Vol 21, No 3 (2018)

The possibility of simultaneous determination of parameters from the temperature dependence of the reflection spectrum of microwave (microwave) radiation for magnetic fluids and silicon. The dielectric constant, the volume fraction of the solid phase, the tangent of the dielectric loss angle, and the diameter of the magnetic fluid particles, and the thickness silicon sample, conductivity , effective mass, the activation energy and concentration boron in silicon are determined. It is shown that taking into account the dimensions and spatial arrangement of agglomerates from magnetite nanoparticles for magnetic fluids and temperature dependence concentration and mobility under the influence of two mechanisms of dispersion leads to an increase in the accuracy in determining the required parameters.

In this work the peak-factor decreasing method for the OFDM systems is proposed, based on the group spectrum subcarriers processing and the signal constellation rotation. Such parameters of the OFDM system as the instantaneous value of the peak-factor, the bit error probability of the receiving signal, the selective (empirical) distribution function of the peak-factor values depending on the precoding functions are estimated. An experimental research confirming the effectiveness of the proposed method was carried out. Theoretical work significance consists in discrete functions using for precoding and simultaneous signal conversion on each subcarrier. Practical novelty consists in the possibility of using the developed method of reducing the peak factor in the DVB-T2 standard digital television systems. The application of the proposed method will make possible the fully use of the power amplifiers operation range and to avoid nonlinear signal distortions. The receiving BER level will decreased by the signal constellation rotation to the recommended angle for the given modulation type.

The main features of the application of the barycentric method in the numerical solution internal problem of electrodynamics with the allocation of the limitations of the method and its main stages are considered in the article. Methods for finding harmonic barycentric coordinates for a single-connected homogeneous analysis domain with a piecewise linear boundary are presented. In order to provide clarity and determine the preference for the use of barycentric method, the algorithm for solving the internal problem of electrodynamics of a mirror antenna, including one source of the electromagnetic field (irradiator) and a reflector is presented. Examples of numerical calculation of the current density on the reflector surface by the barycentric method depending on the order of approximation are given. Advantages and disadvantages of the barycentric method are highlighted.

In the present paper, we investigate the possibilities of reducing the distortions of propagated in optical fibers high-power femtosecond pulses due to the choice of its refractive index profile, taking into account the profile changes due to the cubic nonlinearity of the material of lightguide. Approximate analytical expressions are presented for calculating the dispersion characteristics of an optical fiber with an arbitrary profile of the refractive index. This analytical exspressios take into account the profile changes due to the Kerr nonlinearity. A technique for synthesizing a profile optimized for transmission of optical pulses with given parameters is proposed. An example of a synthesized profile is presented. The results of simulation the propagation of optical pulses in the step-index optical fiber and in the fiber with a synthesized profile are presented.

The review of the existing researches to the analysis and synthesis of antennas on the basis of metamaterials, and also a number of new researches of authors on possibilities of application of chiral metamaterials in antenna equipment and networks of radio communication is given. The prospects of using metamaterials in antenna systems of radio communication networks in order to improve their electrical and mass-dimensional characteristics are substantiated.

The self-consistent problem of electromagnetism is defined as a closed mathematical cycle in which the primary sources of the electromagnetic field are corrected by the inverse effect of secondary sources arising from them as a result of the interaction of the radiation field with the surrounding medium. In a stationary state such a cycle is described by a homogeneous boundary value problem either on the differential, or integral, or integro-differential equations, that is, the eigenfunction and eigenvalue problem. Four most widespread variants of self-consistent boundary value problems are formulated.

Microwave photonic sensor systems represent a wide class of information systems with measurement conversion that use standardized analog and parallel links of parallel and sequential type with filtering, allowing to functionally displaying the information of the measurement conversion, obtained in the optical range, in the radio frequency one. One of the main, most widely used elements in the microwave photonic sensor systems, which solves the problems of forming, filtering and measuring the conversion of optical radiation, including for the stage of further generation of radio-frequency carriers, is the fiber Bragg grating. The cumulative analysis made it possible to propose for the design of microwave photonic sensor systems a new class of sensors - address fiber Bragg structures - constructed on the basis of the fiber Bragg grating with two symmetrical discrete phase shifts or two identical the fiber Bragg grating, potentially having improved metrological and technical and economic characteristics. Of particular interest are few-sensor measurement systems designed to simultaneously measure two related physical quantities simultaneously. In this paper, we will consider a mathematical model of a combined complex fiber-optic temperature and pressure sensor, as an example of constructing few-sensor microwave photonic measuring systems, which, without loss of generality, can be extended to temperature-deformation, temperature-strain pairs, etc. Discussed and resolved the problems of measurement situations, the emergence of which is determined by the essence of the address approach, and are aimed at unambiguous determination of the characteristics of the fiber Bragg grating with unic address.

Creation of non-linear radio engineering systems is the perspective direction. In radio engineering system as informational chaotic fluctuation is used. In work non-linear filtration of mix of chaotic fluctuation and noise is investigated. The non-linear filter contains the bistable system - Schmitt’s trigger and the edge filter. In the filter the effect of a stochastic resonance takes place. The signal at the exit of non-linear system amplifies with body height of intensity of noise to some of its best value. For narrow-band signals the effect of a stochastic resonance is investigated rather explicitly. Results of model operation are given in the Multisim program.

In work the algorithm of modeling in the environment of Ansys HFSS of the hybrid ring bridge of range of operating frequencies D1 is stated. Electric characteristics of model are received. By results of modeling the experimental sample of the hybrid ring bridge is created.