scholarly journals Suppressing non-local effects due to Doppler frequency shifts in dynamic Brillouin fiber sensors

2020 ◽  
Vol 28 (8) ◽  
pp. 10760 ◽  
Author(s):  
Joseph B. Murray ◽  
Brandon Redding
Keyword(s):  
Doppler Frequency ◽  
Local Effects ◽  
Frequency Shifts ◽  
Fiber Sensors ◽  
Non Local ◽  
Doppler Frequency Shifts

scholarly journals Исследования альфвеновских мод на токамаке Глобус-М2 с использованием многочастотного допплеровского рефлектометра V-диапазона

2021 ◽  
Vol 47 (4) ◽  
pp. 41
Author(s):  
В.В. Буланин ◽  
И.М. Балаченков ◽  
В.И. Варфоломеев ◽  
В.К. Гусев ◽  
Г.С. Курскиев ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Doppler Frequency ◽  
Spherical Tokamak ◽  
Frequency Shifts ◽  
Toroidal Plasma ◽  
V Band ◽  
New Information ◽  
Spectral Components ◽  
Central Regions ◽  
Doppler Frequency Shifts

New information on the development of Alfvén modes in the Globus-M2 spherical tokamak is presented. The data were obtained using a V-band Doppler reflectometer with probing radiation frequencies from 50 to 75 GHz. A microwave harmonic synthesizer was used as a multifrequency probing source. As a result of using a new reflectometer, the localization of the toroidal Alfvén eigenmode has been determined at a magnetic field of 0.5 T. The spectral components of the Alfvén mode with Doppler frequency shifts due to toroidal plasma rotation have been recorded. The so-called Alfvén cascades have been investigated in the central regions of the discharge.

THE OCCURRENCE AND CHARACTERISTICS OF RADAR AURORAL ECHOES AT 488 AND 944 MC/S

1963 ◽  
Vol 41 (8) ◽  
pp. 1359-1380 ◽  
Author(s):  
B. C. Blevis ◽  
J. W. B. Day ◽  
O. S. Roscoe
Keyword(s):  
Specular Reflection ◽  
Doppler Frequency ◽  
Ground Level ◽  
Wavelength Dependence ◽  
Magnetic Disturbance ◽  
Frequency Data ◽  
Scattering Medium ◽  
Night Time ◽  
Frequency Shifts ◽  
Doppler Frequency Shifts

Radar backscatter observations of auroral ionization have been made from Ottawa on two similar systems operating at 488 and 944 Mc/s. These systems, as nearly scaled as was practicable, were operated almost continuously during the period from May 1959 to April 1961, inclusive.Narrow-beam transmitting and receiving antennas were used. They were each fixed in position to intercept the ionosphere at auroral heights in the region where the orthogonality condition for specular reflection is most nearly satisfied. A magnetometer recorded the magnetic disturbance at ground level at a point under the echoing region. Measurements were made of the time, amplitude, range, and frequency spectrum of the auroral echoes on each of the two frequencies, at both the transmitted and orthogonal polarizations.The data obtained indicate a double-peaked night time maximum in the occurrence of auroral echoes. A slight but distinct minimum appears just before local midnight. Equinoctial maxima are observed in the seasonal variation. The probability of occurrence of echoes increases rapidly with increasing magnetic disturbance. The average Doppler frequency shift of the echoes exhibits a systematic diurnal variation. There is a reversal in the direction of apparent motions, coincident with a change in sign of the average magnetic disturbance, and occurring at about the same time as the night time minimum in occurrence. From the two frequency data, echo cross section is found to vary as about the seventh power of the wavelength. There is no distinct evidence of depolarization or rotation of the plane of polarization of the echoes.Observations of the Doppler frequency shifts are interpreted in terms of the motions of auroral ionization. The wavelength dependence of auroral echoes is used to infer certain properties of the scattering medium.

An Experiment on Radio Location of Objects in the Near-Earth Space with VLBI in 2012

2013 ◽  
Vol 22 (1) ◽  
Author(s):  
M. Nechaeva ◽  
A. Antipenko ◽  
V. Bezrukovs ◽  
D. Bezrukov ◽  
A. Dementjev ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Space Debris ◽  
Rotation Period ◽  
Doppler Frequency ◽  
Radio Telescopes ◽  
Frequency Shifts ◽  
Near Earth Space ◽  
Vlbi Data ◽  
Doppler Frequency Shifts ◽  
Radio Location

AbstractAn experiment on radar location of space debris objects using of the method of VLBI was carried out in April, 2012. The radar VLBI experiment consisted in irradiation of some space debris objects (4 rocket stages and 5 inactive satellites) with a signal of the transmitter with RT-70 in Evpatoria, Ukraine. Reflected signals were received by a complex of radio telescopes in the VLBI mode. The following VLBI stations took part in the observations: Ventspils (RT-32), Urumqi (RT-25), Medicina (RT-32) and Simeiz (RT-22). The experiment included measurements of the Doppler frequency shift and the delay for orbit refining, and measurements of the rotation period and sizes of objects by the amplitudes of output interferometer signals. The cross-correlation of VLBI-data is performed at a correlator NIRFI-4 of Radiophysical Research Institute (Nizhny Novgorod). Preliminary data processing resulted in the series of Doppler frequency shifts, which comprised the information on radial velocities of the objects. Some results of the experiment are presented.

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