Journal of Communications Technology and Electronics

The applicability of the method for solving the problem of diffraction by resistive gratings, based on solving the problem of exciting the Floquet channel by current elements to the calculation of structures with planar ideal gratings, is shown. A quasi-static approximation formula is obtained for the effective dielectric constant of a flat single-layer grating based on perfectly conducting squares. Comparative calculations of the reflection coefficient by diffraction and quasi-static methods for single-layer and two-layer gratings with dielectric layers are carried out.

The problem of excitation of a cylindrical microstrip structure by a plane wave is considered. The structure is a printed element on a circular dielectric substrate containing a coaxial metal cylinder. In the scattering regime, the structure under study adequately simulates a cylindrical microstrip antenna operating at resonance frequencies. The printed element is equivalent to the radiator of this antenna. The problem is solved in the spectral domain with the use of the method of moments and piecewise-specified basis functions. The effect of the radiator’s shape on the radar cross section of the structure is investigated. It is shown that a change in the radiator’s topology substantially affects the formation of new oscillation modes whose resonance frequencies noticeably shift to the lower frequency region from their positions in the case of a radiator having a rectangular cylindrical shape.

Two-dimensional problem of diffraction of a plane electromagnetic TM wave by a cylindrical golden 2D nanostructure is considered. The contour of the cross-section of this structure is a star-shaped curve. The spectra of the scattering cross section and scattering pattern are calculated using a rigorous numerical method in the light wavelength range 400 nm < λ < 900 nm. The influence of the medium loss and geometric dimensions of the structure on the scattering cross section and scattering pattern is investigated. It is shown that it is typical for this structure to have one resonance of the scattering cross section and several resonances in the scattering spectrum in the region of values $$kD < 1$$ (where $$k = {{2\pi } \mathord{\left/ {\vphantom {{2\pi } \lambda }} \right. \kern-0em} \lambda }$$ , $$D$$ is the maximal dimension of the structure, and $$\lambda $$ is the wavelength). It is also shown that, because of the real gold loss, it is impossible to observe multipole resonances of the scattering cross section. The effect of the degeneracy of plasmons and the near field of the structure is discovered. The influence of the geometric dimensions of the structure on the scattering cross section and absorption spectrum is demonstrated.

It has been proved that electromagnetic coupling coefficients K of resonators in stripline filters with homogeneous dielectric depend only on geometric parameters of the filter designs and are independent of relative permittivity εr (if the dielectric is two-layer, coefficients K depend only on geometric parameters of the filter designs and ratio εr2/εr1). It has been shown that the revealed earlier influence of permittivity εr and the operating frequency on K is only a consequence of the influence of the length of stripline resonators on K: the lesser is the length, the larger is coefficient K. It has been found that these propositions enable consideration of frequency characteristics of the same design of the bandpass filter in different frequency bands by changing εr and performing slight changes in outermost resonators. The results of computer simulation of the transfer of frequency characteristics of a stripline bandpass filter from 3 GHz to 6 and 12 GHz with retaining the fractional bandwidth and selectivity are presented.

In this paper, we study the properties of X-ray diffraction reflection spectra of multilayer periodic AlGaAs/GaAs heterostructures depending on the thickness and composition of the layer material and number of periods. The number and intensity of additional diffraction maxima on the rocking curves are shown to increase with an increase in the layer thickness and number of periods. The layer composition does not affect the number of maxima but changes their angular position and the full width at half maximum. Numerical calculations were compared with experimental spectra measured for a heterostructure grown by molecular beam epitaxy and consisting of 50 periods in which the AlxGa1–xAs barrier had a composition of x ≈ 26.7% and a thickness of d ≈ 51.6 nm while the GaAs quantum well had a thickness of d ≈ 4.6 nm. The calculated parameters are found to be in good agreement with the technological data and the results of transmission electron microscope measurements.

It is demonstrated that, when the function describing the impedance distribution on a plane belongs to a certain class, a wave normally incident on the plane is diffusively scattered and absorbed rather than reflected. When the contour of a finite plane segment satisfies a certain condition, a wave is not reflected by this segment. Such plane figures can provide for antiradar protection. In particular, they can be made from a lossless material.

Multiple-input multiple-output systems are communication systems employing multiple transmitting and receiving antennas. In the present study, a new generalized concatenated signal-code construction is proposed. Its inner codes are embedded Golden codes, and its outer codes are products of Reed-Solomon codes. New algorithms for decoding inner codes, outer codes, and the generalized signal-code construction itself are proposed. The decoder for space-time Golden codes makes it possible to obtain a measure of reliability for certain symbols without an increase in the number of arithmetic operations. The decoder for outer product codes removes the “floor” on the error-probability curve. In addition, the lower bounds of decoding-error probability for the product-code iterative decoders have been obtained. The error-correcting capacity of the new decoder for the generalized concatenated construction is higher than that of the currently known decoders. A computer simulation has shown the efficiency of the proposed construction and decoding algorithms.