Proceedings of International Conference on Antenna Theory and Techniques

Frequency domain measurement of permeability of M400HH ferrite rods in the VHF range

2017-07-22T17:14:51+03:00

The frequency dependences of effective magnetic permeability of ferrite rods of the grade M400HH in the VHF range have been obtained by measurement in the frequency domain. These rods can be used in pulse UWB receiving antennas to increase sensitivity in the low frequency part of the VHF range.

Estimation of clutters from aircrafts during ionospheric measurements using incoherent scatter radar with 100-meter two-mirror antenna

2017-07-22T17:14:52+03:00

The analysis of clutters generated by the reflections from aircrafts at distances up to 400 km and received by the side lobes of the antenna pattern of 100-meter two-mirror antenna of the incoherent scatter radar is carried out. The conditions under which clutters arise from aircrafts at an altitude of about 10 km above the earth's surface are determined. Experimental data that illustrate influence of these clutters on the results of ionospheric measurements are presented.

Studying the properties of different materials using terahertz 3D imager radar

2018-02-27T16:33:42+02:00

We have investigated the possibility of studding different materials and configurations of system depending on the distance between the sample and the antenna using absorber. Particular attention was paid to calibrating the system prior to commencement of measurements.

Two-frequency method for probing of ionospheric resonance inhomogeneities

2017-07-22T17:14:57+03:00

The paper studies principles of ionospheric irregularities probed using polyharmonic signals on the example of the two-frequency oscillation which is a beat signal. Authors have considered the interaction of a symmetrical two-frequency signal with an abstract resonant circuit which shows the normalized frequency dependence of the reflection coefficient, typical for resonant inhomogeneities in the form of a periodic structure in the ionosphere.

Measurement method of the object surface deflections using antennas theory

2017-07-22T17:14:58+03:00

The method of remote measurement of object surface deflections using an artificially created system of secondary radiators located on this surface is considered. The physical basis of the method is a change of the pattern of radiators system due to their displacement under the loads influence. Radiators displacements which are included in the expression for the distorted antenna radiation pattern are determined by minimizing of the functional using a genetic algorithm. Reconstruction errors of radiators displacements are identified for different situations taking into account the ambiguity of the problem. The best conditions for the functioning of the method are recommended for the practical use.

Parameters of foam layers definition for calculation of reflection coefficients

2017-07-22T17:15:00+03:00

The work aims to determine the number of foam layers and profile of their dielectric parameters for calculating the coefficients of reflection of foam structures. A foam structure profile depending on its height, quantity of layers and their thickness is defined by measurement of electric characteristics of specimens of foam layers, for example electric resistance (conductivity). Experimental measurements and their results are presented.

Investigation of reflection in the foamed structures

2017-07-22T17:15:02+03:00

The purpose of this paper is to investigate the coefücients of reflection of foam structures as a function of the foaming ratio of foams, the thicknesses of the foamed layers under investigation, and their combination with quasi-homogeneous layers. The investigations were carried out in the open space in the frequency range of 8–12 GHz. Reflection of this range for foams with a foaming ratio of 30, 60 and 170 and for the thickness of the foam samples: 10, 47 and 84 mm. It has been shown that foam layers, both alone and in combination with quasi-homogeneous layers, may be of some interest for the development and fabrication of electromagnetic wave absorbers of a given range for appropriate applications.

Radiophotonic method for instantaneous frequency measurement based on principles of “frequency-amplitude” conversion in Fiber Bragg grating and additional frequency separation

2017-07-22T17:15:03+03:00

This article describes the design principles of optoelectronic system (OES) for instantaneous frequency measurement (IFM) of microwave signals based on the use of amplitude-phase modulation conversion of single optical carrier into symmetrical dual-frequency signal for additional frequency separation, its modulation by unknown frequency and subsequent “frequency-amplitude” measurement conversion in Fiber Bragg Grating (FBG) with Gaussian reflection profile. Such approach allows increasing of measurement resolution at low frequencies.

Effect of the low energy electromagnetic radiation of cell phone frequency (1.8 GHz, 2.4 GHz) on the chromatin state in cells of human buccal epithelium

2017-07-22T17:15:05+03:00

The effect of low energy electromagnetic radiation with frequencies 1.8 GHz and 2.4 GHz on the heterochromatin granules quantity (HGQ) in the nuclei of human buccal epithelium cells was studied. Exfoliated cells were exposed to microwave radiation (frequency 1.8 GHz, surface power density 2.5 μW/cm2; and also frequency 2.4 GHZ, surface power density 2.3 μW/cm2). After exposure to microwaves during 1, 2, and 3 h, immediately or after delay of 1 or 2 h cells were stained with orcein (2% solution in 45% acetic acid). Cell exposure to microwaves induced condensation of chromatin. The biological and medical meanings of the data obtained are discussed.

Optimization of microwave heating of dielectrics taking into account errors in amplitudes of the excitation electromagnetic field emitters

2017-07-22T17:15:07+03:00

The effect of random errors of the currents in the emitters of multi-element radiating system on the efficiency of microwave heating of dielectric is studied. Relationships are obtained for finding the optimal amplitudes of excitation of the emitters, providing on average the best approximation to the desired distribution of electromagnetic and temperature field in the dielectric.

Investigation of processing of dense oily sludge using microwave energy

2017-07-22T17:15:09+03:00

The article considers the perspectives of processing of dense bituminized oil sludge with microwave radiation, including using solvents. The peculiarities of using solvents in the processing of dense bituminized oil sludge with the use of microwave energy are disclosed. The analysis of the obtained results of processing of dense bituminized oil sludge, comparison with the previously obtained results is given.

Retrieving the reflection coefficient of a sample from the frequency response of a special open resonator

2017-07-22T17:15:10+03:00

This paper focuses on accurate measuring the electromagnetic reflection at K band from flat samples made of a composite material or a metal mesh. A special open resonator comprising a sample under test features a good sensitivity due to multiple reflections in the cavity and absence of any contact between the sample and the installation. Data processing algorithm arises from geometric optics description of the microwave field in the resonator. Digital modeling with the CST Microwave Studio software and real experiments with use of ZVA50 signal analyzer confirmed efficiency of the proposed technique.

Technology of wireless transmission of energy to remote objects based on multi-frequency system of transmitters

2018-03-19T14:50:25+02:00

The authors of this work offer a form of application of space-phase-frequency focusing of the V-shaped multi-frequency pulses for the creation of the systems of wireless transmission of energy to land-based, mountain and other difficult-to-reach objects. The creation of overhead, above-water, underground and underwater transmission lines of electric power to such facilities are impossible or impractical for technical, economic and other reasons. Technical feasibility of such systems for wireless transmission of energy to remote objects, and areas of environmental safety for the staff and the local population has been estimated.

Measurements of non-linear sub-THz quasi-optical devices

2018-04-04T17:40:05+03:00

The paper presents recent developments in designing quasi-optical multipliers in the sub-THz frequency domain. An extensive measurement campaign is described in detail in which issues are addressed concerning the non-trivial nature of the problems met. In particular, attention is paid to impedance measurements of the core element, the integrated antenna-multiplier (dubbed the ‘multenna’), together with the associated experimental apparatus for detection of its higher-order harmonics. Finally, use of a light-sensitive semiconducting organic polymer is demonstrated as a tuneable dielectric that will enable elements of a multenna array to be phase-locked for generation of coherent emission.

Two approaches to solving the antenna synthesis problems according to the amplitude radiation pattern

2017-07-22T17:10:58+03:00

A nonlinear synthesis problem according to given amplitude radiation pattern for plane aperture is considered in two ways. An analytical formula for the optimal current is obtained in the first approach. This current generates the amplitude radiation pattern which is close to the given one with the prescribed accuracy. The second approach consists of variational statement of synthesis problem. The numerical results illustrate that each method has advantages in the certain range of frequencies.

Ultrawideband tapered slot, waveguide and dipole antenna arrays

2017-07-22T17:11:02+03:00

This paper offers a review of the most valuable results of antenna array research and development at NTUU "KPI" within the last ten years for ultrawideband radar applications. First, paper describes a novel way to optimize the unilateral tapered slot antenna (TSA) being an element of a wideband scanning array. Second, theoretical and practical results of proposed volume horn array antenna with slant polarization are presented. Third, some result of a novel extension of Munk's current sheet concept is proposed, where the ultrawideband array antenna dipole screened dipole element is substituted by more complicated subarray of dipoles that have different sizes and values of mutual coupling. This approach of ultrawideband radiating panel creation allows to achieve a wide scan angles in orthogonal planes in frequency range with coverage up to 7:1.

Introducing quasi-optical terahertz circular dichroism spectroscopy

2017-07-22T17:11:07+03:00

A sub-Terahertz circular dichroism spectrometer is developed and built based on a vector network analyzer driven quasi-optical system at 220-325 GHz sub-THz frequency domain (VNA-CD). The main goal is to explore the potentially significant absorption features in THz signatures of aqueous protein samples.

Recent advances in computational electromagnetics for microwaves in IRE NASU

2017-07-22T17:11:09+03:00

Recent advances in problem-oriented and generalpurpose microwave-oriented software and applications developed in the department of computational electromagnetics are considered. Numerical-analytical automatic mode-matching based models are extended on the objects given in cylindrical coordinate system. The geometry has to be specified as the set of piece-wise coordinate fragments in Cartesian (MWD1 or MWD2 with account of edge behavior) or in Cartesian or cylindrical coordinates (MWD3) with automatic cross-section geometry recognition and subsequent formation of corresponding modematching technique and S-matrix based numerical algorithms. The future extension to the double-periodical screens and multilayer printed circuits (MWD4) is described moving to terahertz frequency band and “metamaterial” investigations. A set of new microwave devices is proposed which are based on the nonstandard physical principles such as the fringing field interaction, new types of eigen-oscillations of 3D open objects and artificial “optical activity”. They are the band-stop and bandpass waveguide filters, antenna-feed units, polarization rotators, twists etc.

Antenna pattern measurements: UWB impulse and multifrequency signals comparison

2017-07-31T14:07:03+03:00

This paper describes some aspects of wideband (or ultrawideband) measurements of characteristics of antennas which does not require expensive anechoic chambers. The idea of the method is based on exciting the antenna under test by very short impulse which spectrum covers the band of interest and on analysis of spectra of the radiated signals. Reliability of the method is proved by comparison of simulated and measured results of antenna pattern investigations.

Tuning range of microwave devices with micromechanical control

2017-07-22T17:11:17+03:00

The paper presents generalization of micromechanical control principle for number of microwave devices, such as tunable phase shifters and resonator based filters. Starting with one dimensional dielectric discontinuity model, control principle is propagated to microstrip line devices and dielectric resonators. Maximum possible tuning range is discussed along with accompanying insertion loss.

Millimeter-range radiometric system for perspective problems of meteorology and telecommunication

2017-07-22T17:11:19+03:00

Short description of new ground radiometric complex, working on 40 GHz and 94 GHz frequencies and providing remote continuous measurements of full vertical atmosphere attenuation, effective temperature values and liquidwater content of clouds, integral content of vaporous moisture in atmosphere. The feature of the complex is the availability of digital signal processing of detected signals mode.

Adaptive methods of control for signals in the digital channels of the troposphere communication

2017-07-22T17:11:23+03:00

The solution of a scientific problem of determination the informational reliability of the digital channel of troposphere communication with the help of adaptive methods of signal control is currently of great interest. Adaptive methods of signal identification at the output of an adaptive antenna and receiver using signal control and inter-comparison are considered. At the same time the conditions of signal distribution are fixed which allows automatic determination of the informational reliability of the digital channels for the station of digital tropospheric communication.

Achivements in antennas research at Lviv Polytechnic National University

2017-07-22T17:11:26+03:00

This work presents results of research and development of antennas, antenna arrays, polarizers, devices based on plasmon-polariton structures. Mathematical models and computer simulations are developed and tested by researchers of Institute of Telecommunications, Radio Electronics and Electronic Engineering in Lviv Polytechnic National University. Obtained results can be applied for solving various modern ecological, energy, telecommunication and medical problems.

Radome integrated slotted waveguide antennas

2017-07-22T17:11:28+03:00

The development of slotted waveguide antennas with an integrated radome is discussed. The integrated radome is intended to improve the resistance of slotted-waveguide antennas against complex environmental conditions and to extend application areas of the antennas. Efficient approaches to the design, simulation, and fabrication of such antennas are considered. The development of a single plane monopulse Ku-band circular array is presented as an example of the implementations of such approaches. The antenna test results are presented to verify the design, simulation, and manufacturing solutions proposed.

Modeling and optimization of microwave heating in cylindrical volumes

2017-09-25T14:07:56+03:00

This paper considers the problem of formation and optimization of the electromagnetic fields in dielectrics, filling a metal cylinder. The results of mathematical modeling of dielectric heating of liquid in the stream are presented.

Nonlinear composite media on opal matrixes and metallocarbon nanostructures

2017-07-22T17:11:33+03:00

Examination of nonlinear periodic composite media based on opal matrices and metal-carbon nanostructures is conducted. This can constitute a new element base opening possibilities for the modern radioelectronics. The considered nanostructures have the substantial potential for their application in perspective nanotechnologies directed on creation of radioelectronic devices for SHF, EHF and HHF bands (microwave, sub-THz and THz ranges). They allow improving the functional characteristics of the arrangements made on their base. Nanostructures construction with preset properties is important for design of sub-THz and THz radioelectronics. Such properties can ensure an opportunity of nanostructures controlling, based on which it is possible to realize the nonlinear parametric zonal systems (NPS) resonance circuits functioning on current ultraharmonics in the highest zones of electromagnetic oscillations instability.

X-ray optics: Transmission diffractive patterns of large microchannel plates

2017-07-22T17:11:37+03:00

In this contribution we compare experimental and theoretical diffractive data of Micro Channel Plates (MCPs) in transmission mode. We evaluate the transmission efficiency of different optical devices at different energies of the primary X-ray radiation in the normal incidence geometry. Data were collected performing angular scans of both the MCP device and of the detector in the range of a few degrees. We analyzed MCPs of 33 mm and 20 mm diameter and ~300 μm thickness, having circular micro-channels of 3.4 μm directed normal to the MCP surface. Quite symmetric patterns of increasing complexity from high to low photon energy have been collected. Their shape and intensity are in reasonable agreement with preliminary simulations.

Odd symmetry of weights vector in linearly-constrained adaptive arrays with desired signal

2017-07-22T17:12:11+03:00

The paper discusses the conditions of an odd symmetry in linearly-constrained least squares criterion adaptive array. It is shown, that the vectors, which optimal weight vector of such adaptive array consists of, and the optimal vector itself, have an odd symmetry, i.e. pairs of symmetrical elements of the vectors are complex-conjugated. To ensure this property, the vector of constrains (radiation pattern values in directions of interest) has to be specified as a real-valued ones. The odd symmetry allows to calculate the weights of the adaptive array in real-valued arithmetic at the cost of two or four times less number of arithmetic operations, comparing with similar calculations, based on complex-valued arithmetics. Adaptive algorithms, based on real-valued arithmetics, provide a 1.5 … 2 times shorter transient response and a 2 … 3 dB deeper notches in the steady-state radiation pattern towards interference sources comparing with complex-valued algorithms.

Analysis and optimization of the decoupling in antenna systems consisting of antenna arrays

2018-03-19T14:35:49+02:00

Two problems of achieving the required decoupling in antenna systems have been studied: in the first problem, the required isolation was achieved by changing the phases of the PRS currents, in the second case due to the change in the parameters of the impedance decoupling structure.

Frequency and pattern reconfigurable antenna array based on liquid crystal technology

2017-07-22T17:12:15+03:00

A reconfigurable antenna array based on liquid crystal (LC) technology is proposed, which can dynamically tune operation frequency and achieve beam steering. The antenna element is mainly composed of two parts: a microstrip series patch array and an inverted microstrip line (IMSL) phase shifter. The LC substrate is used to support the patch array for controlling its resonance frequency, while the LC-based IMSL phase shifter is adopted to tune the transmission phase by changing the effective permittivity of the LC through a DC bias voltage. In order to verify the reconfigurable characteristics of the antenna, the antenna array consisting of 1×4 elements are designed and numerically investigated. Simulation results show that this antenna can realize beam steering with a scanning angle range of (-20°, 20°), while its operation frequency can be actively tuned between 14.5 GHz and 16.4 GHz. The proposed antenna configuration is a promising candidate, which has potential application in communication fields.

Radiation, scanning and matching characteristics of the new design of phased antenna array of printed bow-tie dipoles

2017-08-11T14:39:20+03:00

A new robust design of the printed phased antenna array was developed and investigated. Results of numerical prediction of radiation, matching and scanning characteristics of a single printed bow-tie antenna and a new design of phased antenna array composed of these radiating elements are presented.

Cylindrical antenna array development and measurements for DOA-estimation applications

2017-07-22T17:12:19+03:00

The article discusses the functioning of the radio direction-finding methods in the system of cylindrical antenna arrays formed of the designed radiators, directional factor of which is not equal to 1. The accuracy of determining the angular azimuth coordinates with the direction-finding method with super-resolution MUSIC is estimated in azimuth plane.

Random incoherent antenna arrays focused in the near field zone

2017-07-22T17:12:21+03:00

In this article we have examined the properties of incoherent arrays, focused in the near field zone, developed a mathematical model for calculating the parameters of different kind of incoherent antenna arrays, such as size of focusing area, dependence of focus area on pulse duration.

Mutual coupling influence on parameters of arc E-plane antenna array of vibrator radiators

2017-07-22T17:12:22+03:00

This article presents numerical investigation of the E-plane arc antenna array of vibrator radiators as an example of nonplanar and non-rectilinear array which parameters are influenced by mutual coupling. The simulation results are shown in charts. They include dependences of active and reactive part of the impedance and E-plane radiation pattern from different parameters caused by mutual coupling in antenna array.

Radiation pattern of linear antenna array with control of directivity and supper-selectivity properties

2017-07-22T17:12:24+03:00

Improved linear antenna array design capable of obtain the given side-lobe suppression with controlled value of antenna directivity is suggested. The antenna of supper selectivity properties is also suggested. A clear linear antenna design procedure has been presented that does not require the implementation of numerical optimization procedures. The efficiency of suggested design has been investigated.

Planar Ku band antenna for perspective telecommunication facilities

2017-07-22T17:12:26+03:00

The deployment of a new generation of communication systems requires the development of high-frequency ranges of wavelengths. The paper deals with a promising class of millimeter band performed on the basis of different types dielectric wave-guides. The methods of the engineering design of these antennas are presented. It is shown that the considered antenna can serve as the basis for a family of antennas with characteristics suitable for new telecommunications applications.

W band patch antenna array for Maglev smart grid technology

2017-07-22T17:12:29+03:00

A patch antenna array is presented to be a part of an antenna system for Maglev smart grid technology operating at a frequency of 95 GHz which corresponds to the middle of the second atmospheric transparency window. Simulation results of 2x2 patch antenna array element are demonstrated and discussed for an optimized array and feeding circuit topology at the operating frequency.

Evaluating the influence of intrasystem perturbations of the observations covariance matrix on the DF response of adaptive antenna array

2017-07-22T17:12:31+03:00

In development of an analytical approach to study the class of inverse problems with correlation matrix of observations inversion the expressions that showing the behaviour of direction of arrival (DOA) response of adaptive antenna array under intrasystem uncertainty are obtained. The value intervals for correctly representation of solved problem in the relation to maximum entropy and Capon's methods are defined; DOA reliefs which allow evaluating the perturbations influence of the correlation matrix with different conditionality on the characteristics of the antenna array are built.

Spatial distribution of the amplitude of electromagnetic waves in the near zone of linear and flat antenna arrays

2017-07-22T17:12:34+03:00

The amplitudes and phases of the electric field in the near zone of the linear and planar equidistant antenna arrays of a large electrical length on the basis of a radiating coaxial-slit cable, that are designed to provide reliable radio communication in the underground tunnels and at the railway transport, are calculated. It is shown that such antenna arrays have shaped a searchlight beam in the near zone upon condition that three or four linear radiating cables have radiated.

Electrodynamics algorithm of calculation of horns phased antenna array

2017-08-15T14:26:12+03:00

A new approach to the analysis of the radiation problems of the linear waveguide array is presented. The problem of radiation from the linear waveguide phased array for the case scan in H-plane is considered. Electrodynamics algorithm built in a Cartesian coordinate system on the basis of method of cross-linking, method of the extended area and using the machine of the Green function. The horns in H-plane have a finite thickness of common wall. The electrodynamics parameters depending on the normalized geometric dimensions of emitters have been calculated.

Effect of the ground screen on sensitivity of low-frequency radio telescope array element

2017-07-22T17:12:37+03:00

The Giant Ukrainian Radio Telescope (GURT) is a new generation radio telescope with active phased antenna array intended to operate within 10–80 MHz range. The radio telescope is being constructed now in Ukraine. The array elements are active antennas in form of flat wire dipoles integrated with low-noise preamplifiers. In the paper we present a comparative analysis of two GURT array element versions that differ in presence or absence of wire grid ground screen under the dipole. The analysis results are given and discussed.

Array of the two arc monopoles on a sphere with surface impedance

2017-08-17T11:49:34+03:00

The antenna array of two arc monopoles which are located parallel to the surface of a perfectly conducting or impedance sphere is considered. The influences of the phase of excitation of a monopole, the distance to the sphere surface, and sphere radius and its surface impedance on the directivity of the radiator are considered. It is shown that the radiation pattern of the antenna for antiphase excitation is highly directional and has a single maximum in the plane of arrangement of the emitters.

Features of photonic beamformer model based on DWDM approach and fiber dispersion

2017-07-22T17:12:41+03:00

The main features of the photonic true time delay beamformer model for phased array antenna in the receive mode are investigated and experimentally tested. The performance characteristics of the key components of photonic beamformer based on DWDM technology and fiber chromatic dispersion are examined and specified. A five channel beamformer prototype is built using the components available on the market of fiber-optic analog communication links and tentatively investigated. 5-element microwave linear array antenna far-field patterns in 6–18 GHz frequency range have been measured which demonstrated the designed model beamforming features for antenna pattern shifted up to 40°. The results of experimental testing agree with the calculated estimates.

Choice of number, structure and placement of compensation modules in the radar with planar PAA

2017-07-22T17:12:43+03:00

The paper addresses adaptive systems for noise jamming protection of the radar with a planar phased array antenna (PAA). Basing on results of mathematical simulation, the number of compensation channels formed of modules of a 10,000-element planar square PAA containing 625 (400; 100) modules of the size 4×4 (5×5; 10×10) is substantiated. Their arrangement and a structure of a system of the channels, either in the presence of Taylor (or Hamming) weighting of output signals of the modules (or elements) or in its absence, for effective extracting of signals embedded in noise jamming is studied. A necessary degree of the increase in the number of such channels in the presence of non-identities is estimated.

Origins of the digital antenna array theory

2017-07-22T17:12:46+03:00

The origins of the digital antenna array theory are presented in this paper.

Equipment optimization for weather balloon and ground-based weather stations using GNSS

2017-07-22T17:14:28+03:00

A simplified construction of the equipment of a weather balloon and weather station with the application of GNSS functionality is presented in this study.

Analytical description of polar coordinates of random vectors in case of arbitrary fluctuations its Cartesian coordinates

2017-07-22T17:14:30+03:00

There are many tasks where analytical description of the random signals is used. For instance, representation of signals and waves in polar coordinates is widely used in antenna theory and techniques. In this report, we present the results of implementation of the polygaussian approach for describing polar coordinates of random vectors as mixtures of Rayleigh and Rice distributions. Moreover, polygaussian approach gives an opportunity to generalize it to the case of multidimensional vectors.

Segmentation for detecting buildings in infrared space images

2017-07-22T17:14:31+03:00

The given work describes a new technique of image segmentation, in particular for building detection on radar or infrared Earth-observation images. The method is based on property of most man-made objects which consist in straight edges and mostly right angles. The developed 2D adaptive image filter assists to detect straight edges even if given image fragment has a low contrast and has been extremely noised, in addition, if an object edge has been distorted, for example, by interference in the SAR azimuth channel, the filter compensates for distortions which do not exceed the specified value. The next processing of line-segment list without image raster works faster and allows detecting a relatively small set of possible targets. This approach could be used as addition for neural networks as well as provide assistance in preparing of training data set.

DOA estimation using beamspace root-music based estimator bank

2017-07-22T17:14:34+03:00

The estimator bank approach allows improving the performance of direction of arrival (DOA) estimation in the area of low signal-to-noise ratio. In the paper, the estimator bank is formed from the modified Beamspace Root-MUSIC estimator using resampling by adding pseudo-noise. The illumination of outlying roots of the modified beamspace Root-MUSIC polynomial is used instead of elimination of entire estimator.

Remote sensing of plane-layered media with losses using UWB signals

2017-07-22T17:14:35+03:00

The previously proposed method of inverse scattering problem statement and solution for plane-layered media is extended for the media with the losses (taking into account conductivity of the medium). As before, algorithms of processing of pulse signal reflected by plane structures which was proposed by the Authors constitute the method base. The advantages of this approach are combination of the information content of the UWB pulse signals and the efficiency of algorithms for solving inverse problems. For processing and interpretation of the experimental data, the Newton-Kantorovich scheme in the frequency range is used. Using developed software, series of experiments on the processing of GPR pulse signals in sensing plane-layered medium (road pavement) is carried out. The obtained results allow to optimize values of the pulse signal parameters. Also, the obtained results can be used in biomedical research and in non-destructive testing of industrial facilities.

Radiophotonic method for spectrum analysis of SHF-band signals based on stimulated Mandelstam-Brillouin scattering

2017-07-22T17:14:37+03:00

In this article, we present the results of research of photonic systems for spectrum analysis of the SHF-band radio signals based on “frequency-amplitude” transformation in contours of amplification or absorption of stimulated Mandelstam-Brillouin scattering (SMBS) approximation in single-mode optical fiber. Using of such systems as a means of spectrum analysis of the SHF-band radio signals allows us to eliminate many of the shortcomings of similar systems.

Identification approach for determining radio signal frequency

2017-07-22T17:14:39+03:00

The article deals with method of spectral analysis of radio, which can be useful for receiving signals by undirected antenna. The main problem of this analysis is to find the central frequency of a sinusoidal oscillation when observed object is hidden in noise. Typically this problem is solved by estimation of unknown frequency by least square error method. In this paper, iterative technique that can be used in panoramic receiving set is proposed. The advantage of the new estimator is its computational simplicity.

Radio signal distortion assessment by non directional antennas of the helicopter

2017-07-22T17:14:41+03:00

The cause-effect relations between the levels of pulsations of the antenna system, caused by main rotor rotating of the helicopter, and the probability of the bit error occurring in the digital data transmission channels were established. Graph-analytical method of error probability estimation was developed.

Method of adaptive selection of channel number in MIMO system

2017-07-22T17:14:42+03:00

In the work offer method of adaptive choosing number channels in MIMO system with saving bit error probability under specified border. Method allow to work with small attitude signal/noise in mode with limited number parallel channels transfer.

Experimental evaluation of the shading effect of accelerating lens in azimuth plane

2017-07-22T17:14:44+03:00

When using an accelerating metal-lamellar cylindrical lens to increase the signal level towards the remote subscriber of the wireless access system, a shadowing effect can be exerted on users outside the main lobe of the radiation pattern of this lens. The report presents the results of an experimental study of the field structure in the azimuth directions, different from the axis of the lens, oriented to the priority subscriber. The characteristics of the developed and manufactured software-hardware model, including metal-lamellar lens; a device for generating a data packet and emitting a signal; set of receiving sensors; the necessary software for the collection and processing of results. The measurements carried out under typical conditions showed that the “shading” sector estimated by (signal + noise) / noise ratio for the lens starts at about 6° with respect to the lens axis and ends at 30°.

Combined antenna of unmanned aircraft vehicle for early warning system against dangerous wind shears

2017-07-22T17:14:46+03:00

Possibility to create the low budget combined airborne antenna (CAA) for early-warning system (EWS) against dangerous vortexes and wind shears when landing transport unmanned aircraft vehicle (UAV) is discussed in the report.

With such an antenna the well-known method of inclined radioacoustic atmospheric sounding (IRAS) in its aviation modification is being implemented. The electro-spark acoustic generator (ESAG) of the original construction takes on the role of a generator of the pulse acoustic radiation directed at the nadir. Application of standard airborne equipment of Doppler velocity and drift angle gauge of an aircraft (DVDG) as a component of EWS is a low budget basis of CAA.

Obtained data of airborne IRAS equipment power budget proves the success of the proposed way of EWS equipment construction with the combined acousto-electromagnetic antenna.

Quasi-optical approach to the analysis of the energy model of millimeter wave propagation and antenna characteristics

2017-07-22T17:14:49+03:00

Millimeter-wave communication systems, unlike, for example, classical ones operating in the decimeter wave band, have fundamental differences related to the formation, radiation, propagation properties and signal losses. A new quasi-optical approach to the estimation of the energy losses of the millimeter wave (MMW) radiation and antenna amplification is proposed in the article. Such method makes it possible to construct a loss and interference model for the millimeter wave band (MMB) under conditions of direct visibility over greater than one kilometer distances and multipath propagation models in small cells of mobile systems in urban conditions.

Compact polarization plane rotator for arbitrary angle

2017-07-22T17:13:23+03:00

We have studied the possibility to design a compact polarization plane rotator of electromagnetic waves based on the structures with dihedral symmetry. Proposed structure allows rotation of polarization plane at arbitrary angles and has acceptable loss in given frequency band.

Novel high performance coherent dual-wideband orthomode transducer for coaxial horn feeds

2017-07-22T17:13:24+03:00

In this paper we present the design and simulated characteristics of a novel high performance coherent orthomode transducer to be used in dual-wideband coaxial horn feeds of reflector antennas with polarization diversity or polarization processing of radio signals. The main stages of the development process are described. For both polarizations the simulated VSWR is less than 1.06 within both operating frequency bands (3.4–4.2 GHz and 10.7–12.8 GHz). Calculated crosspolar isolation is higher than 70 dB. Simulated differential phase shift between the output signals with orthogonal linear polarizations is less than 1° in both operating frequency bands.

Dual band feed horn for mm-wave applications

2017-07-22T17:13:26+03:00

This study introduces the design of the dual band coaxial horn to be used as a feed for dual reflector systems. Complete numerical investigation has been performed in the operating bands of the horn, including return loss, radiation patterns and tolerance analysis. The proposed design of the feed horn including dielectric radome is fabricated.

High performance extended C-band 3.4–4.8 GHz dual circular polarization feed system

2017-07-22T17:13:27+03:00

The design, main stages of development process and simulated characteristics of a high performance extended C-band 3.4–4.8 GHz feed system for reflector antennas of dual circular polarization satellite communication earth stations are presented in this paper. The feed system includes an iris polarizer, a 45° square waveguide twist-transition, and an orthomode transducer based on a double-ridged junction. All these components have been optimized for the operation in extended C-band 3.4–4.8 GHz. VSWR of the developed dual circular polarization feed system is less than 1.14, its crosspolar isolation is higher than 30 dB.

Use of structure symmetry for the design of passive microstrip devices

2017-07-22T17:13:53+03:00

Approach to development of calculation methods of passive microstrip devices with symmetric structure based on the input impedances of partial schemes received by use of even-odd excitation of symmetric multiport are offered in the work. The expressions relating the input impedances of partial schemes of the transforming four-pole circuit and the directional four-port circuit with their scattering parameters are given. Features of usage of input impedances method for the design of different microstrip devices, including those on the basis of coupled line segments are considered.

Forming the sensitive area of microwave motion sensor

2017-07-22T17:13:55+03:00

In this work the results of research of microwave motion sensor on the basis of the integrated antenna-oscillator are presented. The option of realization of such sensor with modulation of the electromagnetic oscillations reflected back from the explored object is represented. Influence of the change of frequency of generating oscillations, caused by modulation mode, on forming of sensitive area of the sensor is shown.

Investigation of 3D printed dielectric structure for microwave lens prototyping

2017-07-22T17:13:57+03:00

In this work, we designed and fabricated dielectric materials with predetermined dielectric permittivity. These materials are 3-D printed using fused deposition modeling technique with high impact polystyrene filament. The dielectric structure is composed of discrete layers that are separated into cells. Each unit cell is essentially a plastic cube with square air void in the center. Desired variable relative permittivity was realized by changing the filling ratio. The dependences of relative permittivity on filling ratio are measured and presented. Obtained approximated dependence of relative permittivity can be utilized for microwave lens synthesis for low-cost communication systems.

Tunable RX filter with ferroelectric capacitors for DCS, PCS and UMTS communication systems

2017-07-22T17:14:01+03:00

A new structure of a bandpass filter with steep left slope of the frequency response, tunable by ferroelectric capacitors, is proposed. The filter can be used in receiving channel (RX) in communication systems of DCS, PCS and UMTS standards. The computer simulation of the frequency responses of the filter has been performed for the following conditions: feasible parameters of ferroelectric capacitors; small capacitance range Cmin/Cmax < 2; relatively large minimum capacitance Cmin > 0.4 pF; low quality factor Qc.

Unconventional connection of ferroelectric capacitors to resonators in tunable filters

2017-07-22T17:14:03+03:00

Unconventional connection of ferroelectric capacitors to resonators of tunable filters is proposed. It has increased the required minimum of capacitance value and the frequency range from ku-band to K-band. The proposed method of connection is illustrated by an example of microstrip filter, which is tunable within the frequency range 18–20 GHz. The minimum capacitance of the ferroelectric capacitor, that was obtained, was Cmin = 0.22 pF, the maximum value — Cmax = 0.31 pF. In traditional connection scheme, capacitance value is Cmin = 0.11 pF, and it is not possible to implement ferroelectric capacitors in this case. Simulation results of the frequency responses of the filter are presented.

Fabry-Perot resonator with evanescent coaxial-sector holes

2017-07-22T17:14:05+03:00

The Fabry-Perot resonator is actively used in optical microwave devices. Frequency-selective properties of a Fabry-Perot resonator formed by plane screens of finite thickness with coaxial-sector apertures are investigated. An analysis of this resonator has shown the possibility of obtaining the total transmission of a plane linearly polarized electromagnetic wave through evanescent holes with a very strong localization of the electromagnetic field in the resonator volume.

Bragg structures with thin lossy layers

2017-07-22T17:14:07+03:00

The behavior of quasi-periodic and aperiodic (chirp) Bragg structures with thin lossy layers was examined. In order to determine the frequency dependence of the reflection coefficient transmission matrix method was used. A deep minimum of the reflection coefficient for any frequency is implemented by proper choice of the thickness of the last thin film and its optical distance to the substrate. The possibility of providing broadband reflection by aperiodic structures has been offered.

Packet suppression of a leakage of microwave power from industrial heating systems via the higher modes of open waveguide ports

2017-07-22T17:14:09+03:00

A waveguide bandstop filter intended for an open port of an industrial heating system is numerically modeled. The filter was designed to suppress a leakage of microwave power from a magnetron operating the frequency of 2.45 GHz. A modification the filter providing an improved suppression of a power leaking via higher waveguide modes is proposed. A reduced leakage level is obtained without enlargement of the microwave filter.

Adaptive control of hybrid modes in a longitudinally magnetized gyroelectromagnetic circular waveguide

2017-09-14T16:38:06+03:00

In this report, dispersion properties of a circular waveguide filled by a composite gyroelectromagnetic structure, which consists of alternating ferrite and semiconductor layers are studied. The system is supposed to be longitudinally magnetized, i.e. the static external magnetic field is applied along the axis of the guide, perpendicularly to the layers of the structure. The system is considered to be in the subwavelength regime, and the relative effective permittivity and permeability of the waveguide filling are introduced. The waveguide dispersion equation and its eigenmodes are derived. Unique dispersion characteristics of supported hybrid modes are investigated. It is shown that simultaneous presence of gyromagnetic and gyroelectric eifects in the waveguide system can gain a substantial control under the dispersion characteristics and field distributions of the supported modes.

Coupling of waveguide with resonator through diaphragm with slot with dielectric slab

2017-07-22T17:14:13+03:00

The problem of coupling of a semi-infinite rectangular waveguide with a resonator through the narrow slot in their common end wall is solved. The slot is completely or partially filled with a dissipative dielectric. The changes in the behavior of the reflection and absorption coefficients of the feeding power are studied as a function of the dielectric constant and the thickness of the diaphragm.

Features of the dispersion characteristics of planar dielectric waveguide-grating system

2017-07-22T17:14:15+03:00

In this work, the results of experimental study of eigen waves of periodical system that is formed of planar dielectric waveguide and grating are presented. Authors describe the features of system mode composition in frequency range of the second-order mode excitation. Also, the signs of inter-type mode transformation were detected.

Helicon isolator with quarter-wave nonreciprocal transformer

2017-07-22T17:14:16+03:00

The problem of design of the helicon isolators for the bottom of HF band is discussed. The usage of the quarter-wave helicon resonator with single-side metallization is proposed. Simulation and experimental results are presented.

Autodyne effect application for stability analysis of the steady-state mode of UHF oscillating systems

2017-07-22T17:14:18+03:00

The autodyne characteristics are oifered to use for steady-state stability analysis of the UHF oscillators. Theoretical substantiation of the proposed method is performed on an example of the oscillating system's mathematical model presented in the form of two mutually-locked partial oscillators under a condition of strong coupling between them. Peculiarities of stable functioning zones for oscillating systems are described at different partial oscillator parameters and for various conditions of their mutual coupling. Experimental investigations are performed based on the 8mm-wavelength range double-diode oscillator.

Signal analysis of a double-diode autodyne

2017-07-22T17:14:20+03:00

Analysis results of autodyne signals of the double-diode oscillator, which is under influence of the proper reflected emission from the moving object, are presented. The analysis is performed on the base of the autodyne mathematical model presented in the form of a system of two mutually-locked partial oscillators under condition of strong mutual coupling. Peculiarities of signal formation are considered for various parameters of partial oscillators and coupling conditions. Experimental data are obtained for the 8mm-range Gunn double-diode oscillator of the flange type.

Radiofrequency deterministic chaos oscillator based on a transistor structure with negative resistance. Numerical researching

2017-07-22T17:14:21+03:00

The deterministic chaos mode in a basic circuit of a radiofrequency oscillator based on a bipolar transistor structure with negative resistance have been studied in this paper. Experimental research results for parameters and characteristics of the bipolar transistor structure with negative resistance have been obtained. Chaotic dynamics of the generated oscillation has been explored. Feasibility of connecting a symmetrical dipole antenna to create a transmitter with chaotic carrier has been estimated.

Influence of the autodyne oscillator coupling degree with antenna upon its transfer and noise characteristics

2017-07-22T17:14:24+03:00

Analysis results of coupling degree influence of the autodyne oscillator with an antenna are presented together with influence of the impedance characteristic type (soft or rigid) of the active element on the coefficients of autodyne amplification, autodyne frequency deviation and power transfer as well as on the noise parameters and characteristics. Analytical and numerical calculations of above-mentioned parameters and characteristics are performed, and results of experimental investigations of the 8mm-range Gunn diode autodyne are given.

Coaxial horn antenna and its usage perspectives in ground-penetrating radar systems

2017-07-22T17:14:26+03:00

The design of a cylindrical coaxial horn antenna with a generatrix bend and the central conductor mounted along its axis is proposed. Two constructions types (varieties) of such antenna are studied. In the first case, such conductor is a metal-dielectric rod, which does not reach the throat of the horn. In the second one it is a copper rod, reaching the throat of the horn. Experimentally confirmed that for certain sizes of the rod such antenna constructions provide reduced width of the antenna pattern by 12° and allow to receive electromagnetic wave with arbitrary polarization.

Numerical solution of nonlinear spectral problems in syhthesis theory of antennas with flat aperture

2017-07-22T17:11:41+03:00

Numerical method for solving the nonlinear two-parameter spectral problems arising in nonlinear synthesis theory of antennas with a flat radiating aperture is considered. The numerical algorithms to find the connected components of the spectrum of linear homogeneous two-dimensional integral equations which describe the branching lines of solutions of synthesis problems of the flat apertures and antenna arrays according to the prescribed requirements to amplitude directivity pattern are constructed and justified. For the case of rectangular aperture the analysis of branching of the solutions of basic equations of synthesis with using the proposed method is presented. Results of numerical experiments are given.

Near-field calculation for reflector antenna with shape of asymmetrical cutting from a paraboloid of revolution

2017-07-22T17:11:43+03:00

Radiation field calculation method is considered for reflector antenna in its near-field region. The method is based on using field integral representations for reflector antenna obtained with Lorenz reciprocity theorem. The mirror edges contribution to antenna full field is considered using solving simulative problem of plane monochromatic wave diffraction at perfectly conducting wedge. The near-field calculation results for reflector antenna with shape of asymmetrical cutting from a paraboloid of revolution are presented.

Radiation fields of a radial dipole located on a metal sphere coated by a layer of metamaterial

2017-09-06T17:50:39+03:00

Radiation fields of a radially oriented dipole located on a metal sphere coated with a thin layer of absorbing metamaterial are investigated. Numerical simulations were performed by using the electric Green's function for the space outside of an impedance sphere. An impedance of the metamaterial layer required to minimize the influence of the spherical scatterer with resonant dimensions upon the directivity of the dipole radiation in the wave zone was estimated.

Electromagnetic near-field of circumferential slot cut in coaxial line shield

2017-07-22T17:11:48+03:00

The problem of determining the electromagnetic fields, created by slotted coaxial line, is solved in the present work. To determine the coaxial-slot antenna near-fields the Kirchhoffs method has been applied. Electromagnetic field distributions in the near-zone of coaxial-slot radiator have been explored for different values of feeder parameters on a large range of wavelengths. Field diffraction patterns for the short distances from the slot radiators have been obtained.

Electromagnetic fields in the near-zone of aperture antennas with round opening

2017-07-22T17:11:50+03:00

Using the vectorized Kirchhoff integral, the external problem of electrodynamics is solved for emission of continuous aperture antennas with a circular shape radiating opening. The mathematical support was developed and calculations of amplitude and phase characteristics of electric and magnetic fields in the direction of the normal to the radiating opening and on plane surfaces parallel to the opening were carried out, the amplitude and phase distribution of the field sources being constant, the change in the opening diameter from half to 100 wavelengths. It is shown that the searchlight beam in the near-zone of such antennas is formed, diameters of the radiating opening being larger than 1.5–2 wavelengths, the amplitude of electric and magnetic fields oscillate uniformly over a larger range of values compared with cases of square and rectangular opening.

Directional properties of linear and V-antennas

2017-07-22T17:11:52+03:00

The method for calculating directional characteristics of thin antennas with large dimensions: directional patterns, directivity, pattern factor is proposed. The analytical expressions are determined, and characteristics of metal dipoles, V-dipoles and analogous in-phase radiators are calculated. The importance of accounting the pattern factor for the estimate of a communication range is shown. The advantage of in-phase radiators is demonstrated. The possibility of an employment of the given radiators as elements of directional antennas and antenna arrays is considered.

Director antenna with in-phase currents

2017-07-22T17:11:54+03:00

The method of calculating directional characteristics of director antenna: directional patterns, directivity, pattern factor is proposed. The analytical expressions are determined, and characteristics of antennas with metal dipoles, with V-dipoles and with analogous in-phase radiators are calculated. The advantage of in-phase radiators is demonstrated. It is shown that the director antennas with linear and V-radiators with in-phase current distribution provide high directivity in a wide frequency range. The task of optimization of considered antennas by methods of mathematical programming is stated.

Log-periodic antennas with in-phase currents

2017-07-22T17:11:56+03:00

The approximate method of calculating directional characteristics of log-periodic antenna: directional patterns, directivity, and pattern factor is proposed. The analytical expressions are determined, and characteristics of antennas with straight metal dipoles and with in-phase radiators of the same dimensions are calculated. The advantage of using in-phase radiators is demonstrated. It is shown that the log-periodic antennas of radiators with in-phase current distribution allow to decrease the antenna length and to provide the high directivity in a wide frequency range. The problem of optimization of considered antennas by methods of mathematical programming is stated.

Artificial neural networks in time domain electromagnetics

2017-07-22T17:11:57+03:00

The application of artificial neural networks (ANN) is considered to the problems of electromagnetics in time domain. Amplitudes of electromagnetic field in definite points of observation in different moments of time are proposed for using as initial values for an input layer of neural network. As examples the different structures of ANN were applied to solve the problem of determination of layered medium parameters by reflected transient field analysis. The incident field is plane wave with Gaussian time dependence. The stability of the determination of medium geometrical and electrical characteristics is studied for the case of presence of experimental errors, outer interferences, and instabilities of medium parameters.

Airy pulse transformation on time-spatial jumps of refractive index

2017-07-22T17:12:00+03:00

Transformation of an electromagnetic pulse in a triply asymmetric electrodynamic problem is considered: transformation of an initial asymmetric Airy pulse on a boundary between two dielectric medium in one of which the refractive index changes in time by jump.

Excitation of the nonmagnetic isotropic media with linear dependence characteristic impedance along the direction of plane wave propagation

2017-07-22T17:12:02+03:00

As one means to solving propagation problems are considered modeling of electromagnetic wave in inhomogeneous layered media. There are exact relations for the field exciting by the plane monochromatic electromagnetic wave in flat-layered one-dimensional inhomogeneous isotropic media is used in this paper for analysis field structure in media with linear dependence characteristic impedance along propagation directions.

Analysis of axially symmetric diffraction grating

2017-07-22T17:12:04+03:00

Effective calculation technique for periodic structures is proposed in this paper. The grating possesses a lot of periods and is difficult to be calculated with usual methods. The proposed technique is based on well-known Finite Difference in Time Domain method for Body of Revolution (BOR FDTD). The method implementation for small-scale grating situated in a hollow dielectric waveguide is shown. Mentioned method is developed for structures with lossy dielectric. In order to restrict calculation domain absorbing boundary conditions is provided in the form of Perfectly Matched Layer (PML). Numerical calculations for different gratings are provided, the obtained results are analyzed.

Performance evaluation of an improved ITU-R rain attenuation prediction model over Malaysia equatorial region

2017-07-22T17:12:06+03:00

Attenuation due to rainfall is one of the most fundamental constraints on the performance of satellite links above 10 GHz. This work presents the results of rain attenuation measurement using radar data collected from MMD and DIDM Malaysia. The results were compared with newly improved ITU-R P530-16 and four other selected tropical rain attenuation prediction models. The statistical analysis showed that ITU-R P 530-16 has significantly addressed the problem of rain attenuation underestimation prediction as presented by older version of the recommendation.

Active and reactive energy of electromagnetic waves

2017-07-22T17:12:09+03:00

The concept of active and reactive energy of electromagnetic waves are introduced to the scientific circulation and complete the formation of concepts of the wave theory as a section of electrodynamics. Algorithm for separation of active and reactive energy of electromagnetic waves is mathematically and physically justified. Importance of such separation of active and reactive energy of electromagnetic waves is shown on the example of the propagation velocity of wave energy in a lossy medium. Results can be also applied to analysis of wave propagation processes in the intermediate zone of Hertzian dipole and adjacent reagions.

Variants of the double-frequency GPS antennas

2017-07-22T17:12:47+03:00

Three designs of antennas for GPS system are analyzed in this article: the conical spiral antenna, the micro-strip antenna and the cylindrical spiral antenna.

Near field zone of the UWB bow-tie dipoles

2017-08-28T15:11:53+03:00

The experimentally obtained time-amplitude dependences of near-zone EM fields of the UWB planar “bow-tie” radiators have been presented in the work. The dependence of post-pulse oscillation amplitudes on the radiator shape and the magnitude of load resistance have been investigated. Conditions of the effective radiation of EM pulses with a required amplitude and the least long-drawn-out and amplitude-suppressed post-pulse oscillations have been determined.

Combining electric and magnetic dipoles in the construction of antennas

2017-07-22T17:12:51+03:00

It was shown that for antenna bandwidth extending insufficient to use electric or magnetic dipoles separately. As was proved experimentally that the combination of electric dipoles with magnetic dipoles enable to attain antenna bandwidth increasing more than two octave. Using the example of a combination of electric radiators it is shown that the matching band can be extended to the low-frequency region. The design of an electrically small ultra-wide band antenna is proposed. The dimensions of the antennas do not exceed 1/5 of the frequency wave length. The antenna directional patterns in the main planes are close to the cardioid.

Modeling of ultra-wideband antennas for multi-purpose broadband systems

2017-07-22T17:12:52+03:00

Results of modeling of some printed antennas for broadband systems for various purposes are considered. The problems are solved by the method of moments. Modeling of disk monopole, modified Sierpinski triangle and Vivaldi antenna was performed. Considered antennas can be used in the range of 0.9–6 GHz applications.

Active loop sensor for receiving pulse magnetic fields of nanosecond duration

2018-02-26T15:53:16+02:00

The active magnetic field sensor consisting of a loop with 40 mm in diameter and a transimpedance amplifier has been developed. The rise time of the transient response of the sensor is 0.45 ns and the conversion factor of the magnetic field strength to the voltage at the sensor output is 2.5 V/Am−1. The amplifier dimensions are 10×8×25 mm.

SNRs of two active antenna designs: Inverted V vs horizontal dipole

2017-07-22T17:12:56+03:00

We present the results of numerical analysis of two design versions of active antenna which were considered for using in phased antenna array of GURT radio telescope at the stage of preliminary design. Both antenna versions are supplied with the same preamplifier but their dipole shapes differ. The first active antenna version has linear horizontal dipole, the second one — inverted V-dipole. The differences of input impedances, efficiencies, and mismatch coefficients of dipoles with preamplifier as well as the effect of these parameters on noise temperatures and SNR of antennas are analyzed in detail.

Active antenna with switchable beams for wireless sensor networks and IoT

2017-07-22T17:12:57+03:00

An active antenna capable of changing the beamwidth and pointing direction of its main radiating beam is presented. The design exploits the use of a novel frequency selective surface (FSS) and variable capacitance diodes (varactors) to control the main beam of an antenna. The main beam azimuthal pointing direction can be steered ±18° from boresight and the −3dB beamwidth varied from 100° to 140°. Narrower beamwidths can be achieved by changing the size and shape of the active ground plane. The design is suitable for applications where even small changes to the antenna parameters (gain, beamwidth and pointing direction) can have a positive impact on coverage and performance. Operating within the 2.4GHz ISM band, the proposed antenna design is suitable for adaptive indoor WiFi networks, dynamic wireless sensor networks and the internet of things.

Large current radiator for long range GPR applications

2017-07-22T17:13:01+03:00

Some aspects of the Large Current Radiator construction for subsurface sounding applications at the depths of up to some hundred meters are considered. The antenna has to operate in a wide frequency band and transmit power effectively under the ground surface. It is shown that the antenna designed as a small horizontal magnetic loop with specific shape located close to the earth surface transmits power quite effectively when one of the wires, situated close the surface, is flat and the second is shielded by an envelope with certain electrical constants.

Study of perturbing factors effect on the performance data of antennas focused in the near-field zone for microwave application problems

2017-07-22T17:13:03+03:00

Problems of the estimate of the eifect of random errors on the characteristics of the electromagnetic field focusing in the radiating near-field region in dissipative medium are studied. Quantitative estimates of the errors effect of the aperture distribution on the parameters of the focusing electromagnetic field are obtained.

Using of printed antennas to evaluate the permittivity of materials

2017-07-22T17:13:05+03:00

The paper considers the results of modeling the calibration dependence for the dielectric permittivity sensor in the form of a patch antenna in a contact measurement method. The problem is solved by a numerical method in the FEKO simulation environment.

Investigation of the electrodynamic characteristics of fractal double-ring antenna

2017-07-22T17:13:06+03:00

The electrodynamic parameters of fractal double-ring antennas are presented in the article. The design of these antennas is based on the topology of circular fractal lakes. The frequency dependences of the input impedance, the standing wave coefficient, and the directional properties of two-ring antennas are calculated and analyzed. Calculations of the characteristics, produced by numerical simulation, allow one to see the influence of the scale factor of the rings on the broadband characteristics of the antennas.

Microwave irradiator in the form of a piece of rectangular waveguide with dielectric insertion and narrow slot

2017-07-22T17:13:08+03:00

The microwave irradiator in the form of a piece of a rectangular waveguide with a dielectric insert inside and a narrow slot in the end wall was experimentally investigated. The irradiated object is located near the slot in the outer region. It is shown that with the help of a dielectric insert it is possible to practically completely match this system, which ensures a high efficiency of irradiation of fragments of a material medium or dielectric samples of finite dimensions.

Characteristics of directivity of vibrator antennas placed parallel to flat screen

2017-07-22T17:13:10+03:00

The directivity diagrams of the Hertz dipole and a half-wave vibrator, which are situated parallel to the plane perfectly conducting infinite screen, are determined in the entire front half-space. It is shown that the width of the main lobe of the directivity pattern is increased when the radiator height above the screen is increased. After comparison with the known results it is proved that the calculation of the coefficient of directivity, which was obtained by integrating the directivity pattern over the entire space, made it possible to provide high accuracy of the calculation. It is also shown that the maximum of the coefficient of directivity of the Hertz dipole and the half-wave vibrator above the screen in the direction of the normal to the screen is equal to four times of the coefficient of directivity of these radiators in the free space.

Microstrip antenna with complex configuration of radiators

2017-07-22T17:13:11+03:00

The results of investigations of complicated structures, which are microstrip objects with complex configuration of discontinuities are presented. The influences of internal parameters on integral characteristics are studied. The spectral characteristics, matching characteristics with external circuits, the pattern characteristics are presented.

Miniaturized broadband printed unidirectional antenna with parasitic slots for indoor wireless applications

2017-07-22T17:13:13+03:00

In nowadays communication systems, the size and performance of antennas are simultaneously required, since there is a tremendous demand for an ultra-wideband, compact and efficient antenna structures that may perform at all desired sub-bands starting from LTE (780 MHz) up to WiMAX applications (5.5 GHz) with a good level of radiation efficiency and dimensions not exceeding 130∗100∗10 mm. All these features are hard to achieve simultaneously. Therefore, for the sake of satisfying these demands, it has been suggested in this study to add parasitic slots to the printed Quasi-Yagi antenna, where by modifying their shapes, sizes and positions within the antenna, a significant performance is obviously detected. Simulation results using CST software suite have shown a clear enhancement in the bandwidth (6:1), and radiation efficiency (Gain = 5dB on average) with a very compact antenna structure allowing it to compete with the well-known antenna systems provided by international antenna companies like KATHREIN and TAOGLASS etc. Results are based on CST simulations and practical measurements.

Modeling microstrip antennas for UHF RFID tags

2017-07-22T17:13:16+03:00

Several design options of UHF microstrip antennas useful in RFID tags are proposed. This study shows antenna characteristics of the tags and the simulations results of reading range of tags, which are accordance with European and North American standards of the reader radiation power.

Methods for calculating electrically small wire antennas

2017-09-05T17:54:20+03:00

The optimization method for the electrically small linear wire antennas with lumped reactive loads included to their branches is first proposed. The results of the analysis and optimization of microwave characteristics of electrically small linear wire antennas with reactive loads are presented. The results for the quality factor and efficiency of such antennas are first presented. The study is carried out by the approximate and rigorous methods.

Two-band circular polarization antenna for Argos-3

2017-08-14T17:23:14+03:00

The article deals with an two-band circular polarization antenna for the marine terminal satellite communications system Argos-3. Satellite communication system Argos-3 is designed to collect meteorological and oceanographic information and determine the coordinates of moving objects. The antenna consists of two patches, which are located one above the other and flat screen. With the aim of forming a circular polarization the top patch has a pair of truncated square corners, and the bottom patch has a pair of truncated isosceles triangular corners. Antenna model was created in CAD FEKO. The main characteristic of the model was calculated in the program. The antenna prototype was created and its characteristics were measured.

Optimization of circularly polarized radiation of in-phase crossed impedance dipoles with screen

2017-07-22T17:13:21+03:00

The necessary conditions which provide the circularly polarized radiation with maximum directive gain for the in-phase crossed impedance wire dipoles system located over a perfectly conducting square screen have been investigated in the normal direction to the screen. On the base of the uniform geometric diffraction theory method with using the asymptotical expression for a current of an impedance wire dipole located over an infinite perfectly conducting plane the fast active 3D algorithms have been developed. The appropriate distributed surface impedances of the in-phase crossed dipoles have been defined taking into account the diffraction effects on the screen edges. The detailed analysis of the surface impedance values, the radiation resistance and directive gain depending on the screen's sizes and the dipole removal from the screen is given.