Том 62, № 10 (2017)

Processes accompanying the electrodynamic acceleration of a thin plate liner at a high accelerating current density are investigated. In addition to determining the electrical characteristics, shadow filming of the plate profile was carried out during the acceleration and the deformation of the profile in the region of fixed attachment to the current leads was monitored. A new experimentally reproducible effect in which the plate splits into three separate fragments, which is explained by nonuniform overheating by the current of the plate’s cross section and the electrodynamics of the process, was found. It was detected that, on the acceleration of copper liners, the current sheath is separated from the metal body of the liner and diverges in two directions. The nature of this phenomenon has not yet been determined.

It is revealed in the ray approximation that focusing of a converging spherical wave traveling through the boundary of a material medium can be retained if a lens-like pad is used on the medium boundary. Conditions imposed on the parameters of such a pad are presented. Dimensions of the volumetric spot in the region of the wave focusing point are estimated with consideration for the Fraunhofer diffraction at the edge of a round pad.

An iterative method for the amplitude–phase synthesis of antenna arrays based on control of the set of partial beams is proposed. In this method, two additional partial beams are added to the radiation pattern at each step. The shape of each beam is optimized with consideration for the difference between the synthesized and specified radiation patterns. Parameters specifying the shape of additional partial beams are chosen with the help of the genetic algorithm. The results of numerical studies allowing comparison of the proposed synthesis method to the least-squares method and the method based on control of the set of identical partial beams are presented.

The modulation functions (MFs) of generalized binary offset carrier (GBOC) signals of promising satellite radio-navigation systems, such as Galileo (European Union), global positioning system (GPS) (USA), and BeiDou/Compass (China), is estimated. Analytical expressions for the spectral density and energy spectrum of the single component of the GBOC-signal MF are obtained at different pulse multiplicity coefficients N_RSO of rectangular subcarrier oscillations and different duty cycles ρ. The spectra characterizing the important particular cases, namely, binary offset carrier and binary phase-shift keying signals are analyzed by means of the derived general formulas for GBOC signals. The Mathcad software package is used to construct graphs and discuss the properties of the energy spectra of single components entering into the GBOC-signal MF for the following types of modulation: GBOC(1, 1, ρ), GBOC(2, 2, ρ), and GBOC(10, 5, ρ).

There has been active research worldwide to develop the next generation, i.e., fifth generation, wireless network. Next generation mobile communication networks are broadening their spectrum to higher frequency bands (above 6 GHz) to support a high data rate up to multigigabits per second. This work examines how to substantially improve energy efficiency for next fifth generation mobile communication systems. It is depicted how by limited exchange of information between neighboring base stations it is possible to maintain quality of service, over a range of traffic loads, while enabling inactive base stations to sleep. Performance of distributed energy efficient topology management schemes are compared against the system without topology management. Performance evaluation is examined using both analytical and simulation based models. Extensive numerical results show that the schemes deliver a significant energy reduction in energy consumption in the mobile network systems.

Dynamic states and bifurcations in the phase-locked-loop (PLL) system with modified characteristic of phase discriminator and second-order low-pass filter in the control system are studied. The analysis is based on the dynamic model of a system with one and a half degrees of freedom in a cylindrical phase space. Complicated quasi-synchronous and asynchronous regimes are demonstrated for such a multistable system. The regimes are not possible for a conventional PLL system with sine-shaped characteristic of the discriminator.

The theory of acoustooptical (AO) interaction between light beams in the longitudinally inhomogeneous acoustic field is constructed with allowance for conditions typical of AO filtration. In the case of smooth acoustic inhomogeneities, analytical expressions for the spatially spectral characteristic relating the spatial spectra of incident and diffracted light beams are derived. The situation where a Gaussian light beam undergoes filtration in the acoustic field excited by a rectangular transducer is discussed in detail. The narrowband quasi-collinear AO filter based on a paratellurite crystal is simulated. It is demonstrated that the maximum diffraction efficiency and transmission-function shape distortion (with respect to the plane-wave model) of the given device depend to the greatest extent on the misalignment between the directions of the group velocities of interacting light beams.

It is shown that it is possible to use warm solenoids with copper winding screened with ferromagnetic shields in order to reduce the solenoid supply power by a factor of 1.8–2 while retaining the strength of the magnetic field in the working space for continuous gyrotrons operating in a frequency range of 24–30 GHz. The configuration of the shields as well as the shape and location of the correcting solenoids providing an extended (up to 10 wavelengths long) section of a uniform field in the region of the gyrotron cavity have been determined. It has been shown that introduction of an additional cathode coil into the magnetic system reduces the degree of nonadiabaticity of the magnetic field approximately by an order of magnitude and thereby makes it possible to use the magnetron injection gun for formation of a helical electron beam. Optimization of the configuration of the gun electrodes based on the trajectory analysis makes it possible to obtain an electron beam whose parameters are as good as parameters of the electron beams formed in classical adiabatic electron–optical systems of gyrotrons.

The resonance characteristics of dipole antennas based on armchair carbon nanotube are numerically investigated. The analysis takes into account the interaction of electrons with acoustic phonons which leads to the dependence of the electron relaxation time on the radius of the nanotube. The input impedance of the nanoantena as a function of the frequency of an incident electromagnetic field in the GHz range is obtained by the numerical solution of the Hallén’s integral equation. The dynamic quantum mechanical conductivity of armchair carbon nanotubes is used including the explicit dependence of the relaxation frequency on the radius. In this way, it is adequately described the resonant activity of the nanoantenna depending on the radius and length of the carbon nanotube. Current distributions are presented.

The possibility to use thin (1 mm or less) pseudocombline structures of λ/2 resonators made of sections of symmetric transmission strip lines from a dielectric material with ε_r = 2.2 as millimeter-wave bandpass filters is shown. It is established that the relative bandwidth of such filters can reach FBW = 0.1. Designs of stripline pseudocombline filters with alternating signs of the coupling coefficients, which are characterized by improved selectivity due to the attenuation poles located on both sides of the passband, are proposed; the filters contain stepped-impedance “half-wave” resonators with a new feature. The results of the computer simulation of the frequency characteristics of the filters in the frequency band of 31–122 GHz and the comparison of them with the characteristics of other filters are presented.