Volume 61, Nº 9 (2016)
- Ano: 2016
- Artigos: 12
- URL: https://journals.rcsi.science/1064-2269/issue/view/12332
On the 60th Anniversary of the Journal of Communications Technology and Electronics
Integral equation method in problems of electromagnetic-wave reflection from inhomogeneous interfaces between media
Resumo
Problems on reflection of a plane electromagnetic wave from various irregular interfaces between media are studied by the integral equation method in the cases of two- and three-dimensional incident electromagnetic field. The reflecting surfaces are meant as periodic transparent interfaces between two media and plane boundaries with locally inhomogeneous and transparent sections. The boundary value problems for the system of Maxwell’s equations in an infinite domain with an irregular boundary are reduced to Fredholm or singular integral equations, depending on the problem considered. Numerical algorithms for solving such integral equations are developed. Results of calculation of currents induced on inhomogeneities and characteristics of the electric field in the far zone are presented.Problems on reflection of a plane electromagnetic wave from various irregular interfaces between media are studied by the integral equation method in the cases of two- and three-dimensional incident electromagnetic field. The reflecting surfaces are meant as periodic transparent interfaces between two media and plane boundaries with locally inhomogeneous and transparent sections. The boundary value problems for the system of Maxwell’s equations in an infinite domain with an irregular boundary are reduced to Fredholm or singular integral equations, depending on the problem considered. Numerical algorithms for solving such integral equations are developed. Results of calculation of currents induced on inhomogeneities and characteristics of the electric field in the far zone are presented.
Frequency tuning of the spin-injection radiation in the magnetic contact junction
Resumo
The frequency tuning of the terahertz radiation of spin-injection oscillator based on magnetic contact junction that is formed by contacting ferromagnetic metal layers with different magnetizations is analyzed. Under the current-induced spin injection from one magnetic layer (injector) to another (working) layer, the interval of radiation frequencies is determined by the current density in the magnetic contact, the mismatch angle of the magnetizations of injector and working layer, and the equilibrium spin polarization. The wide-range tuning of terahertz frequencies of the spin-injection radiation can be implemented using variations in the above parameters.
Electrodynamics and Wave Propagation
Tapers in waveguides with sharp edges
Resumo
The cross-section method is extended to the case of waveguides containing sharp metal edges. Such structures comprise strip lines, microstrip lines, and slot transmission lines. Relationships for eigenmode coupling coefficients in a section with parameters varying in the longitudinal direction are derived by passing to the limit: from a waveguide with smooth contour of the cross section to a waveguide with sharp edges. These relationships are applied to a single-mode strip line with conductor having variable width. It is shown that the obtained results agree with the results of the theory of microwave transmission lines.
Investigation of a frequency-selective surface based on a planar mushroom-shaped metamaterial with an electronically tunable stopband
Resumo
A design of a band-stop frequency-selective surface based on a planar mushroom-shaped metamaterial with an electronically tunable stopband has been proposed and investigated. The results of numerical simulation and experimental measurements of the parameters of a finite section of the metamaterial with mounted varicaps are presented. These results illustrate the shift of the structure stopband occurring simultaneously with a change in the capacitance of the lumped elements. Frequency dependences of the inherent dielectric parameters have been obtained. They indicate the presence of negative values of the effective permittivity and effective permeability of the proposed structure and the presence of the surface impedance that significantly exceeds the free-space characteristic impedance and is frequency-tunable.
Statistical Radiophysics
Localization of invariant compacts of a phase-lock system
Resumo
The localization method, which makes it possible to find regions in the phase space that contain all attractors of the system is used to analyze a phase system. Systems of inequalities describing such sets have been obtained. Phase-lock systems of the fourth and third order, which allow existence of chaotic attractors of various types, have been investigated.
Theory and Methods of Signal Processing
Estimation of the number of orthogonal signals with unknown parameters
Resumo
Algorithms for estimation of the number of signals with unknown amplitudes and several non-energy parameters are synthesized on the basis of the modified maximum likelihood method. Asymptotic values of the probabilities of the error in estimation of the signal number are determined. The effect of a reduced volume of the a priori domain of possible values and the dimensionality of the vector of unknown non-energy parameters on the quality of operation of the algorithms for estimation of the number of signals is investigated.
Microwave Electronics
Numerical investigation of the electrodynamic properties of a K-band multibeam monotron with a three-gap cavity
Resumo
The results of 3D numerical modeling of a low-voltage compact K-band multibeam generator of monotron type with two different modes of electron beam bunching (bunching only in the first gap or successive bunching in the first and the second gaps) are presented. These results demonstrate that it is possible to achieve a microwave radiation power exceeding 1 kW at a frequency of 18.21 GHz with an accelerating voltage of 2.45 kV and an overall efficiency of approximately 44%.
A 240–380 GHz orotron with a double-row periodic structure and multifocal focusing spherocylindrical mirrors
Resumo
The potentialilty of increasing the generation power of a 240–380 GHz orotron with a double-row periodic structure and multifocal focusing spherocylindrical mirrors of the open cavity (OC) in the range of 290–350 GHz is studied experimentally. This range is of interest due to the fact that it contains two atmospheric transparency windows at frequencies of 306 (λ = 0.98 mm) and 341 GHz (λ = 0.88 mm).
Electron and Ion Emission
Improvement in the properties of glassy-carbon field-emission cells in forming spikes with a high aspect ratio via laser milling
Resumo
Various opportunities to improve the quality with which an electron flow is formed by cathode arrays comprising multilayer planar structures with the vertical arrangement of autoemitters are investigated with the help of numerical simulation. It is demonstrated that field-emission cells with glassy carbon emitters shaped as smooth needles with aspect ratios of several hundreds and cathode arrays on their basis can be obtained using the efficient technology of microsized milling by laser radiation with nanosecond pulses. Field-emission cells with a vertically oriented ring blade-shaped emitter and emitters created by single spikes located on a circumference are comparatively analyzed.
Physical Processes in Electron Devices
Noise characteristics of autodynes with frequency stabilization by means of an external high-Q cavity
Resumo
The expressions describing the autodyne (AD) response are obtained with allowance for the internal noise of a frequency-stabilized microwave oscillator subjected to the action of its self-radiation reflected from an object. The results of analyzing the AD and noise characteristics of the stabilized oscillator built around the band-reflecting filter with resistive coupling are presented. The conditions leading to the appearance of the periodic non-stationarity of noise characteristics are established. It is demonstrated that frequency stabilization is ensured by a gain in dynamic range. The experimental data on unstabilized and stabilized hybrid-integral AD oscillators based on the two-mesa Gunn diode of 8-mm range are presented.
Novel Radio Systems and Elements
Tunnel superconducting junctions for a cryogenic multiplexing system
Resumo
the possibility of using superconductor–insulator–superconductor (SIS) tunnel junctions in a cryogenic multiplexing system for setting an ac current through arrays of transition edge sensors and reading out the received signal, as well as for setting a dc current through arrays of superconducting quantum interferometers is studied. Operation of the SIS frequency converter at relatively low (below 10 GHz) working frequencies is experimentally investigated. Different operation regimes are implemented; the conversion loss in the quasiparticle mode is found to be 8 dB and the output saturation power is–58 dBm. The possibility of up-conversion of several input signal frequencies simultaneously is demonstrated. It is shown that the SIS junction can be used as a current source controlled by an external RF signal.