Volume 68, Nº 5 (2023)

A fast and rigorous method is developed for the electrodynamic analysis of an infinite cylindrical lens made of an artificial material, which is an array of hollow conducting cylinders of finite length and finite wall thickness, identically oriented along the lens axis. It is shown that the method makes it possible to calculate the characteristics of lenses consisting of multiple elements using a personal computer. The focusing properties of the lens are studied. The method is an alternative to and a technique to verify the approach based on the analysis of a lens made of a homogenized material with a refractive index of an infinite 3D photonic crystal.

A solution is obtained for the problem of synthesis of a metal–dielectric geodesic lens with central symmetry and, in the general case, inhomogeneous dielectric filling, which transforms the field of a point source into a given geometric optical field. By way of example using the obtained solution, the problems of synthesis of a geodesic lens antenna with layered and gradient dielectric filling are considered. In particular, solutions are obtained for lens antennas with in-phase output front and out-of-phase front that forms a tableshaped radiation pattern. The solutions are analyzed with the aid of numerical simulation using the finite element method.

An exact analytical formula is obtained that relates the experimental and theoretical parameters of the spectral line described by the Tsallis function, which includes the Gaussian, Lorentzian, line shapes intermediate between them, and super-Lorentzian as special cases. The procedure for the numerical calculation of the theoretical parameters of the line shape is studied by the example of electron spin resonance spectra. The effect of complicating experimental factors, including the noise and the analog signal digitization discreteness, on the accuracy of determining the theoretical Tsallian parameters is examined. It is shown that the proposed method for determining the theoretical parameters of the spectral line is not inferior in accuracy to the method for minimizing the root-mean-square error functional. It is predicted that the new approach can be used as an alternative to the available spectral line shape analysis techniques.

The technique for synthesis of analog devices with the use of elementary units of electronics, such as integrating, differentiating, adding (subtracting), multiplying (dividing), and multiplexing (demultiplexing) elements, is described. The proposed technique of synthesis is justified theoretically and the elementary units used are called the proposed element base of analog electronics. The description of the theory, as well as an example of developing a model of an analog low-pass filter with the use of the proposed technique, are
presented.

A numerical study of the delay in the excitation of oscillations of a magnetostrictive transducer in the frequency multiplication mode based on the model of coupled oscillators is presented. The non-stationary nature of the oscillations excited after the amplitude jump is revealed. The phenomenon is interpreted on the basis of the dynamic potential model. A numerical study of the development of oscillations in time has been carried out, and phase portraits of oscillations have been constructed. The fractal-like nature of nonstationary oscillations is established, which manifests itself in the preservation of the degree of their chaoticity with a change in the value of the calculation step in time.

A possibility of improving protective characteristics of transmission lines by cascading of multiconductor modal filters (MFs) with different geometric configurations is studied. Three-conductor MFs based on an asymmetric coaxial structure and a microstrip line and four variants of cascade structures consisting of two and three sections of such MFs are considered. Simulation of the time response to an ultrashort pulse  (USP) and parametric optimization are performed. Attenuation of USP by a factor of 27.4 is achieved.

Several methods to derive relationships between currents in the external circuit and variations in parameters of samples that induce such currents are considered. The relationships generalize the Shockley–Ramo theorem and may serve as a development of Kirchhoff laws for electrical circuits.

A relativistic magnetically isolated vircator with a magnetic mirror on a prelimit electron beam is proposed. Its computer simulation has been carried out. The phase dynamics of an electron beam in a vircator has been studied. It is shown that a number of virtual cathodes appear in the beam after the beam is reflected from the magnetic mirror. The output microwave characteristics are calculated: the average power and the spectral composition of generation, containing a set of narrow spectral lines and their harmonics. The effect of the mirror ratio on the average output power and on the frequencies of the spectral lines is studied. It is found that the power increases with the growth of the mirror ratio. The frequencies of some spectral lines increase with the mirror ratio, while the frequencies of other lines do not depend on this ratio.

Changes in the morphology and structure of the GaAs surface during the deposition of an Au film by thermal evaporation in vacuum have been studied. It has been found that the deposition of an Au film with the participation of a flow of particles and light from a heated evaporator causes the appearance of photoeffects in the near-surface GaAs layers, including light diffraction on surface acoustic waves, the growth of whiskers, and electron emission, which leads to the formation of microcracks on the GaAs surface and the growth of GaAs crystallites. It is shown that the structure and composition of the film boundaries of Au and GaAs surfaces depend on the electron concentration in gallium arsenide, which ultimately determines the properties of the electrophysical parameters of the Au–GaAs contacts.

In the second approximation in coordinate system x^i , i = 1, 2, 3 connected with current tubes x^2=const , the equations of axisymmetric and plane-symmetrical electrostatic flows are formulated in three versions of the geometrized theory: in l-representation, longitudinal coordinate x^1 is not related to the physical parameters of the beam, phi- and W-representations, when as x^1 the potential of the electrostatic field is used,  x^1=phi, or the potential of generalized momentum x^1=W.