Begell House Inc.
Radio Physics and Radio Astronomy
RPRA
2152-274X
3
2
2012
USING PHASE DYNAMIC CROSS-SPECTRA FOR WIDEBAND RADIO ASTRONOMY OBSERVATIONS: EXPERIENCE FROM THE UTR-2 RADIO TELESCOPE
89-102
10.1615/RadioPhysicsRadioAstronomy.v3.i2.10
V. L.
Koliadin
Institute of Radio Astronomy, National Academy of Sciences of Ukraine, 4, Chervonopraporna St., Kharkiv, 61002, Ukraine
radio astronomy
radio telescopes
phase spectrum
dynamic spectrum
signal processing
radio interferometry
Dynamic spectra are widely used in radio astronomy for processing observation data to characterize time-frequency distribution of the received emission total power. The paper presents a data processing technique which extends capabilities of such a time-frequency analysis through involving information on the phase difference between signals from sub-antennas composed of elements of the radio telescope antenna system. Dynamic phase spectra, which represent time-frequency dependences of the cross-spectrum phase for two signals, are formed by means of interferometric processing algorithms to be then used jointly with the conventional dynamic power spectra. The technique has been implemented at the UTR-2 radio telescope and used for several years for visual detection of the sought radio emission, recognition of false signals received by the antenna side lobes, and for discrimination of radio bursts observed within the main beam. The use of two pairs of antennas with noncollinear baselines makes it possible to determine the emission direction of arrival for each point on the time-frequency plane. The efficiency of the technique as applied to different types of radio emission are illustrated by examples of processing observational data for the Sun, Saturn and flare stars.
A THEORY OF RADIATION BY A RELATIVISTIC CHARGED PARTICLE MOVING THROUGH A CURVED MAGNETIC FIELD: THE UNDULATOR-CURVATURE MECHANISM
103-112
10.1615/RadioPhysicsRadioAstronomy.v3.i2.20
Ya. M.
Sobolev
Institute of Radio Astronomy, National Academy of Sciences of Ukraine, 4, Chervonopraporna St., Kharkiv, 61002, Ukraine
curvature radiation mechanism
synchro-curvature radiation
undulator radiation
pulsar
The angular and frequency spectra are derived for the radiation from an ultra-relativistic charged particle moving along a curved helical path. Contributions to the radiation intensity are due to the curvature radiation and undulator radiation mechanisms, associated with many revolutions of the particle about its drift path. The curvature radiation is plane polarized, while the undulator radiation is characterized by a circular polarization. The impact of the magnetic field-line curvature upon polarization of the undulator radiation is analyzed. A hypothesis has been put forward on the feasibility of the undulator radiation mechanism in pulsar magnetospheres.
INVESTIGATION OF LARGE-SCALE STRUCTURE OF SOLAR WIND AT SPATIALLY SEPARATED RADIOTELESCOPES
113-122
10.1615/RadioPhysicsRadioAstronomy.v3.i2.30
M. R.
Olyak
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
interplanetary medium
scintillation spectrum
scintillation cross-spectrum
spectrum of interferometer response power fluctuations
Expressions for the second and fourth field moments which account for the solar wind flow structure are obtained with the Feynman path-integrals method. The expressions for scintillations of power spectra for the radiation received by a single antenna and by two spatially separated antennas are obtained and analyzed. For different solar wind models it was shown that the method of the dispersion analysis of phase speed, along with the scintillation method, allows to most fully investigate the solar wind flow structure at distances from the Sun exceeding 1 AU. This method enables to define not only the presence of solar wind flows of various speeds but also their extent and parameters.
PARAMETER DETERMINATION OF KILOPARSEC JETS AT LARGE REDSHIFTS BY THEIR RADIO AND X-RAY EMISSION
123-130
10.1615/RadioPhysicsRadioAstronomy.v3.i2.40
M. S.
Butuzova
Institute of Radio Astronomy, National Academy of Sciences of Ukraine, 4, Chervonopraporna St., Kharkiv, 61002, Ukraine
kiloparsec jet
radio and X-ray emission
jet to line of sight angle
inverse Compton scattering
quasar 1745+624
quasar PKS 1127-14
The 1745+624 and PKS 1127−14 quasar jets are considered. The X-ray emission of the near-central source knots is produced by the inverse Compton scattering of quasar radiation, while the inverse Compton scattering on the cosmic microwave background occurs at distant knots. The competition of these mechanisms has allowed to estimate the angles between the jets and the line of sight. The ratio of X-ray to radio flux densities of distant knots is shown to conform to the theoretical dependence on the redshift.
SCINTILLATIONS OF RADIO SOURCE 4C21.53 AT DECAMETER WAVELENGTHS AND ELONGATIONS 43°−138°
131-138
10.1615/RadioPhysicsRadioAstronomy.v3.i2.50
Nikolai Nikolaevich
Kalinichenko
Institute of Radio Astronomy, National Academy Sciences of Ukraine
interplanetary scintillations
decameter wavelengths
digital spectrum analyzer
The statistical quantities of interplanetary scintillations at decameter wavelengths (scintillation index, power spectrum, cross-correlation function, probability density function) for the strong and weak scattering cases are estimated by analyzing the observations of 4C21.53 radio source scintillations. The obtained results can be used to test the models applied for analyzing interplanetary scintillations data at decameter wavelengths. The high efficiency of the DSP-z wide-band digital spectrum analyzer for interplanetary scintillations observations at decameter wavelengths is shown.
COMPARATIVE ANALYSIS OF IONOSPHERIC EFFECTS AS OBSERVED DURING "PROTON" ROCKET FLIGHTS UNDER DIFFERENT SPACE WEATHER CONDITIONS
139-148
10.1615/RadioPhysicsRadioAstronomy.v3.i2.60
L. F.
Chernogor
V. Karazin National University of Kharkov, 4, Svoboda Sq., Kharkov, 61077; A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine, 12, Academician Proskura St., Kharkov 61085, Ukraine
T. G.
Zhivolup
Institute of the Ionosphere, National Academy of Sciences and Ministry of Education, Science, Youth, and Sports of Ukraine, 16, Chervonopraporna St., Kharkiv, 61002, Ukraine
ionospheric disturbances
rocket launches
magnetic storm
magnetohydrodynamic waves
internal gravity waves
Observational results are presented concerning perturbations in the ionosphere associated with the launches and flights of the "Proton" rocket on March 29, 2005 and December 14, 2009. The rocket launch-produced disturbances arose 10 to 30 and 90 to 110 minutes after the launch. Recorded first was a negative perturbation of the electron density characterized by the average speed about 2 km/s. The next perturbation was a quasi-periodic one moving at a speed about 400 m/s. The magnitude of relative variations in the electron density reached 26 %.
DISPERSION PROPERTIES OF REFLECTING GRATING FILLED WITH METAMATERIAL
149-157
10.1615/RadioPhysicsRadioAstronomy.v3.i2.70
O.P.
Kusaykin
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine 12, Academician Proskura St., Kharkiv 61085, Ukraine
P.M.
Melezchik
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine 12, Academician Proskura St., Kharkiv 61085, Ukraine
S. B.
Panin
A. Usikov Institute for Radiophisics and Electronics Natonal Academy of Sciences of Ukraine 12, Academiccian Proskura St., Kharkov, 61085, Ukraine
A.Yu.
Poyedinchuk
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine 12, Academician Proskura St., Kharkiv 61085, Ukraine
metamaterial
periodic waveguide
frequency dispersion
Bragg reflection
surface and leaking waves
The decomposition method is employed to solve the spectral problem on propagation constants of TM-modes of the periodic waveguide produced by a rectangular-groove reflecting grating filled with metamaterial of negative permittivity. The characteristic behavior of the eigenwave dispersion dependences is theoretically studied through a wide range of waveguide parameters. It has been found that Bragg regimes may appear by varying the grating geometric parameters and metamaterial characteristic frequency.
MICROWAVE SPECTROSCOPY OF TORSION VIBRATIONS IN MOLECULES: APPROXIMATION OF STRICT COUPLING BETWEEN THE STRUCTURAL TORSIONAL PARAMETERS ρ AND F IN THE RHO AXIS METHOD
159-167
10.1615/RadioPhysicsRadioAstronomy.v3.i2.80
V. V.
Ilyushin
Institute of Radio Astronomy, National Academy of Sciences of Ukraine, 4, Chervonopraporna St., Kharkiv, 61002, Ukraine
Rho axis method
hindered internal rotation
microwave spectroscopy
torsion-rotation spectrum
In the paper, the approximation of strict coupling between the structural torsional parameters F and ρ in the Rho axis method and its applicability to analyzing the observed molecular spectra are considered for the molecules with methyl top hindered internal rotation. The functional relation between the F and ρ parameters which is implied in the rigid molecular structure approximation makes it possible to replace variation of these two parameters by variation of a single structural parameter, namely, of the moment of inertia of the C3υ group which is in torsion motion. The approximation in question has been verified through processing spectrum measurement data for a number of molecules which spectra have been analyzed in the literature using standard Rho axis method. It is shown that structural distortions in molecules with hindered internal rotation of the C3υ group, which are associated in the standard model of the Rho axis method with separate variation of the F and ρ parameters, are insignificant for the ground torsional state and can be accounted for through considering the fourth-order terms of the Hamiltonian in the course of fitting the spectra of excited torsional states.
MULTI-LOOK RADIOMETRIC CORRECTION OF SAR IMAGES
169-177
10.1615/RadioPhysicsRadioAstronomy.v3.i2.90
O. O.
Bezvesilniy
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
I. M.
Gorovyi
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
V. V.
Vinogradov
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
Dmitry M.
Vavriv
Institute of Radio Astronomy, National Academy of Sciences of Ukraine 4, Krasnoznamennaya St., Kharkiv 61002, Ukraine
synthetic aperture radar (SAR)
airborne SAR
radiometric errors
radiometric correction
multi-look processing
Deviations of the aircraft trajectory and instabilities of the aircraft orientation lead to non-uniform illumination of the ground by the antenna beam and, as a result, to radiometric errors in radar images obtained with airborne synthetic aperture radars (SAR). The clutter-lock technique is commonly used to avoid the radiometric errors. However, this approach leads to strong geometric distortions in SAR images in the case of fast and significant instabilities of antenna orientation. Here we propose a multi-look radiometric correction technique which can be used instead of the clutter-lock. The proposed approach has been tested by using a Ku-band airborne SAR system onboard light-weight aircraft.
UNSATURATED MODE AS ALTERNATIVE METHOD TO PROVIDE STABILITY OF LOW-NOISE AMPLIFIERS ON HIGH-ELECTRON-MOBILITY TRANSISTORS
179-185
10.1615/RadioPhysicsRadioAstronomy.v3.i2.100
A. M.
Korolev
Institute of Radio Astronomy, National Academy of Sciences of Ukraine, 4, Chervonopraporna St., Kharkiv, 61002, Ukraine
Valery M.
Shulga
Institute of Radio Astronomy of the National Academy of Sciences of Ukraine, Kharkov, Ukraine
HEMT
stability
low-noise
A new method to provide the stability of low-noise HEMT-based amplifiers is proposed. The method consists in goal-oriented selection of a DC mode in the unsaturated (ohmic) segment of current-voltage curve. Stability -primarily that out-of-band − rises without noise characteristic degradation. In support of the offered method efficiency, the results of examination of amplifiers designed on different transistors are brought.