Радиотехника и электроника

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Discrete Amplitude Noise Components of Amplifier Klistrons

Fri, 05/01/2020 - 00:00

Abstract—The kinematic theory of discrete klystron noise associated with the rectified voltage ripple of power sources is presented. The results of the theory are compared with experimental data and recommendations on the choice of the ripple coefficient are given.

On the Effect of Transverse Thermal Velocities of Electrons in the Converging Sheet Electron Beams Formed by Guns with Partial Magnetic Shielding of a Cathode

Fri, 05/01/2020 - 00:00
Abstract

We report on the results of investigations of the effect of the initial thermal velocities of electrons in the converging sheet electron beams formed by guns with partial magnetic shielding of a cathode. The results are presented in the form of generalized dependences, which can be used to control the thermal beam configuration with different beam parameters and focusing magnetic fields and simulate the electron-optical systems that ensure a required current flow of such beams in the transit channel.

A Family of Optimal Window Functions for Spectral Analysis with the Spectrum Sidelobe Falloff Rate Multiple of 12 dB per Octave

Fri, 05/01/2020 - 00:00
Abstract

A synthesis problem is solved for low-order windows with the sidelobe spectrum falloff rate equal to 12n decibel per octave (dB/oct), where n is an integer, that are optimal by the criterion of the minimum highest spectrum sidelobe level over a given frequency region outside the main lobe. To obtain this sidelobe falloff rate, it is proposed to synthesize the windows in the form of a portion of the Fourier series in terms of cosine functions with an odd number of half-waves along the observation interval. A synthesis method for the optimal functions with verification of the solution is developed. Order 3 to 6 windows with sidelobe falloff rates 12, 24, and 36 dB/oct are synthesized and their parameters are presented.

Double Stochastic Filtration of Spatially Inhomogeneous Images

Fri, 05/01/2020 - 00:00

Abstract—The representation of spatially inhomogeneous images using double stochastic autoregressive models is considered. The possibility of synthesizing semicausal double stochastic image filtering algorithms based on such models is shown. Variants for reducing the computational costs required to implement double stochastic filters using cascades of moving windows are considered. A comparative analysis of the proposed algorithms with well-known counterparts is carried out, confirming the practical possibility of using double stochastic filters for processing real two-dimensional images.

On the Possibility of Studying Ferrofluids by a Nuclear Magnetic Magnetometer with a Flowing Sample

Fri, 05/01/2020 - 00:00
Abstract

In this paper, we consider a new method that employs a highly sensitive nuclear magnetic magnetometer with flowing water to determine the magnetic susceptibility and Curie constant of magnetic fluids with an error no greater than 1.0%. The Curie law was shown to be fulfilled in the temperature range of 283–323 K, in which ferrofluidic cells are used. A further increase in the temperature of the ferromagnetic fluid leads to an insignificant change in the Curie constant. The results of experimental studies are presented.

Measurement of the Complex Dielectric Constant of Materials Based on a Ridge Waveguide

Fri, 05/01/2020 - 00:00

Abstract—The problem of determining the complex dielectric constant of materials in the centimeter and millimeter wavelength ranges is solved using the waveguide method with an double-ridged waveguide. The use of a segment of an double-ridged waveguide as the measuring cell made it possible to expand the operating frequency range and increase the measurement accuracy due to localization of the electromagnetic field energy in the space between metal ridges. The electromagnetic fields of hybrid types of waves in the double-ridged waveguide were calculated by the partial region method taking into account the peculiarities of the electromagnetic field on the metal and dielectric ridges. The results of measuring the complex dielectric constant for samples made of ebonite, Teflon, and fiberglass are presented.

Numerical Simulation of Very-Low-Frequency Waves Passing through the Magnetoactive Plane-Layered Plasma of Earth’s Lower Ionosphere

Fri, 05/01/2020 - 00:00

Abstract—The article describes an algorithm for calculating the characteristics of the passage of low-frequency electromagnetic waves through the magnetoactive plane-stratified lower ionosphere. The algorithm is based on numerical integration of wave equations for the case of a plane wave incident on the ionosphere from below, taking into account the plasma’s ionic composition. As an illustration, the basic characteristics of passage of waves in the 0.05–1 kHz frequency range are calculated. It is shown that the power transmission coefficient of these waves is quite large, ranging from 0.2–0.4 for most of the frequencies used. It is shown that in the daytime near a frequency of ~300 Hz, the transmission coefficient in the daytime has a maximum and is approximately double the nighttime values.

Scattering of a Plane Wave by a Cylinder with a Piecewise Analytical Form of the Section

Fri, 05/01/2020 - 00:00
Abstract

The problem of scattering of a plane electromagnetic wave by a perfectly conducting cylinder is considered. The cross-section of the cylinder is formed by straight lines and circular arcs. The problem is solved by the hybrid method combining the eigenfunction method, the method of successive diffractions, and the equivalence principle. The calculation results obtained by the hybrid method, the method of moments, and the Huygens—Fresnel—Kirchhoff method are compared.

Electromagnetic Exposure Study on a Human Located inside the Car Using the Method of Auxiliary Sources

Fri, 05/01/2020 - 00:00

Abstract—The article studies the effect of the electromagnetic field of wireless communications on a human inside a car in the frequency ranges of 450, 900, and 1800 MHz, corresponding to the operational range of police radios and modern mobile phones. A comparative analysis of the influence of the Earth’s surface under the car is presented. The results of numerical calculations using the Method of Auxiliary Sources show the presence of resonance phenomena and a high reactive field inside the car, which leads to an undesirable increase in the level of absorbed energy in human tissues.

Resource and Power Allocation for OFDM-Based Device-to-Device Communications in a Multicell Environment

Fri, 05/01/2020 - 00:00
Abstract

We investigate the optimal resource and power allocation for device-to-device (D2D) communications in a multicell environment. When D2D links reuse the cellular radio resources, each D2D user will interfere with a cellular link and other D2D links, in its own cell as well as in adjacent cells. We first develop a distributed resource allocation scheme that is performed by each base station independently. Then, we propose a coordinated resource allocation scheme that can handle the intercell interferences as well as the intracell interference. For a given resource allocation, we also formulate a power optimization problem and present an algorithm to find the optimal solution. The resource and power allocation algorithms are designed to maximize the achievable rate of the D2D link, while limiting the interference generated to the cellular link. The performance of the proposed algorithms is evaluated through simulations in a multicell environment. Numerical results are presented to verify the coordination gain in the resource and power allocation.

Synthesis of Electromagnetic Pulses with Different Frequency Bands in Free Space

Fri, 05/01/2020 - 00:00
Abstract

The synthesis of electromagnetic pulses with an extended spectrum is studied using summation of radiation pulses with different frequency bands in free space. The analytical estimation of the radiation spectrum with maximum width is performed for an array of combined antennas excited by bipolar pulses with durations of 0.5, 1, 2, and 3 ns. A combined antenna with an extended matching band is developed. The possibility to obtain ultrawideband radiation with a spectrum width of more than four octaves for an array of combined antennas excited by bipolar pulses with durations of 0.5, 1, 2, and 3 ns is experimentally demonstrated.

Lower Rao–Cramer Boundary of Variances for Parameter Joint Estimates of Narrowband and Broadband Signals Mixture with White Noise

Fri, 05/01/2020 - 00:00
Abstract

In this paper, we determine the joint estimates variance minimum of the signal parameters, a mixture of narrowband and wideband signals and white Gaussian noise that are presented as a complex total signal. An expression is obtained for calculating the Fisher matrix elements to establish the lower Rao–Cramer boundary. The dependences of the standard deviations (RMS) of the estimates on the signal-to-noise ratio, sample length, and on the initial signal parameters, such as the central frequencies of the signal components and the width of the broadband component, are presented. A comparison with the minimal standard deviations obtained for a signal model that includes only the broadband component is performed. Analysis of the results allows assessing the requirements that may be imposed on the developed algorithms for joint estimation of the mixture parameters of the considered signals depending on the set values of the sampling frequency and the sample size.

Application of a Microwave Coaxial Bragg Structure for the Measurement of Parameters of Insulators

Fri, 05/01/2020 - 00:00
Abstract

A method for the measurement of the complex permittivity of insulators using a microwave coaxial photonic crystal is proposed and implemented. The method is based on a solution to an inverse problem using minimization of the difference of experimental and calculated frequency dependences of the transmission and reflection coefficients at the defect-mode frequency in the band gap of a photonic microwave crystal containing a structure with the parameters that must be determined. An unambiguous solution to the inverse problem can be obtained using a defect mode in the band gap at the frequency of which a maximum of the standing wave is obtained in the region of the structure under study.

Change in the Field of Metaparticles for the Distribution of a Pulsed Wave Field Directionally Emitted by an Aperture Source

Wed, 04/01/2020 - 00:00

Abstract—The results of analyzing changes in the transverse size of the effective shape and radius of curvature of the phase wave front of a field of metaparticles during their directed propagation from the aperture source of a pulsed wave field are presented.

Method of Integral Equations for the Solution of Diffraction Problems about the Calculation of Twisted Guiding Structures

Wed, 04/01/2020 - 00:00
Abstract

The method of integral equations is suggested for calculating irregular twisted guided structures. The method is based on the Lorentz integral relationship and makes it possible to solve internal diffraction problems for waveguides, whose screening surface is described by analytical functions.

Mathematical Model of a Two-Element Microstrip Radiating Structure with a Chiral Metamaterial Substrate

Wed, 04/01/2020 - 00:00

Abstract—A mathematical model of a two-element array is presented, the substrate of which is made of a chiral metamaterial. The method of singular integral representation of a field is used to obtain a system of integral equations for the unknown distribution functions of the surface current densities of the array emitters. The results of calculating the current functions are given, as well as the dependence of isolation between the emitters on the chirality parameter.

New Type of Storage Resonator for an Electromagnetic Pulse Compressor

Wed, 04/01/2020 - 00:00

Abstract—The possibility of using a new type of storage resonator has been studied: an open resonator, the working oscillation of which is formed by counterpropagating surface waves of an open dielectric waveguide in an active electromagnetic pulse compressor. The simplest model of such a device is considered in detail; however, the results obtained during its rigorous electrodynamic analysis allow us to conclude that this device is promising for solving a number of urgent problems in the physics and technology of millimeter and submillimeter waves.

Heuristic Solution to the Diffraction Problem on a Superconducting Half-Plane

Wed, 04/01/2020 - 00:00

Abstract—The article presents a rigorous numerical solution, using the Wiener–Hopf method, to the problem of plane wave diffraction in a half-plane with generalized two-sided impedance boundary conditions describing various types of structures, including thin superconducting layers with a thickness comparable to the thickness of the skin layer. Expressions are obtained for the field scattered by the half-plane in the far field. For the rigorous solution, a heuristic formula is constructed that approximately describes the scattered field. It is shown that heuristic relations qualitatively and in many cases quantitatively correctly describe the scattering characteristics of the half-plane. A physical interpretation of the rigorous solution is proposed, based on the obtained heuristic relations.

Fast Acquisition Scheme of the Spread Spectrum Signals for Satellite Communications

Wed, 04/01/2020 - 00:00
Abstract

A four-channel parallel acquisition scheme combining partial matched filters and fast Fourier transforms (PMF-FFT) is proposed for the fast acquisition of the spread spectrum signals in satellite communication terminals installed into the offshore buoys with the high-dynamic movement, which is used tofinish data communication missions between the buoys and the satellite. Compared with traditional code phase FFT scheme, the new scheme reduces the maximum acquisition time to 26.5% and the maximum computation amount to 46.9%. It also improves about 4 times in the frequency resolution and 1.6 dB in the receiving sensitivity at the expense of computation complexity compared to PMF-FFT scheme. The parallel PMF-FFT scheme greatly reduces scallop loss, thus ensuring acquisition sensitivity. The parallel PMF-FFT scheme within the satellite communication terminal can ensure the fast and stable tracking of satellite signal by the violently moving antenna within 20 ms under level-4 sea state.

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