L.P. Mospan, S.L. Senkevich, and V.I. Tkachenko
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Waveguide Filters Based on Capacitive Irises with Additional Attenuation Poles
The new design of directly-coupled band-pass filters insuring inclusion of additional stopband poles is offered. The stopband poles are inserted by means of cutting additional slots in capacitive irises of the filter. The slots are parallel to broad walls of a waveguide. Such method of inclusion of additional poles does not result in increasing dimensions of the filter. Modification of the filter irises results in insignificant change of their K-inverters. They are easily trimed to the desired value. The dimensions of the additional slots determine position and quality factor of the additional stopband poles. They can be situated both in a parasitic transmission band and in a transition region of the fundamental band. The numerical examples for band-pass filters in WR 90 waveguides are given. They show increasing the frequency selectivity and stopband extension. It is reached without a loss increase in the filter transmission band. An example of synthesis of a low-pass filter with a low loss level in a transmission band is also presented.
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V.I. Lutsenko
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Application of the Angular-Noise Criterion to Improve Small-Size Above-Water Target Detection Efficiency
Statistical characteristics are investigated of fluctuations of angles of arrival of signals scattering by small-size above-water objects, sea surface and precipitation. Algorithms of detection of objects using information on angle of arrival of received signal are proposed, and their efficiency is investigated. Possibility in principle is shown to use the features of angular noise of objects and passive disturbances created by reflections from sea and precipitation for improving of efficiency of detection of above-water objects.
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V.M. Fityo, Ya.V. Bobytskiy, and H.P. Laba
National University "Lvivska Politekhnika"
12, Stepan Bandera St., 79013 Lviv, Ukraine
Band Structure Analysis of 1D and 2D Photonic Crystals by Coupled Wave Method
The electromagnetic field of wave that propagates in the crystal is decomposed into plane waves in the classic method of computation of photonic crystal band structure. The problem of finding of the allowed frequencies for a wave vector in the first Brillouin zone is reduced to finding of eigenvalues and eigenvectors of the corresponding dimensional representation matrix, which provides for the required precision for finding of the allowed frequencies. Due to slow convergence of decomposition into plane waves it is necessary to solve the matrix equation of large dimension that requires considerable time of calculation. The suggested method of determination of the allowed frequencies is based on the coupled wave method (CWM) at the corresponding setting of periodic boundary conditions. This method is especially simple for 1 D photonic crystals and it consists in finding the solution to the eigenvalue problem of ÒÕ = pX
type and the check-up whether the absolute value of eigenvalue p is equal to one. The dimensional representation of quadratic matrix T is 2x2.
The eigenvalue problem of this type appears as a result of the application of the so-called T-algorithm, which is stable for 1D photonic crystal.
The solution leads to the eigenvalue problem of ÒÕ = p RX type and the check-up whether the absolute value of eigenvalue p is one at given
frequency v and component kx of wave vector for 2D photonic crystals, too. The eigenvalue problem of type of ÒÕ = p RX arises due to the application
of stable numerical S-algorithm. Dimensional representation of matrices T and R is 2Nx2N, where N is a number of the coupled waves.
Frequency will be allowed, if the absolute value of eigenvalue is one. The dimensional representation 2Nx2N of the matrix equation in the suggested method
is equivalent to the dimension N2xN2 of the classic method from the point of view of calculation accuracy. Stable S-algorithm of calculation is developed.
The calculations of band structure of 1D and 2D photonic crystal of the simplest form are performed. The dependencies of calculation accuracy upon the number of the coupled waves (N varies from 1 to 29) are obtained.
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N.N. Beletskii and S.A. Borysenko
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Spin-Filtering Electron Currents
in Semimagnetic Semiconductor Nanostructures
Spin-filtering electron currents have been studied in the nanostructures based on ZnMnSe-semimagnetic semiconductors. It is shown that the thicknesses of nanostructure layers and the Mn-concentrations in the layers can be chosen in such a way that the spin polarization of the electron current can reach very large values in relatively low external constant magnetic fields. It has been found that the degree and sign of the spin polarization of the electron current can be changed with the help of the bias voltage applied to the semimagnetic nanostructure. It has been determined that the sign reversal of the spin polarization of the electron current is concerned with the resonance tunneling of spin-up electrons through the double-barrier energy potential formed in the nanostructure at the expense of choosing the composition of semimagnetic layers.
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Yu.I. Malyshenko, V.L. Kostina, and A.N. Royenko
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Frequency and Temperature Dependencies of Water Complex Permittivity over Microwave and Terahertz Ranges
A predictive model for calculating the frequency and temperature dependencies of complex permittivity (CP) of water over a wide frequency range (f=0.03-3THz (Ë=10.0-0.1mm)) is proposed. This model takes account of the Debay-polarization-to-resonance mechanism smooth transition and ensure that the experimental data are in good agreement with the predicted ones to an error of no more than 5%
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G.P. Yermak, A.V. Varavin, and V.P. Kochergin
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Solid-State Transceiver System for Vector Mesurements in Two-Millimeter Wave Band
The results of development and investigation of the 2 mm-wave solid-state transmitting-receiving system for millimeter-wave band vector network analyzer are presented. The system is based on two electrically controlled 2-mm band sources on the basis of active high-order IMPATT diode multiplying sources. The sources are synchronized with the help of the phase locking system, in so doing one of them is acting as the transmitter and the other one functions as the local oscillator for the receiver part. The amplitude and phase characteristics of the system are investigated and spectra of signals from the sources at synchronous mode of their operation are measured.
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