Vol 22, No 4 (2019)

This article is devoted to the development of correct methods for electrodynamic analysis of single and multi-element radiating structures with substrates of chiral metamaterials. An approach to the electrodynamic analysis of such antennas based on the method of singular integral representations of the field and the method of surface impedances is proposed. A system of singular integral equations with respect to unknown distribution functions of current density over emitters is obtained. The proposed method was tested using the example of solving a test problem using the Feko software package. The prospects of using such ICs in MIMO systems are shown, which make it possible to increase their efficiency, in particular, to increase throughput. The effect of azimuthal scattering of electromagnetic waves is also presented, which can be used to create low-profile antennas of subscriber radio communication stations installed on mobile objects.

The program of electromagnetic modeling antenna arrays HF-range has been developed to eliminate the shortcomings and limitations of the existing programs of analysis and synthesis of wire antennas. The technique assuming the numerical solution of systems singular integral equations of Pocklington type in approximation of a projection method Galerkin forms a basis of the software. Decomposition of unknown current density functions in the basis of piecewise linear functions is performed. The generated software solution made it possible to implement computational procedures in the near-real-time mode without imposing restrictions on the size and number of elements in the analyzed antenna array when parallelizing computational processes with numerical integration on the CPU. To demonstrate the functionality of the program, examples of modeling a wire Z-shaped antenna array are given.

In this paper the single biconical ultra-wideband reception device which is a part of directional-finding array is considered. Directional characteristics and matching of this device well-known and this characteristics can be improvement in several ways, for example, by means of the dielectric lens. However, use of classical lens essentially increments the terminating dimension of a device and all system. In this paper methods of transformation of the shape of a radiation pattern by means of the different dielectric insert in interior volume of receptions device are described. Directional characteristics and matching of a reception element will be defined by shape and dielectric properties of an insert.

A new approach to constructing the elemental base of electronics in the microwave and terahertz ranges associated with the development of functional elements of radio electronics based on Bragg structures have been proposed. The possibility of creating narrow-band rejection filters based on Bragg structures with a frequency-independent transmission coefficient close to unity outside the stop band has been demonstrated. The characteristics of small-sized matched loads for operation in the microwave and terahertz frequency ranges based on Bragg structures containing nanometer metal films have been described. The possibility of using microwave photonic crystals as a new types of electrodynamic systems for measuring the parameters of materials and structures by microwave methods has been considered. The coaxial photonic crystal was used for implementing the method for measuring the complex permittivity of dielectrics, based on the use of the transmission and reflection frequency dependences at the frequency of the defect mode in the band gap.

The work explores the possibility of using the acousto-optical effect to demodulate a sequence of radio pulses. Measuring setup circuits for determining sequence parameters are proposed. The methods for analyzing the diffraction pattern that relate the intensity distribution to the signal characteristics are described. Experimental and theoretical curves are constructed. Based on the data obtained, a conclusion is made regarding the requirements for the materials of crystals which is the main part of acousto-optic cells. The conditions for the appearance of uncertainty regions are described.

A review of the main scientific results on creation of new information technologies on the basis of textures, fractals, fractional operators and non-linear dynamic methods which were obtained by the author has been presented in this work. The researchers are conducted in the framework of scientific direction «Fractal radio physics and fractal radio electronics: designing of fractal radio systems» which is being developed by the author starting from 1979 and up to the present. It is shown that new dimensional and topological (not energy!) signs or invariants that are combined under the generalized concept of «Sampling topology» ~ «Fractal signature» were proposed for the first time and then applied. Texture and fractal-scaling (topological) methods for detecting superweak signals and fields in intense noise and interferences are proposed. A new type and a new method of modern radiolocation, namely, fractal-scaling or scale-invariant radiolocation was proposed, discovered, and developed. This entails fundamental changes in the structure of theoretical radiolocation, as well as in its mathematical apparatus. The fractal radiolocation postulates were developed: (1) intelligent signal/image processing based on the theory of fractional measures and scaling effects for calculating the field of fractal dimensions D, (2) the sample of the received signal in noise belongs to the class of stable non-Gaussian probability distributions of the D signal, and (3) the topology maximum with the minimal energy of the input random signal (i.e., the maximal «escape» from the energy of the received signal). These postulates open new possibilities for ensuring stable operation at a small signal/(noise + interference) ratio or an increase in the radar range. These studies are priorities in the world and serve as a basis for the further development and substantiation of the practical application of fractal-scaling and texture methods in modern radiophysics, radio-electronic systems, and nanotechnology, as well as in the creation of fundamentally new and more accurate fractal-texture (topological) methods for detecting and measuring the parameters of radio signals in the space–time radar channel for electromagnetic wave propagation with scattering.

The paper presents an approximate analytical solution in closed form for the mode of a weakly guiding circular optical fiber with an arbitrary profile of the refractive index. The solution is valid for guided linearly polarized modes of arbitrary radial and azimuthal orders. The proposed solution is based on the joint application of the Gaussian approximation method and the stratification method, as well as the replacement of an optical fiber with a bending radius significantly exceeding the radius of the fiber, some direct optical fiber with an equivalent profile of the refractive index. The results of calculations for a typical refractive index profile of a multimode optical fiber with a core and cladding diameters of 50/125 are presented. It is shown that for the considered examples, the degree of influence of the bending radius on the propagation constant of the mode of a curved fiber waveguide increases with increasing mode order. And, in the range of changes in the bend radius of the fiber, in which the conditions for applying the proposed approximate analytical solution are fulfilled, the mode propagation constant due to the bending of the fiber changes insignificantly and we can assume that this change does not depend on the value of the bend radius.

The article considers the class of periodic systems in waveguide devices of the microwave frequency (microwave) range of electromagnetic waves, which show the effects of Bragg resonance reflection in this frequency range. The priority areas of using these structures in the field of measuring the electrophysical parameters of materials and substances are shown. The general principles of the operation of measuring instruments for controlling the dielectric parameters of liquid media based on sensitive elements in the form of Bragg microwave structures implemented in a coaxial waveguide are formulated.

The article proposes the principle of converting a chirped pulse signal into an amplitude-modulated signal (within each information pulse) based on a fiber-optic erbium amplifier. The possibility of using traditional EDFA for this task is analyzed. The parameters of the erbium medium of the amplifier providing the indicated conversion are found. The parameters of the converter have been evaluated.

The article is devoted to the development and research of distributed fiber systems for aeroacoustic control of gas-air flow parameters on the nozzle section of turbomachines. The problem of source localization and restoration of the acoustic field of turbomachines is considered. The control of the aeroacoustic control system based on fiber-optic sensors based on the principles of self-learning is considered, since extreme controllers, although simply technically implemented, but have low speed, which is especially affected with a large number of control elements. Therefore, the aeroacoustic fiber-optic complex will be considered in the form of an automatic control system with the adaptation of the parameters of the mathematical model by the measured values of the flow parameters that change with the change of the

Solutions for a multi-sensor catheter in high resolution manometry based on classical interrogation with wave separation of fiber optic sensors or their polyharmonic probing already exist. Measuring systems based on interrogating arrays of the same type of Bragg gratings by the method of interference with a frequency shift and spatial separation of obtaining information from each grating separately, although their spatial resolution is slightly lower than required, are proposed. The indicated type of solutions requires expensive tunable lasers or narrow-band filters, and frequency-shifted interference, including two-frequency, with a microwave photonic interrogation method, entails the construction of an extremely complex interferometric optoelectronic circuit with the need to ensure its stable operation. Supplementing the task with the requirement to simplify and reduce the cost of the system as much as possible by means of microwave photonic sensing methods and using an array of structured gratings or gratings with phase shift in the system, and, finally, addressable fiber Bragg gratings, which we are actively developing, we will get a complete statement of the problem of constructing a multi-sensor catheter for intestinal manometry. The results of these task solutions are presented in this article.

An algorithm for detecting cardiac arrhythmias which based on spectral analysis of the electrocardiosignal is presented. Signals of bigeminy, trigeminy and paroxysmal supraventricular tachycardia were taken for analysis. A coefficient depending on the boundary frequency which displays the differences in the signal spectra is introduced. The boundary frequency at which the total error probability is minimal is found. The thresholds of decision-making at the found boundary frequency are determined.

The article presents a method of phase-frequency spectral analysis of an electrocardiogram signal for use in portable arrhythmia detectors. The selection of spectrum values for differentiating between normal and abnormal QRS complexes of the electrocardiogram signal is describe. Sample spectra for various QRS complexes of real life signals are given. We developed an algorithm for detecting arrhythmias and further distinguishing them. The results that was obtained by spectral analysis should be used to prevent the development dangerous type of arrhythmias and their timely exposure detection.