Radio physics and electronics

8-13

Authors: A. V. Brovenko, P. N. Melezhik, A. Ye. Poyedinchuk, O. S. Troshchylo

Development and design of the frequency multipliers and other devices based on nonlinear dielectrics require a study of their electrodynamic properties. For this purpose, the problems of the electromagnetic wave diffraction on various structures containing nonlinear dielectrics have to be solved. In this paper we consider the problem of diffraction of a plane linearly polarized electromagnetic wave on a nonlinear dielectric layer ,whose nonlinearity is described by the Kerr law. An effective algorithm for this problem solving is implemented on the basis of construction of the special solutions of the Cauchy problem for the nonlinear Riccati equation. The numerical results for the considered nonlinear structure are presented. The ranges of amplitude and frequency of incident electromagnetic wave in which hysteresis appears in the reflection and transmission coefficients dependencies are determined. It is shown that selecting certain magnitudes of the incident wave amplitude enables wave reflectionless tunneling through a nonlinear dielectric. The results of the numerical experiment obtained in the work, besides their use for the development and design of electrodynamic devices containing nonlinear dielectrics, can also be used as "reference" ones in the study of diffraction processes in nonlinear dielectric structures, where the nonlinearity is characterized by laws different from the Kerr law, as well as for nonlinear dielectric structures of more complex geometry.

23-32

Authors: A. M. Linkova

Measurement of precipitation amount is of great inte-rest for solution of many practical problems of national economy and agriculture. In this case, the inverse problem of recovering the rain intensity using radar methods is an incorrect problem of mathe-matical physics and is described by a nonlinear integral equation. An approach for solving the integral equation of the electromagnetic waves scattering by a polydisperse medium of water drops is considered by means of double frequency remote sensing in the microwave range. Numerical simulation for retrieval of rain intensity in the range of 1…30 mm/h is performed for operating wavelengths 0.82 and 3.2 cm. It is shown that the proposed approach permits to retrieve the rain intensity with an error less than 20 % for intensities > 5 mm/h and with an error up to 60 % for light rains (less than 5 mm/h).

37-46

Authors: S. V. Kolosov, A. A. Kuraev, I. E. Zaitseva

The article describes a new type electronic device - gyroton on a corrugated resonator. In this device there is no spatial grouping of the electron beam, but it is possible to achieve a high conversion factor of the power of the electron beam into the power of the electromagnetic rotating wave. Straight-line at the input of the device, the electron beam gives its longitudinal energy to the same wave with an efficiency of more than 80 % due to its initial deviation from the axis of the slowed down TM11-wave. The me-thod described in the article reduces the 3D-problem to the 1D-problem, which increases the speed and accuracy of the solution of the boundary value problem. The developed mathematical model is the basis for a computer program for calculating and optimizing the interaction of relativistic electron flows with the fields of irregular round waveguides Gyro-K, which is a part of the software complex KEDR. The developed mathematical model of interaction processes of the relativistic electron beam with the fields of irregular circular waveguides and resonators makes it possible to carry out a theoretical analysis of the operation of a gyrotron generator with a corrugated resonator. As a result, the article demonstrated the possibility of providing an electronic efficiency of more than 80% and an output power of up to 30 MW for the developed gyroton mathematical model on a corrugated resonator.

58-80

Authors: M.I. Dzyubenko, Y.E.Kamenev, V.P.Radionov

The terahertz (THz) frequency range now attracts much attention of researchers and consumers in connection with many possibilities of using it for solving a number of practical problems in science, technology and medicine. Therefore, the development of new sources of radiation and the improvement of the existing ones are actual. The results of experimental and theoretical studies of gas-discharge THz-lasers, and numerous studies of the features of their work have been summarized in the paper. A number of new developments aimed at increasing the efficiency and expanding the functionality of gas-discharge terahertz lasers have been presented. New methods of pumping gas-discharge lasers, which were developed, have been presented. We have proposed new technical solutions which allow increasing the power and efficiency of the laser by optimizing the synthesis of the active substance and eliminating the negative impact of synthesis by-products. New methods for modeling the shape of laser pulses in lasers pumped with pulsed current and alternating low-frequency current have been presented. New types of laser resonators and new varieties of mirrors have been proposed and created and they have been presented in this work. Laser resonators with mirrors that do not require accurate alignment have been developed. Partially transparent mirrors, in the form of flat periodic structures that combine the functions of concave mirrors and focusing lenses, have been proposed. These mirrors can reduce the diffraction loss of laser radiation. Resonators with new principles of smooth regulation of radiation output from them, have been presented. Multifrequency lasers have been developed. Systems for the smooth adjustment of the frequency of electromagnetic laser radiation, in which adjustment is carried out without the use of frequency measuring equipment, have been designed for these lasers. All these new developments, presented here, have made it possible to improve the parameters of terahertz lasers and to expand their field of application. Some applications of THz lasers, in particular medical applications and in the field of measurement have been presented. New ways of measuring the refractive indices of various substances and materials in the THz range, using the developed lasers, have also been presented in this work.