We have analyzed the effect of axial guiding magnetic field on the wave dynamics in plasma-beam superheterodyne free electron laser (SFEL) of the Dopplertron type with helical relativistic electron beam in the framework of cubic nonlinear theory. We have found the magnetic field critical values and the saturation levels. We found out that the saturation level of electromagnetic waves is maximal at a certain value of the longitudinal magnetic field strength (the magnetic field critical value). We demonstrated the possibility of a plasma-beam SFEL to generate powerful electromagnetic radiation in the millimeter wavelength range.
Irradiator of dielectric objects with super high frequency field, made in the form of a slot in the end wall of a rectangular waveguide with a dielectric insert inside, was studied experimentally and by calculation. The insert was made in the form of a stopper. The effective irradiation is registered when the VSWR at the system input equals nearly 1. This level can be achieved by means of changing the stopper location. In the math model, the outer region is supposed to be a half-space homogeneously filled with dielectric, which may be dissipative. The geometry of irradiated objects is not taken into account. The frequency region, where an effective irradiation takes place, highly depends on the slot length and on an outer dielectric permittivity. The purpose of the paper is to find the frequency at which the effective irradiation takes place.
Cadmium selenide nanocrystals were prepared in water phase chemistry technique with gelatin, polivinil alcohol, lactose, triton-100 acting as capping agent. Structures were characterized using scanning electron microscopy (SEM), visible absorption and photoluminescence spectroscopies. Influence of component concentrations and technological parameters on nanocrystals average size and properties was studied
In this paper, we propose a novel clutter suppression method based on impulse radio ultra-wideband (IR-UWB) radar system. Unlike conventional moving target indicator (MTI) algorithms, our proposed algorithm can effectively remove clutter signal not only from static objects but also from multipath effects between humans and objects. It can be accomplished by changing the application ratio of clutter suppression algorithm according to the circumstance of radar coverage. It results higher peak to average power ratio (PAPR) and signal to clutter ratio (SCR), so other post-processing likes detection or positioning operates more stable. We evaluate this algorithm's performance by comparing conventional algorithm through some experimental results.
In this paper results of experimental measuring of bright spots of complex shape object in radar range with decomposition method are presented. The main idea of decomposition method lies in providing measurements in near field zone, often in distance of several meters from the object. Due to narrow radiation pattern of the antenna only a fragment of the object will be lightened by the radar situated in the near zone. So, in order to estimate full RCS of the object, a series of measurements must be held. In this work the results of such measurements will be presented and compared with results of numerical testing. This work makes it possible to carry out similar studies for UWB signals in further investigations.
Diffraction of the H-polarized electromagnetic wave by finite system of identical graphene planar gratings is considered. The operator method is used. The scattering operators of a single layer are used and supposed to be known. Scattering characteristics are studied and numerical results are represented.
The generating/detecting methods of Walsh-Barker composite sequences are developed. The relevance of using Barker codes as generating sequences of a composite code intended for generating a synchronization signal is shown, without limitations on the choice of the shape of elementary symbols. The possibility of synthesizing composite sequences with given properties by an adequate choice of elementary symbols and generating sequences is investigated. It is shown that the use of Walsh's orthogonal sequences as elementary ones, introduces the self-synchronization property in the composite Walsh-Barker sequences and a number of new beneficial properties. The orthogonality property of the Walsh sequences and the orthogonality properties of the composite sequences can be simultaneously transmitted on a single carrier of several composite signals, modulated by information symbols. To allocate transmitted information symbols, the matched filtering of the transferred sum is used. The article is followed by diagrams obtained by simulating processes and sequences using the Hewlett Packard © HPVEE Visual Object-Oriented Programming Package. The possibility of simultaneous and independent transmission of various modulated composite sequences are proved. The possibilities of the practical application of composite sequences in perspective telecommunication systems are estimated.
The results of Raman spectra investigation of dielectric Pb 3 (P 0.5 V 0.5 O 4 ) 2 crystallized in pores of synthetic opal are presented. The comparative analysis of these spectra with Raman spectra of Pb 3 (P 0.5 V 0.5 O 4 ) 2 in the monocrystalline state is carried out. Due to fitting o the spectra it was possible to reveal the changes in position of the spectral lines and their half-widths. It was shown that these effects may be caused by changing in the lengths of bonds inside the Pb 3 (P 0.5 V 0.5 O 4 ) 2 molecule as a result of crystallization in nano-sized pores of synthetic opal.
A new invariant to the target Doppler spectrum algorithm of an acoustic signal detection and target localization is suggested. Statistical synthesis of the signal detection algorithm has been carried out under the assumption of a normal signal and noise probability density function for the case of a spatially distributed multi element acoustic antenna. The method developed can be used for both passive and active target localizations. Experimental results are presented.
Excitation and scattering problem for transverse circumferential slots in a shield of coaxial line with dielectric insert just under the slot has been solved. Internal conductivity is determined including multiple reflections that are caused by dielectric insert of a finite length filling the feeder cross-section up. Formulas for radiation and reflection coefficients are presented.
The paper deals with the solution to the challenge of scattering of electromagnetic pulse on a thin-wire model of a radar object. The carrier frequency of the radio-frequency pulse, its duration and shape of the model are the basic data for the challenge to be solved in several stages: calculation of probing radio-frequency pulse spectrum in designated limited frequency range; calculation of RCS model at frequencies from earlier calculated radio-frequency spectrum; calculation of the scattered pulse spectrum; synthesis of scattered pulse. The technique is illustrated on an example of scattering of radio-frequency pulse in thin-wire models of cylinder-and cone-shaped radar objects.
Technique for computing electromagnetic waves scattering by well conducting non-closed screens of finite thickness is considered. This technique is based on employing the E-field integral equation that takes into consideration approximate surface impedance boundary conditions (SIBC). Results are presented of radar cross section (RCS) computation for spherical screens given various values of their conductivity and thickness and various wave lengths in the resonant scattering range.
Numerical studies of the electrodynamic properties of the Fabry-Perot resonator with coaxial-sector apertures and waveguide loads in mirrors have been performed. The possibility of obtaining the circular polarization of the electric field in the volume of the resonator is revealed. It is shown that the polarization of the electric field in the resonator volume can be controlled by changing the distance between the mirrors or the length of the shorted waveguides of one of the mirrors.
The problem of determination of object position in a plane is solved by the analysis of ultrawideband electromagnetic wave reflected from the subsurface object. The model of ground containing perfectly conducting object inside is irradiated by short impulse wave with Gaussian time dependence. The direct problem is solved by FDTD method to receive a time dependence of reflected wave amplitude. To recognize the presence of the object and depths of its position the multilayer artificial neural networks (ANN) is used. The amplitudes of electric component of the reflected field in different time and special points above the ground surface are the input data for multilayer ANN of different structures. The work of the trained ANN is verified for arbitrary depths of object position.
The overview of the high-impulse current measuring shunts with different configurations is presented. The paper looks into some aspects for current shunt sensors, including choices of body types, designs and materials. A current shunt sensor example is presented. This article analyses a current shunt sensor designed for impulse current test with 10 μs front time and 350 μs time to half value waveshape according to IEe 62305-1-2010. The transient response of the shunt was calculated. The requirements to the constructions of the current shunt were defined. The inductance for given construction was calculated. The Joule heating effect for given construction is described.
In this paper, two different extraction techniques are presented to estimate the complex permittivity of materials with high level accuracy. The performances of presented models are discussed to illustrate their potential for obtaining the dielectric properties and composing a database which will is used to identify the unknown materials easily. Furthermore, the composed data base can be used to classify the liquids as safe or unsafe. Moreover, the relationship of between S-parameters and permittivity are showed using estimating methods. The proposed model gives better results as well as analytical and numerical extraction techniques.
The method of microwave dielectrometry was used to measure the dielectric parameters of aqueous liposome suspensions. Based upon measurements of complex dielectric permittivity at a single frequency in the range of bulk water dispersion we were able to estimate hydration of lipid vesicles. It was shown that the magnitude of hydration calculated from the increment of static dielectric permittivity could be used to monitor loading of liposomes with antimicrobial peptide and to track the release of drug from nano-carriers. Redistribution of free and bound water in liposome suspensions upon binding and dissociation of small molecules with lipid membranes of nano-sized spherical particles, precisely traced by dielectric measurements at microwaves, can be used as a diagnostic tool in targeted drug delivery technologies for quality control and monitoring of cargo loading and unloading.
The problem of excitation and scattering of electromagnetic waves by a narrow longitudinal slot filled with a three-layer medium cut in the broad wall of the rectangular waveguide was solved. The mathematical model construction was based on the continuity of the tangential components of the magnetic field on both surfaces of the slot facing to the binding electrodynamic volumes. The magnetic field inside the cavity was considered as the field of sum of the eigenwaves in the waveguide with a three-layer dielectric. The electric field distribution of each eigenwave was used as the basis function in the Galerkin procedure of finding the unknown amplitude coefficients. The effect of the parameters of the dielectric layer on its resonance properties was studied for the longitudinal slot with a dielectric layer located in slot center. The frequency dependences of the elements of the slot scattering matrix were calculated and experimentally investigated.
The modern world is characterized by the pervasive use of computers, sensors, robotics, and Internet connectivity. This represents a new industrial revolution, dubbed Industry 4.0. In this paper, we discuss the application of the Industry 4.0 paradigm to creating a robotic search-and-detection platform intended for humanitarian demining. This is based on the combination and interaction of two microwave radars - including a UWB multi-sensor array, and a holographic imager - as well as 3-D optical cameras, remote navigation, and GPS tracking. The concepts introduced by Industry 4.0 represent an important opportunity for the scientific community to adopt new approaches in the design and use of UWB radar systems, and how data from these systems can be shared, archived, and processed in a decentralized manner accessible to the worldwide community
In this paper, the microstrip to Substrate Integrated Waveguide(SIW) transition bandpass filter is designed and fabricated. It can be used in satellite communication, 5G and radar technology. SIW waveguide conditions and bandpass filter-specific input loss method are used to obtain design parameters. The CST Microwave Studio simulation program was used to simulate the SIW filter with two symmetrical windows. After that the SIW filter was fabricated using the Roger 4003C. It is seen that the obtained simulation results and the measurement values are compatible with each other.
