ENERGY CHARACTERISTICS OF A RECTANGULAR WAVEGUIDE
T-JUNCTION INTERACTING WITH A MULTIELEMENT VIBRATOR-SLOT COUPLING STRUCTURE
S. L. Berdnik,
V. A. Katrich, V. I. Kiyko, M. V. Nesterenko,
Yu. M. Penkin
The study of peculiarity of influence of the impedance
insertions on the electrodynamic characteristics of the rectangular
waveguide junctions, which are widely used in the
antenna-waveguide devices, is important for practical applications. A
mathe-matical model for E-plane T-junction of
rectangular waveguides with a three-element vibrator-slot coupling structure
was built using approximate analytical solutions of equations for induced
currents by a generalized method of electro-magneto-motive forces. The
distinctive feature of the model is the usage of variable surface impedance
along the monopole axes and constant impedance, distributed over the end wall
of the lateral semi-infinite waveguide. Multiparameter
energy characteristics of the junction in the single-mode waveguides are
presented including the case of meta-material coating the end wall of the
lateral waveguide. The possibility of efficient use of impedance coatings as
control element for power division between the output waveguide junction arms
is shown.
REFLECTION RESONANCES IN A RECTANGULAR WAVEGUIDE
SECTION WITH A PAIR OF ANTIPODAL RECTANGULAR POSTS
L. P. Mospan,
S. A. Prikolotin, А. А. Кirilenko
Intentional and controllable introduction of
attenuation poles into the frequency responses of frequency-selective devices
is in the great demand in the design of modern filters with complicated
performance. Successful implementation of such an approach is possible using
rectangular waveguide sections with metallic inserts. Here, the scattering
characteristics of such sections with a pair of antipodal rectangular posts as
waveguide units with rotational symmetry are studied. Comparative analysis with
the characteristics of a section with a pair of unidirectional posts is performed.
Spectral theory of open waveguide resonators is used in order to interpret the
resonant phenomena. Within the frames of spectral theory the reflection
resonances formed by such sections are the responses to the excitation of eigen
oscillations of complex frequencies. It is shown that the spectral theory
enables an order of magnitude more accurate (in comparison with the
conventional modal analysis) evaluation for basic parameters of the resonance
reflection, namely its frequency and the quality factor. The results obtained
make preliminary synthesis of frequency selective devices based on such
sections physically transparent and more accurate.
RADAR ELEVATION
ANGLES MEASUREMENTS OF LOW-ALTITUDE TARGETS OVER THE SEA BY ROOT-MUSIC METHOD UNDER INTERFERENCE FROM MULTIPATH AND THERMAL
NOISE ОF DIRECTION FINDER
Yu. A. Pedenko
The work is devoted to improvement of the accuracy of
radar measurements of elevation angles of low-altitude targets above sea level
when using the root-MUSIC, which is considered by experts as one of the
means to solve this problem. Unlike previous studies, which take into account
the multipath only, in this study the clutter is complicated by thermal noise
of radar. This allows to evaluate the capabilities of the method and provide
guidance on its application in the conditions close to reality. The study was
carried out by computer simulation. It covered various sea states at which the
conditions from specula to strong diffuse reflection were complied. In the
simulation a wide range of signal/noise ratio was used. The main focus was the
study of effects on measurement errors of a priori parameters of the method:
the signal subspace dimension and the order of autocorrelation matrix of
signals received by a multi-element antenna array. The recommendations of their
choice, allowing to minimize the errors of elevation measurement in different
conditions, have been developed. The results of the study extend the knowledge
of how to improve the methods for measuring the target elevation angle above
the sea.
RESEARCH ON THE UNDERLYING SURFACE BY RADIATION OF GLOBAL NAVIGATION SATELLITE SYSTEM
V. I. Lutsenko, D. O. Popov, I. V. Lutsenko
The investigation of the scattering signals features
on the land surface can be used to study the physics of scattering processes,
as well as for the establishment of multipath compensation methods for reducing
positioning errors in global navigation satellite systems. The possibility of
detecting the reflection areas on the underlying surface and estimating their
parameters by using radiation of global navigation satellite systems is shown.
The behavior of the signal levels for different satellites in urban areas is
analyzed. The influence of the reflection area’s characteristics on the
spectrum of the received radiations is considered; the method of determining
their location is proposed.
RADIANT SYSTEM BASED ON COLD PLASMA
V. V. Ovsyanikov
The actual problem of studying the basic properties and searching for methods
of improving the plasma radiator array, which is similar to the array of metal
or dielectric antennas, has been considered. This problem is not sufficiently
covered in the well-known publications, however, the great interest of
professionals to emitters based on cold plasma is due to the prospect of
creating effective multi-beam scanning selective plasma reconfigurable systems
or the plasma array of radiators (PAR). The article studies the main
electrodynamics parameters of PAR in the microwave range, characterizing it on
the one hand, as the load for the generator (receiver) of electromagnetic (EM)
signal. On the other hand, PAR is tested as transmitter of EM energy from the
point of view of its direction pattern (DP) and the main parameters of
radiation of PAR. When scanning DP beam, impedance distortion of PAR
transmitters and DP deformation are investigated. For comparison, similar
studies were carried out for the same design and configuration of the pattern
antenna (PA) of metal antennas. The studies have been carried out by PAR
modeling and their parameters calculations on computer in software environment
FEKO by integral equation method and method of moments for linear PAR from 4
emitters in the form of loop dielectric tubes filled with cold plasma under
reduced pressure. When studying the self and mutual impedances of the PAR and
metal PA in common mode for the distance between the transmitters 0.5λ0, where λ0 is the central wavelength
of the test range, it has been determined that electromagnetic interference
between antennas in PAR is less than in the metal antenna array, and when
reducing the distance between transmitters grating with 0.5λ0 – 0.25λ0 the relative change in
value of units of the input impedance of each radiator of PAR is twice less
than for a lattice of aluminum, which allows to bring together the radiator of
PAR without a substantial increase in interference between them. From
comparison of DP of radiant systems of PAR and aluminum arrays while scanning,
it is obvious that DP of PAR are less distorted than aluminum array. The
obtained results can be used for calculations and design of plasma array of
radiators.
PLASMA-BEAM SUPERHETERODYNE FREE ELECTRON LASER WITH H-UBITRON
PUMP WITH NON-AXIAL INJECTION OF ELECTRON BEAM
A. V. Lysenko, G. A. Oleksiienko
A cubic-nonlinear theory of a plasma-beam
superheterodyne free electron laser (PBSFEL) with H-ubitron pump and non-axial
injection of electron beam has been constructed. In the investigated system the
parametric resonance interaction between a space-charge wave and cyclotron wave
is realized. The signal wave saturation levels have been determined. It has
been found that the mode using a slow cyclotron wave has the highest saturation
level among all possible operation modes of the PBSFEL with H-ubitron
pump. The injection angle of the beam at which the electromagnetic signal gain
is maximal has been determined. It has been shown that PBSFELs using slow
cyclotron waves are able to create a powerful coherent electromagnetic
radiation in the millimeter wavelength range.
P. P. Maksymov
Construction of powerful sources of
electromagnetic oscillations of microwave range is an actual task for creating
modern semiconductor devices. In this paper the creation of powerful sources of
electromagnetic oscillations based on reverse-biased abrupt p–n-junctions
of avalanche-generator diodes (AGD) with external signal has been theoretically
grounded. Classification of modes of avalanche-generator diodes has been
carried out. The choice of oscillations generation mode is determined by the
parameters of AGD and input signal. It is shown that coherent, multifrequency
and broadband oscillations are generated in AGD. Power and spectral
descriptions of oscillations of AGD are presented. The research results are of
interest for the developers of powerful diode generators with the required
range, power and spectral characteristics.
THREE-CHANNEL PHASE METERS BASED ON THE AD8302
AND FIELD PROGRAMMABLE GATE ARRAYS FOR
HETERODYNE MILLIMETER WAVE INTERFEROMETER
A. V. Varavin, G. P. Ermak, A. S. Vasilev, A.
S. Fateev, N. Varavin, F. Zacek, J. Zajac
The paper presents the results of research
and development of two types of phase meters for heterodyne two-wave
“unambiguous” interferometer designed to measure the plasma density in tokamak COMPASS. The aim of this work is the creation of a phase meter capable of measuring fast
phase changes of each probing wave, and their phase difference. Plasma is
probed by two microwave signals with different wavelengths propagating along
identical paths to meet each other. Each analyzed signal acquires a certain phase
shift φ1 and φ2, and the “unambiguous” interferometer
determines the difference (φ1–φ2). The phase measurement is carried out by using
three-channel phase meters: a phase meter based on the pairs of the AD8302
and a phase meter based on field programmable gate arrays (FPGA). The
proposed circuit decisions and algorithms of signal processing allow to measure
phases in the range 0…360° in real time.
Z. А. Maizelis
For detecting and establishing the nature
of frequency noises in the oscillating system, it is very important to separate
different types of noises. For determination of characteristics of the
frequency noise it is necessary to study statistical properties not of actual
coordinate and its derivative, but of complex coordinate of oscillator. Its
moments do not depend on the amplitude noises that often can prevail in the
system. The growing interest in noises of frequency is related to the fact that
they determine the loss of coherence of vibrations in many systems, from the
devices based on Josephson contacts, to the nanomechanical resonators. The
knowledge of statistical characteristics of frequency noises inevitably present
in the devices of information read-out in quantum computers will allow correct
processing of the information in them. Here the influence of the telegraph
unbalanced noise of frequency on properties of electromechanical resonator is
studied. It is shown that the dependencies of the higher cumulants contain
features, which allow to separate the effects related to the presence of noise
of frequency. The results may be useful in the theory of nanomechanical
resonators, in processing the data, obtained in the radio-technical devices and
devices, based on Josephson contacts, in quantum computers, in the estimation
of precision of atomic clock.
RECONSTRUCTION OF IMAGES WITH LARGE NON-UNIFORM
INCREMENTS
S. I. Melnyk, S. S. Melnyk
In recent years, the range of tasks related
to the study of structures image elements of which are beyond the resolution of
matrix type sensors is becoming wider. Thus, the problem of their
reconstruction by applying algorithmic and information image processing
techniques is relevant. The problems emerging when observing objects whose
dimensions do not exceed several pixels of matrix of recorders have been
considered. It is shown that motion of the object relative to the matrix and
the use of multiple consecutive frames allow to improve the fidelity of shape
and true size of the object. This measurement information can be represented as
integrals along the trajectories on a three-dimensional lattice of space-time
pixels. The reconstruction of a heterogeneity function of pixels through the
use of the controlled motion of the test object and methods of computer
tomography. The possibility of determining the relative velocity of the object
in each of the frames using the blind method has been shown. The algorithm of
reconstructing images with large non-uniform increment during their arbitrary
and controlled relative motion has been elaborated.
V. P. Ruban
The estimation of synchronization
instability becomes actual in GPR due to the fact that this phenomenon affects
the accuracy of recording and reproducing the received signal forms and,
accordingly, the efficiency of use of digital signal processing algorithms. The
existing method for estimation of jitter of the GPR receiver using errors of
the converted signal amplitude is not universal and should be corrected for the
case of converter with incomplete charging of the storage capacitor. Simulation
of the stroboscopic conversion with instability of sampling interval for cases
of full charging (when the evaluation method gives correct results) and
incomplete charging of the storage capacitor has been done in this paper. The
relationship between the forms of probabilistic distribution of jitter and
errors of amplitude after stroboscopic conversion has been analyzed. The jitter
values originally specified in the simulation and the ones calculated
(reconstructed) by a known method also have been analyzed. According to the
simulation results, the limits of applicability of this method were determined.
It is shown that the direct application of the jitter evaluation method which
is right for the converter with a full charging gives incorrect estimates for
the one with incomplete charging of storage capacitor. Due to this, the signal
amplitude recovery procedure which allows obtaining a correct estimate of the
jitter of synchronization of GPR receivers operating in the mode of incomplete
charge storage capacitor has been suggested.