Transmission of vortex electrons through a solenoid

We argue that it is generally nonstationary Laguerre-Gaussian states (NSLG) rather than the Landau ones that appropriately describe electrons with orbital angular momentum both in their dynamics at a hard-edge boundary between a solenoid and vacuum and inside the magnetic field. It is shown that the r.m.s. radius of the NSLG state oscillates in time and its period-averaged value can significantly exceed the r.m.s. radius of the Landau state, even far from the boundary. We propose to study the unconventional features of quantum dynamics inside a solenoid in several experimental scenarios with vortex electrons described by the NSLG states. Relevance for processes in scanning and transmission electron microscopes, as well as for particle accelerators with relativistic beams is emphasized.Comment: 6 pages, 2 figure

MODEL OF EVALUATING THE LEVEL OF PARASITIC PHASE FLUCTUATIONS IN THE OUTPUT SIGNAL OF THE FREQUENCIES SYNTHESIZER

The article describes the actual problem of calculating the level of parasitic fluctuations of the phase of the output signal of the frequency synthesizer of indirect synthesis based on phase-locked loop. The basis for constructing a polynomial model is the model of output noise distribution based on the Leeson generator principle. The described principles of operation of frequency synthesizers with a divider with a fractionally variable division factor allow us to understand the nature of the appearance of the so-called shot noise. The analysis of the characteristics of all the elements included in the frequency synthesizers makes it possible to ensure that the noise components of each individual unit can be represented as a polynomial. The possibility of using the developed polynomial model for estimating the noise level in frequency synthesizers at the stage of selecting the structure of the proposed implementation structure is proposed. As a demonstration of the adequacy of theoretical calculations, the results of phase noise simulation by the polynomial method for all circuit components are presented, as well as a comparison of the results obtained with the simulation of a similar frequency synthesizer in the «ADIsimPLL» simulation package from Analog Devices. Such a simulation allows not only to obtain the level of side components in the spectrum of the output signal, but also to estimate the degree of influence of each specific element of the circuit

Method of determining the coordinates of the radio signal source in satellite communication systems

Telecommunications have penetrated deeply into all spheres of human activity. Due to the use of digital technologies, it has become possible to transmit and receive information of various kinds in one stream (not separately). Three geostationary satellites are sufficient to provide data transmission from anywhere in the world to another point using artificial Earth satellites. Data transmission systems using the satellite should contain at least two Earth Stations and a repeater of the communication satellite. There are no means of combating any types of artificial interference in the Earth Stations equipment. The jammer, an illegitimate user, can emit a signal from any point in space within a telecommunications satellite system. The paper provides an analysis of existing methods for determining the coordinates of a radio signal source, describes a method for determining the coordinates of an radio signal source (illegitimate user) in satellite telecommunications systems using a geostationary spacecraft. The development was based on a three-position virtual antenna array, the positions of which determined the base of an irregular tetrahedron, and the radio signal source itself was its vertex. In the course of the solution, canonical equations of straight lines in space were compiled, at the intersection point of which the source of the radio signal is located. The coordinates of the radio signal source were the roots of the system, when finding the unit vectors lying on these lines

Determination of the range of the spacecraft

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.As a result of the gravitational attraction of the Sun/Moon/Earth, the pressure of solar radiation and other factors, the spacecraft located in the geostationary orbit deviates from the real orbit. The position of the spacecraft is regulated by a short pulse switching by correcting engines. This requires highly accurate measurement of the range to a spacecraft located in a geostationary orbit. The article describes a method for measuring the range not only by rangefinder, but also by command signals of the tracking, telemetry and command subsystem of a spacecraft, which allows for continuous measurement. Due to the fact that the reserves for improving the accuracy of measuring the range of a spacecraft, with known limitations as part of a single ground station, are almost exhausted, one of the perspective ways to solve this problem has been proposed. It consists of using several satellite earth stations, which are stationary located at various known locations on the Earth's surface and which receive any signal transmitted by a spacecraft located in a geostationary orbit. This method eliminates the using of special ranging signals and antennas of large diameter. For highprecision range measurement, synchronization of generators of a satellite earth stations by time signals transmitted by GLONASS or GPS navigation satellites is required. In addition, the using of various types of signals for determining the range, when measuring the delay time or phase difference, is considered. Relevant conclusions are made

Trends in dynamics of forest upper boundary in high mountains of northern Baikal area

Studies of spatial-temporal variability of the upper boundary of the forest on the north-western coast of Lake Baikal (Baikal and Upper Angara Ridges) are performed on the base of the analysis of forests renewal processes and of the dynamics of larch radial increment in the ecotone of the forest upper boundary and out of it. The presence of a large amount of well-developed uplands and circuses with considerable heights drops in the structure of mountain system favours formation of interrupted boundary between forest and subgoltsy belt. The timber stand of the upper forest boundary in the studied area is represented by Daurian larch. Three tree-ring chronologies of larch are obtained. The longest chronology is obtained for mountain taiga belt of Baikal Ridge and is as long as 460 years. Since 1980ies, a sustainable trend of increase of radial trees growth is observed. It is observed the most distinctly in trees of the upper forest boundary on the Baikal Ridge. There is advancing of trees species into subgoltsy belt and into mountain tundra, which depends, respectively, on slopes heights, exposition and tilting, on sites of growth of concrete cenoses. Modern peculiarity of the vegetation of the studied area is presence of abundant viable larch undergrowth (from 2–3 to 25 y.o.) and fir in the ecotone of upper forest boundary and in subgoltsy belt, as well as appearing of single specimens of spruce. Main undergrowth mass (2/3) is presented by trees aged in average 15–25 y.o., i.e., they appeared in late 1980ies. Due to increase of snow cover thickness in winter, the trees young growth obtained great protection from freezing resulting in the increase of ability of young growth to live up to elder age