Introduction. Adaptive statistical prediction of a random process is relevant to a noise compensation in radar and optical location problems. The shape of the signal reflected from the target is often unknown due to the use of short probing pulses passing during their duration in a distance less than the size of the target. Subtracting the noise forecasted in the previous time point from its current value allows one to compensate for the noise.

Aim. Investigation of the problem of adaptive linear prediction of random processes by a non - recursive linear filter implementing a sequential regression algorithm for infinitely and finitely differentiable random processes.

Materials and methods. Models of random interferences in the form of infinitely and finitely differentiable random processes were considered. The sequential regression algorithm required to estimate the correlation selection matrix, the selection vector of correlation of the forecast and sample units. Due to random process and its derivative incorrelation, the sparse correlation selection matrix was formed. This factor reduced the number of mathematical operations.

Results. The results of numerical calculations and the implementation of random process, its optimal and adaptive prediction obtained during the simulation were presented. The adaptive predictive filter with random process derivative sampling provided at least a one third reduction of the number of mathematical operations in comparison with the transversal predictive filter.

Conclusion. An algorithm of sequential regression in predicting a random process and its a priori unknown parameters is the closest to the ideal algorithm of direct matrix inversion. It allows to adapt to the changing process parameters. The number of iterations in non-recursive filtering and the value of attenuation of the estimated linear regression coefficients during the adaptation can be used to adapt to the changes in the parameters of the predicted process.

Introduction. Measurement systems for research of telecommunication devices and of their elements are difficult to maintain and expensive. Therefore when possible, its may be replaced by virtual measurement systems (VMS), which allow one to perform measurements based on physical parameters of testing device.

Aim. VMS development for measuring of amplifiers parameters by means of simulation modeling based on amplifier topology.

Methods and materials. VMS is to be used for research of a small signal amplifier (a part of transceiver). It consists of program modules and graphic interface, realized by LabVIEW. The program part contains text modules in LabVIEW syntax, which calculate S-parameters frequency dependencies for an amplifier. For definition of parameters amplifier circuit by a decomposition technique is being split into sequential two-port net-works, which can be described by corresponding matrixes. After determination of frequency dependent matrixes elements, the matrixes are being converted and multiplied. It allows one to obtain frequency dependencies of parameters of an amplifier. VMS interface is a 3-D-rendered on a computer screen front panel of a virtual vector network analyzer with a device under test connected to its test ports.

Results. VMS for UHF-amplifiers research based on given topology was described. The calculations of amplifier transmission lines and amplifier in the whole parameters based on corresponding matrixes and their conversions were presented. The algorithm of a measuring system operation was described. 3D measuring complex and objects under test visualization were shown. The comparison with existing software for design and simulation of UHF-devices such as Microwave Office was realized.

Conclusions. Contrary to Microwave Office, aimed to solution of synthesis tasks, VMS is aimed to research tasks. It has a realistic visualization of measurement devises and simple parameters input, do not need big computer resources and is free. VMS can be used in educational process, especially for online education, when using of Microwave Office is impossible.

Introduction. Remote monitoring of layered underlying surfaces is an urgent task. To assess the performance of new algorithms for processing the radar signal reflected from the surfaces, full-scale tests are required. As their carrying out demands big expenses, simulation modeling is actual. There are many methods of estimating an electromagnetic field (EMF) scattered by the earth's surface. However, there are no proven methods and algorithms for engineering calculation of the reflected radio signal in the conditions of this problem.

Aim. The aim is to develop and to verify a software model to simulate the reflected multilayer extended structure of the radio signal received on board the aircraft.

Materials and methods. The core of the model was based on high-frequency electrodynamics' methods, which allowed rapid calculation for large areas of targets with any number of layers. Simulation was produced using the MATLAB software package. The developed simulation model represented the result in the form of the normalized radar cross-section (RCS) of the multilayer structure. Since the layered structure had rough boundaries, the model provided triangulation of the boundaries of the volume-distributed object. The resulting EMF was calculated using the superposition principle. Each partial EMF value on the facet was calculated taking into account the phase and the polarization of the locally incident EMF.

Results. In the paper the comparison of simulation results with theoretical calculations for the normalized RCS of a two-layer structure (difference is less than 10 percent) was presented. Verification for the coefficient of variation of the envelope of the reflected radio signal from the depth of groundwater (critical error was 7 percent) was performed. RCS modeling of the absorbing layer with different degrees of roughness of the layer boundaries was carried out. The upper boundary roughness (for maximal height deviation 0.1 m) affected on specific EPR more than lower boundary. It manifested itself in decreasing of RCS down to 30 dB.

Conclusion. The developed model is intended to reduce expenses for designing synthesis of subsurface imaging systems with comparison of scheme "model of device development – field tests – completion – etc". The model is designed to verify the new signal processing algorithms for subsurface radar. 

Introduction. A conversion of thermal energy into electrical energy is an urgent task. The thermovoltaic effect (TVE) found in samarium sulfide (SmS ) makes it possible to solve a higher efficiency problem as compared with classical thermoelectric generators operating on the basis of the Seebeck effect. TVE in SmS, is manifested in an appearance of voltage pulses of 0.05 V in continuous mode when a sample is heated to 470 K. Generation of electromotive force (EMF) is associated with a presence of a concentration gradient of defective Sm ions in sulfur sublattice vacancies, with a change in their valence (Sm²⁺ ® Sm³⁺+e^-) and with electronic Mott transitions. TVE discovered subsequently in ZnO, Ge, Si, and in some complex semiconductors, reached only 0.01 V.

Aim. To increase the magnitude of the generated voltage and the operating temperature at TVE.

Methods and materials. By the method of synthesis from simple substances, raw materials were obtained from which SmS/Sm_1-xLn_xS sandwich-type heterostructures were created, where Ln = Eu, Yb. In addition, samples based on a classical thermoelectric PbTe with different degrees of doping of the layers obtained by pressing at high temperature in a vacuum were investigated. On the unique equipment, excluding temperature gradients in samples, TVE was studied.

Results. It was shown that an increase in the EMF value and in the operating temperature had been achieved due to the penetration of donor levels by doping. In doped samples on the basis of SmS, a generation of EMF up to 0.15 V was observed in continuous mode at T = 700 K. TVE detected in the n-type thermoelectric semiconductor heterostructure PbTe, make it possible to obtain the magnitude of the generated voltage of near 0.06 V in the medium temperature mode.

Conclusion. The achieved results exceed the previously known ones and give grounds to continue research with the aim of developing semiconductor converters operating on the basis of TVE.

Introduction. The advent of spin oriented electronics, or spintronics, in the late 1980ies has not only revolutionised the very idea of contemporary electronics but has also brought about a major technological breakthrough in the field of information storage and processing. Further progress is associated with the rapidly emerging field of spinorbitronics seeking to put to maximum use the SOC (Spin-Orbit Coupling) related phenomena.

Aim. The purpose of this review paper is to outline the major trends in the dynamically developing field of spinorbitronics in the context of evolution of the mainstream spintronics. SOC related effects open up the possibility of creation of a new generation of energy saving devices, a key challenge in electronics in general.

Materials and methods. A special effort has been undertaken to make the article appealing to the general reader, especially to specialists in the field of radioelectronics and data processing. To this end, in the description of the complex physics underlying magnetic interactions preference is given to simple term "naive" interpretations.

Results. Apart from the analysis of the fundamental features peculiar to the interfaces between ultrathin films of ferromagnetic and heavy metals and related to strong SOC, we discuss specific configurations especially promising for application-oriented research. Among others, these include spin torque microwave (1...50 GHz) oscillators, fast domain walls in racetrack memory and especially magnetic skyrmions.

Conclusion. Publication of this paper will facilitate creative interaction between the fundamental and applied research, thus contributing to the development of novel high-performance spintronic devices.

Introduction. The distinctive feature of a coplanar transmission line with thin ferrite and ferroelectric films is the absence of undesirable irregularities in dispersion for relatively low frequencies when the wavelength approaches the thickness of ferroelectric layer, in contrast to the open ferrite-ferroelectric wave-guiding structure without metallization.

Aim. The purpose of this paper is twofold: (i) to develop a theory of the wave spectra in the multiferroic structures based on the coplanar lines; (ii) using this theory to find ways to enhance the electric tuning range.

Materials and methods. The dispersion relation for spin-electromagnetic waves was derived through analytical solution of the full set of the Maxwell's equations utilizing a method of approximate boundary conditions.

Results. A theory of spin-electromagnetic wave spectrum has been developed for the thin-film ferrite-ferroelectric structure based on a coplanar transmission line. According to this theory, dispersion characteristics of the spin-electromagnetic waves were described and analyzed for different parameters of the structure. The obtained results show that the investigated structure demonstrates a dual electric and magnetic field tunability of wave spectra. Its efficiency increases with an increase in the thicknesses of the ferrite and ferroelectric films and with a decrease in the width of the central metal strip.

Conclusion. The distinctive features of the proposed coplanar waveguides are the thin-film planar topology and dual tunability of the wave spectra. All these advantages make the proposed structures perspective for development of new microwave devices.

Introduction. Coupled two- or three-wire microstrip lines are often used to reduce a phase noise of voltage-controlled oscillators (VCOs). Unfortunately, the phase noise was not optimized depending on the lengths of a three-wire coupled microstrip lines.

Aim. For the three-wire coupled microstrip structure, the task of determining of the optimal lengths of its stabs was set. The stabs were corresponded to the reduced phase noise of the selected VCO.

Materials and methods. In the oscillator example, the resonator model with three electromagnetically coupled microstrip lines was studied. Herein the second line from the first and the third from the second line differed by the same physical length. The widths of the first and of the third lines were the same, and their coupling clearances with the second line were the same too. On the one hand, in this three-wire microstrip line short-end modes with a common ground electrode were implemented. On the other, at the ends of the first and of the third lines open-end modes were implemented. The free end of the second line is line input.

Results. For the considered oscillator, the basic formulas for calculating its frequency-setting elements and resonator model parameters were obtained. By these formulas the estimation of base contours impedances for two oscillators with three-coupled microstrip lines of the same and different lengths, and also for the oscillator using a two-coupled microstrip line was given. For comparison, the proposed VCO near the optimal difference in the three-wire line microstrips lengths had the base contour impedance phase steepness 2...4 times greater, as well as its modules graphs had the width 4...10 times less.

Conclusion. In comparison with the known VCOs, the possibility of obtaining lower phase noise spectrum levels at 6...10 dB/Hz in the designed oscillator with the calculated lengths of the selected three-coupled line microstrips was experimentally confirmed.

Introduction. Currently, sheet metal is the main structural material for multi-purpose use. The actual task of the industry is to improve the quality of rolled sheet. It allows to ensure the necessary reliability of structures and products of especially critical use. The regulatory documents currently in force allow an ultrasonic testing of sheet metal by reflection or by transmission method. Due to lack of specific recommendations it becomes unclear which of the methods is preferable to use.

Aim. An estimation of the maximum detectability of rolled sheet planar extended defects by reflection methods (echo method) and by transmission methods (shadow and mirror-shadow methods).

Materials and methods. Based on analysis of the equations of acoustic paths, formulas were determined. The formulas allow one to evaluate an ultimate detectability of planar discontinuities of plate rolling by echo, shadow and mirror-shadow methods in a contact version by longitudinal waves. Experimental studies were conducted under computer simulation using the Mathcad mathematical package.

Results. Integral expressions for calculating of amplitudes of echo signal from a plane defect, of bottom signal in defect-free and defective areas and their ratio for the echo method were obtained. The expressions for calculating of amplitudes of transmitted and bottom signals in defective and defect-free areas and their ratio for shadow and mirror-shadow methods were determined. Based on the numerical analysis, an estimation of the maximum detectability of planar extended defects of sheet metal was realized. It is possible to detect defects with a thickness of 5 pm by reflection methods and with a thickness more than 100 pm by transmission methods.

Conclusion. It was established that reflection methods have better capabilities for detecting plane defects by longitudinal waves. The conditions for reducing of the thickness of the equivalent layer associated with an increase in transducers wave size were determined. It was shown that in order to detect defects with a small thickness, it is more expedient to give preference to the echo method of ultrasonic testing.