nonstationarityof the identified...
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Niskokoherencyjne czujniki światłowodowe wykorzystujące cienkowarstwowe struktury nanodiamentowe
PublikacjaZnaczny rozwój technologii wytwarzania czujników światłowodowych spowodował, że są one powszechnie dostępne i stosowane w wielu gałęziach przemysłu, nauki oraz medycyny. Zastosowanie nowych materiałów w konstrukcji takich czujników niesie za sobą duży potencjał. Celem rozprawy jest przedstawienie możliwości wykorzystania cienkowarstwowych struktur nanodiamentowych w niskokoherencyjnych czujnikach światłowodowych, które poprawią...
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Wideband High-Gain Low-Profile Series-Fed Antenna Integrated with Optimized Metamaterials for 5G millimeter Wave Applications
PublikacjaThis paper presents a series-fed four-dipole antenna with a broad bandwidth, high gain, and compact size for 5G millimeter wave (mm-wave) applications. The single dipole antenna provides a maximum gain of 6.2 dBi within its operational bandwidth, which ranges from 25.2 to 32.8 GHz. The proposed approach to enhance both gain and bandwidth involves a series-fed antenna design. It comprises four dipoles with varying lengths, and a...
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Measurements of Dispersed Phase Velocity in Two-Phase Flows in Pipelines Using Gamma-Absorption Technique and Phase of the Cross-Spectral Density Function
PublikacjaThis paper concerns the application of the gamma radiation absorption method in the measurements of dispersed phase velocity in two-phase flows: liquid–gas flow in a horizontal pipe- line and liquid–solid particles in a vertical pipe. Radiometric sets containing two linear 241Am gamma radiation sources and two NaI(Tl) scintillation detectors were used in the research. Due to the stochastic nature of the signals obtained from the...
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An Instantaneous Engine Speed Estimation Method Using Multiple Matching Synchrosqueezing Transform
PublikacjaInstantaneous rotational speed measurement of the engine is crucial in routine inspection and maintenance of an automobile engine. Since the contact measurement of rotational speed is not always available, the vibration measurement has been used for noncontact rotational speed estimation methods. Unfortunately, the accuracy of the noncontact estimation methods by analyzing engine vibration frequency is not satisfactory due to the...
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Novel structure and size-reduction-oriented design of microstrip compact rat-race coupler
PublikacjaIn this paper, a novel structure of a miniaturized microstrip rat-race coupler has been proposed. Surrogate-based optimization procedures are applied to explicitly reduce the coupler size while maintaining equal power split at the operating frequency of 1 GHz and sufficient bandwidth for return loss and isolation characteristics. The optimization is performed using the objective function with four penalty components. The footprint...
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Detection system for optical coherence tomography: Czerny-Turner spectrometer
PublikacjaResearch methods based on spectral analysis have powerful impact on development in many field of science. Signal spectrum can be a source of useful and important data. It enables to obtain information about physical and chemical properties of tested materials. This paper has been devoted to describe optical design for high resolution spectrometer, which is significant element of optical coherence tomography (OCT) systems. Designed...
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Applicability of arrays of microjets heat transfer correlations to design compact heat exchangers
PublikacjaThe article presents experimental studies on a compact heat exchanger with heat transfer intensification by means of impinging microjets. The pursuit to provide high performance of heat exchangers is a response to the demand both in economics and in the universal tendency to miniaturization of industrial equipment. This paper presents the design and tests of a prototype, microjet heat exchanger. The modular design of the heat exchanger...
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Efficient signal processing in spectroscopic optical coherence tomography
PublikacjaSpectroscopic optical coherence tomography (SOCT) is an extension of a standard OCT technique, which allows to obtain depth-resolved, spectroscopic information on the examined sample. It can be used as a source of additional contrast in OCT images e.g. by encoding certain features of the light spectrum into the hue of the image pixels. However, SOCT require computation of time-frequency distributions of each OCT A-scan, what is...
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Text Categorization Improvement via User Interaction
PublikacjaIn this paper, we propose an approach to improvement of text categorization using interaction with the user. The quality of categorization has been defined in terms of a distribution of objects related to the classes and projected on the self-organizing maps. For the experiments, we use the articles and categories from the subset of Simple Wikipedia. We test three different approaches for text representation. As a baseline we use...
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Thermodynamic and geometrical characteristics of mixed convection heat transfer in the shell and coil tube heat exchanger with baffles
PublikacjaThe article presents passive heat transfer enhancement method in the form of baffles to increase the energy efficiency of the shell coil heat exchanger. Conducted literature review shows that, despite numer- ous studies, there is little work on the intensification of heat transfer at the shell side. Most of the work focuses on the impact of geometrical parameters of the coil itself. This article successfully proves that it is possible...
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Voltage Harmonics Transfer through Medium Voltage Instrument Transformers
PublikacjaVoltage transformers are widely used in power quality monitoring systems in medium and high voltage grids. This paper presents accuracy problems related to voltage harmonics transfer through instrument transformers. A simplified lumped-parameters wideband circuit model of the voltage transformer is proposed and verified by simulation and experimental investigations. A number of voltage transformers have been tested in the frequency...
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Voltage Transients Transfer over Medium Voltage Instrument Transformers
PublikacjaThis paper presents voltage harmonic transfer accuracy problems through voltage transformers which are used in power quality monitoring systems in medium and high voltage grids. A simplified lumped parameters circuit model of the voltage transformer is proposed and verified by simulation and experimental investigations. A number voltage transformers typically used in medium voltage grid has been tested in the conducted disturbances...
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An Analysis of Elliptical-Rectangular Patch Structure on Multilayer Elliptic Cylinders
PublikacjaThe resonance frequency problem of an ellipticalrectangular patch mounted on multilayered dielectric coated elliptic conducting cylinder, is investigated in this paper. A fullwave analysis and a moment-method calculation are employed. The analysis is carried out considering the expansion of the field as a series of Mathieu functions. An additional theorem for Mathieu functions is utilized to investigate the non-confocal ellipse...
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Frequency Selective Surface Based MIMO Antenna Array for 5G Millimeter-Wave Applications
PublikacjaAbstract: In this paper a radiating element consisting of a modified circular patch is proposed for MIMO arrays for 5G millimeter-wave applications. The radiating elements in the proposed 2×2 MIMO antenna array are orthogonally configured relative to each other to mitigate mutual coupling that would otherwise degrade the performance of the MIMO system. The MIMO array was fabri-cated on Rogers RT/Duroid high frequency substrate...
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Rapid Evaluation of Poultry Meat Shelf Life Using PTR-MS
PublikacjaThe use of proton transfer reaction mass spectrometry (PTR-MS) for freshness classification of chicken and turkey meat samples was investigated. A number of volatile organic compounds (VOCs) were selected based on the correlation (> 95%) of their concentration during storage at 4 °C over a period of 5 days with the results of the microbial analysis. In order to verify if the selected compounds are not sample-specific, a number...
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Gold nanoparticles evaluation using functional optical coherence tomography
PublikacjaThe main object of this research was to assess the ability to characterize the gold nanoparticles using optical modalities like optical coherence tomography. Since the nanoparticles, especially gold one, have been very attractive for medical diagnosis and treatment the amount of research activities have been growing rapidly. The nanoparticles designed for different applications like contrast agents or drugs delivery change the...
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Low-coherence sensors with nanolayers for biomedical sensing
PublikacjaIn this paper, we describe the fiber optic low-coherence sensors using thin film. We investigated their metrological parameters. Presented sensors were made with the use of standard telecommunication single mode optical fiber (SMF28). Different materials were applied to obtain thick layers, such as boron doped diamond, silver and gold. The thickness of layers used in the experiments ranged from 100 nm to 300 nm. Measurements were...
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Novel Coplanar-Strip-Based Excitation Technique for Design of Broadband Circularly Polarization Antennas with Wide 3-dB Axial Ratio Beamwidth
PublikacjaIn this paper, a novel excitation technique for design of a single-point-fed compact low-profile wide-slot antennas with broadband circular polarization (CP) and wide 3 dB axial ratio (AR) beamwidth is presented. Two inverted L-shape parasitic strips placed coplanar to the microstrip line of an asymmetric CPW, and a horizontal strip that protrudes from the vertical edge of the backside ground plane of the substrate are used for...
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Application of ANN and PCA to two-phase flow evaluation using radioisotopes
PublikacjaIn the two-phase flow measurements a method involving the absorption of gamma radiation can be applied among others. Analysis of the signals from the scintillation probes can be used to determine the number of flow parameters and to recognize flow structure. Three types of flow regimes as plug, bubble, and transitional plug – bubble flows were considered in this work. The article shows how features of the signals in the time and...
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How Can We Identify Electrophysiological iEEG Activities Associated with Cognitive Functions?
PublikacjaElectrophysiological activities of the brain are engaged in its various functions and give rise to a wide spectrum of low and high frequency oscillations in the intracranial EEG (iEEG) signals, commonly known as the brain waves. The iEEG spectral activities are distributed across networks of cortical and subcortical areas arranged into hierarchical processing streams. It remains a major challenge to identify these activities in...
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ESTIMATION OF NONSTATIONARY HARMONIC SIGNALS AND ITS APPLICATION TO ACTIVE CONTROL OF MRI NOISE
PublikacjaA new adaptive comb filtering algorithm, capable of tracking the fundamental frequency and amplitudes of different frequency components of a nonstationary harmonic signal embedded in white measurement noise, is proposed. Frequency tracking characteristics of the new scheme are studied analytically, proving (under Gaussian assumptions and optimal tuning) its statistical efficiency for quasi-linear frequency changes. Laboratory tests...
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Signal conditioning for examination of shallow-water acoustic noise correlation properties
PublikacjaThe article describes the process of signal conditioning for examination of acoustic noise correlation properties in shallow water. Knowledge of these properties is very important for the design processes of passive and active hydroacoustic systems. This paper focuses on the above issue from the point of view of passive sonar. In sonar systems, signal processing algorithms operate on both useful acoustic signals, and accompanying...
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Optimal Multivariable Control for Modified Z-source Based IPT
PublikacjaThis paper describes Z-source based inductive power transfer topologies control approaches. The goal of this work is a multi-variable control approach which involves a constant voltage/constant current control along with an optimal frequency control to obtain maximum efficiency. This control is applied to the wireless power transfer system based on a modified Z-source topology. The description of the control method along with simulation...
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New Approach to Noncasual Identification of Nonstationary Stochastic FIR Systems Subject to Both Smooth and Abrupt Parameter Changes
PublikacjaIn this technical note, we consider the problem of finite-interval parameter smoothing for a class of nonstationary linear stochastic systems subject to both smooth and abrupt parameter changes. The proposed parallel estimation scheme combines the estimates yielded by several exponentially weighted basis function algorithms. The resulting smoother automatically adjusts its smoothing bandwidth to the type and rate of nonstationarity...
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The mediational role of future and past time perspectives in the relationship between negative affectivity and sense of coherence
PublikacjaSense of coherence (SoC) can promote positive coping, and one of its most prominent negative correlates is negative affectivity (NA). In the current study, we hypothesized that future and past time perspectives (TPs) will mediate the relationship between sense of coherence and negative affectivity, and the inverse relationship. The study was questionnaire-based, performed online. N = 719 participants aged 25-45 from...
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Generalization of Kramers-Krönig relations for evaluation of causality in power-law media
PublikacjaClassical Kramers-Krönig (K–K) relations connect real and imaginary parts of the frequency-domain response of a system. The K–K relations also hold between the logarithm of modulus and the argument of the response, e.g. between the attenuation and the phase shift of a solution to a wave-propagation problem. For square-integrable functions of frequency, the satisfaction of classical K–K relations implies causality in the time domain....
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Monitoring of odors emitted from stabilized dewatered sludge subjected to aging using proton transfer reaction–mass spectrometry
PublikacjaOne of the potential emission sources of odorous compounds from wastewater treatment plants is sludge processing. The odorous compounds released from dewatered sludge can result in odor nuisance. This study concerns the use of flux hood chamber combined with proton transfer reaction—time of flight—mass spectrometry (PTR-MS) technique for periodical monitoring of odorous compounds emitted from aged, stabilized dewatered sludge samples...
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Flicker Noise in Resistive Gas Sensors—Measurement Setups and Applications for Enhanced Gas Sensing
PublikacjaWe discuss the implementation challenges of gas sensing systems based on low-frequency noise measurements on chemoresistive sensors. Resistance fluctuations in various gas sensing materials, in a frequency range typically up to a few kHz, can enhance gas sensing by considering its intensity and the slope of power spectral density. The issues of low-frequency noise measurements in resistive gas sensors, specifically in two-dimensional...
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The forming and emission of high power electromagnetic pulses
PublikacjaAn impulse energy source, a power conditioning system and an electromagnetic field emitter are essential to generate an electromagnetic field pulse (EMFP) with a specific frequency bandwidth. Selected simulation results for a power conditioning system consisting of a fuse opening switch and a paraboloidal electromagnetic emitter have been presented in this article. The synthetic system examined in the simulation is powered by an...
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Rola nowego tramwaju wodnego w Gdańsku
PublikacjaStreszczenie Tramwaj wodny – środek miejskiej komunikacji zbiorowej czy jednostka przewozów turystyczny? Identyfikacja, zestawienie i analiza czynników transportu nowopowstałej usługi przewozowej z komunikacją miejską i przewozem turystycznym tj. :cennik biletów, sposobu dystrybucji biletów, czasu przejazdu dostępności, przebieg trasy i częstotliwości kursowania. Wskazanie funkcji przewozowej tramwaju wodnego w Gdańsku.
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On the synthesis of coupled-lossy resonator filters with unloaded quality factor control
PublikacjaA technique for fast synthesis of coupling matrix low-pass prototypes of generalized Chebyshev bandpass filters with lossy resonators is presented in this paper. The coupling matrix is found by solving a nonlinear least squares problem based on zeros and poles of filter's transfer functions. Additional constraints are introduced that allow one to control the level of unloaded quality factor of resonators.
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Cost-efficient design optimization of compact patch antennas with improved bandwidth
PublikacjaIn this letter, a surrogate-assisted optimization procedure for fast design of compact patch antennas with enhanced bandwidth is presented. The procedure aims at addressing a fundamental challenge of the design of antenna structures with complex topologies, which is simultaneous adjustment of numerous geometry parameters. The latter is necessary in order to find a truly optimum design and cannot be executed-at the level of high-fidelity...
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On the broadband behaviour of planar elliptical dipole-modal approach
PublikacjaBroadband behavior of planar elliptical dipole structure is analyzed using Illuminatin Modes (IM) approach. The current on patch has been expanded in series of eigenfunctions in form of Mathieu radial and angular functions. The frequency behavior of current distributions and related powers have been discussed to explain the mechanism of broadband operation of the dipole. Different behavior of radiations patterns in wide frequency...
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60 GHz Microstrip Van Atta Arrays for Millimeter Wave Identification and Localization
PublikacjaIn this paper performance comparison of co-polarized and cross-polarized microstrip Van Atta arrays working in the 60 GHz frequency range is presented. They can be treated as simple chipless RFID tags with frequency response based identification. Tags with three different nominal resonance frequencies of 57, 62 and 67 GHz are designed by scaling optimized base model. Designed 62 GHz co-polarized and cross-polarized arrays with...
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PREDICTION OF SHIP MOTIONS IN IRREGULAR WAVES BASED ON RESPONSE AMPLITUDE OPERATORS EVALUATED EXPERIMENTALLY IN NOISE WAVES
PublikacjaThe most common methods for predicting ship roll motions in a specified sea state are direct measurements of motions in a representative irregular wave realisation (time domain) or calculations of motions from response amplitude operators (RAOs) in the frequency domain. The result of the first method is valid only for the tested sea state, whilst the second method is more flexible but less accurate. RAO-based predictions are calculated...
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Design of Frequency-Reconfigurable Branch-Line Crossover Using Rectangular Dielectric Channels
PublikacjaThis paper presents an efficient yet straightforward passive reconfiguration technique to tune the operating frequency of a branch-line crossover (BLCO). The underlying principle is to fill rectangular dielectric channels (RDCs) prepared beforehand with either air or materials of different relative permittivity. Two configurations (one RDC and three RDCs in each arm) of the branch-line crossover are employed to estimate the tunability...