Described trends in the application of two-dimensional-periodic absorbing structures in optical and THz range. The results of calculation of the scatter and reflection of multilayer structures. Designed optimal parameters of the structures to monitor the greatest effect absorption.
Keywords: resonant absorption, plasmons, reflection coefficient, diffraction gratings, periodic structures
Diffraction characteristics of the gratings are calculated by two methods - method of approximate boundary conditions and a strict method based on the numerical and analytical solution of the two-dimensional integro-differential equation. Results of the graphene diffraction gratings calculations are presented.
Keywords: graphene, graphene gratings, volume integral equations, plasmons, coefficient of reflection
The paper is devoted by studying of the correctness of the antenna pattern adaptive control problem in a randomly inhomogeneous medium. We use spectral methods for the solving the Helmholtz equation with variable parameters in the frozen medium approximation. We have proved the correctness of the problem of a given antenna pattern forming in a randomly inhomogeneous medium for the measured distribution of the complex wave amplitude in the plane of receivers in the first time. The possibility of using an antenna with a synthesized aperture for adaptive correction of the antenna pattern for maximization of communication channel capacity is substantiated. We use the refractive index model as the sum of the deterministic and random components in numerical modeling. The sampling intervals were chosen in accordance with the sampling theorem. The analytic expressions with given parameters were used as a model of the law of the antenna array operation. The results of numerical simulation confirmed that, in the first approximation, the problem of the antenna pattern controlling of a transmitter with a synthesized aperture based on the distribution of the complex wave amplitude measured in the plane of receivers is correct. It allows to create a system of adaptive antenna pattern correction for maximization of communication channel capacity.
Keywords: communication channel, directional pattern, complex amplitude, synthesized aperture, angular spectrum method, adaptive control
The paper discusses the matters of required gain approximation in the frequency range of operation using the Chebyshev criterion and Remez exchange algorithm. The equiripple problems have been solved, which yields polynomials in the form of the fourth order multipliers that approximate the different gains with different frequency ratios. The obtained polynomials make it possible to implement bandpass amplifiers with the required selectivity and gain. The dependencies of figures of merit (for dynamic and frequency ranges, frequency response stability) on the relationship of transfer function sensitivity to element parameters deviations have been analyzed. The criterion of optimality for bandpass amplifiers circuits in the form of the product of gain by transfer function sensitivity to active element parameters deviations has been defined. A circuit design for the fourth order bandpass amplifiers employing a single active element has been suggested. Design ratios for elements’ parameters that provide the minimum value of the optimality criterion over the frequency range of operation have been calculated. Comparison of the suggested and known fourth order function implementation has been made. It has been proved that the figures of merit of selective amplifiers constructed according to the suggested circuit design can be significantly improved.
Keywords: approximation, frequency response, selective amplifier, active two-port network, integrated amplifier, sensitivity characteristics, dynamic range, intermediate frequency amplifier, a noise level, a function of sensitivity
This article examines the processes occurring in the input circuits of a universal AC control system. The calculated ratio of the power flow control algorithms between networks, provided consumption given the current nature of any nature in the generation of power. The dependences of the calculated ratios.
Keywords: a universal system of alternating current control; power flow control; vector diagram; Power network voltage inverter, active rectifier, capacitive drive.