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Improvement of the Digital Registering System for the Radio Emission in Spectral Lines

Transactions of IAA RAS, issue 53, 23–29 (2020)

Keywords: radio telescope, digital signals transformation, spectrum registration

Abstract

Problem. In the system for recording cosmic radio emission spectra in spectral lines the amplitudes of calculated power spectra components are calibrated with the noise temperature of the pilot signals. The pilot signals are generated by a modulated broadband noise generator (NG) and applied to the input of the receiving-amplifying channel of the radio telescope. For calibration the average noise temperature of calibration NG over a wide intermediate frequency (IF) range is used. The noise temperature of the calibration pulses is preliminarily measured by a radiometric device and is considered constant in a wide band of intermediate frequencies within which the tunable downconverter extracts the signal for investigation. But the actual noise temperatures spectrum of pilot signals experiences deviations from the nominal value due to the noise generator power fluctuations in a wide band and the irregularity of the generator coupling to the receiving channel in this band. These deviations can cause significant errors (up to 30–40 %) in determination of the amplitudes of signal power spectrum since the noise temperature of calibration pulse is used as a scaling factor. Aim. The aim of this work is to develop a method for eliminating errors in determination the amplitudes of spectral components of the narrowband signal, which are caused by calibration pulses power fluctuations in the IF band. Also the purpose of the work is to develop and test a spectrometric module for implementation of this method. Method. To eliminate errors in the amplitude calibration of the narrowband space radio emission spectra associated with the instability of the NGs power spectrum an additional channel for calculating the broadband spectrum is used. This channel is operating in parallel with the narrowband spectrum estimator. This makes it possible to measure the local variations of the NGs spectrum and take it into account when calculating the spectra of narrowband sources of cosmic radio emission. Result. The introduction of an additional channel for calculating the broadband power spectrum of noise pulses entering the narrowband radio emission registration system makes it possible to eliminate the influence of the fluctuations of pilot-signal pulses and significantly improve the accuracy of amplitude calibration of the signal spectrum under study and the quality of registration for weak irregularities of source emission.

Citation

Text

BibTeX

RIS

S. A. Grenkov, N. E. Kol’tsov. Improvement of the Digital Registering System for the Radio Emission in Spectral Lines // Transactions of IAA RAS. — 2020. — Issue 53. — P. 23–29.

@article{grenkov2020,
  abstract = {Problem. In the system for recording cosmic radio emission spectra in spectral lines the amplitudes of calculated power spectra components are calibrated with the noise temperature of the pilot signals. The pilot signals are generated by a modulated broadband noise generator (NG) and applied to the input of the receiving-amplifying channel of the radio telescope. For calibration the average noise temperature of calibration NG over a wide intermediate frequency (IF) range is used. The noise temperature of the calibration pulses is preliminarily measured by a radiometric device and is considered constant in a wide band of intermediate frequencies within which the tunable downconverter extracts the signal for investigation. But the actual noise temperatures spectrum of pilot signals experiences deviations from the nominal value due to the noise generator power fluctuations in a wide band and the irregularity of the generator coupling to the receiving channel in this band. These deviations can cause significant errors (up to 30–40 %) in determination of the amplitudes of signal power spectrum since the noise temperature of calibration pulse is used as a scaling factor.
Aim. The aim of this work is to develop a method for eliminating errors in determination the amplitudes of spectral components of the narrowband signal, which are caused by calibration pulses power fluctuations in the IF band. Also the purpose of the work is to develop and test a spectrometric module for implementation of this method.
Method. To eliminate errors in the amplitude calibration of the narrowband space radio emission spectra associated with the instability of the NGs power spectrum an additional channel for calculating the broadband spectrum is used. This channel is operating in parallel with the narrowband spectrum estimator. This makes it possible to measure the local variations of the NGs spectrum and take it into account when calculating the spectra of narrowband sources of cosmic radio emission.
Result. The introduction of an additional channel for calculating the broadband power spectrum of noise pulses entering the narrowband radio emission registration system makes it possible to eliminate the influence of the fluctuations of pilot-signal pulses and significantly improve the accuracy of amplitude calibration of the signal spectrum under study and the quality of registration for weak irregularities of source emission.},
  author = {S.~A. Grenkov and N.~E. Kol’tsov},
  doi = {10.32876/ApplAstron.53.23-29},
  issue = {53},
  journal = {Transactions of IAA RAS},
  keyword = {radio telescope, digital signals transformation, spectrum registration},
  pages = {23--29},
  title = {Improvement of the Digital Registering System for the Radio Emission in Spectral Lines},
  url = {http://iaaras.ru/en/library/paper/2046/},
  year = {2020}
}

TY  - JOUR
TI  - Improvement of the Digital Registering System for the Radio Emission in Spectral Lines
AU  - Grenkov, S. A.
AU  - Kol’tsov, N. E.
PY  - 2020
T2  - Transactions of IAA RAS
IS  - 53
SP  - 23
AB  - Problem. In the system for recording cosmic radio emission spectra in
spectral lines the amplitudes of calculated power spectra components
are calibrated with the noise temperature of the pilot signals. The
pilot signals are generated by a modulated broadband noise generator
(NG) and applied to the input of the receiving-amplifying channel of
the radio telescope. For calibration the average noise temperature of
calibration NG over a wide intermediate frequency (IF) range is used.
The noise temperature of the calibration pulses is preliminarily
measured by a radiometric device and is considered constant in a wide
band of intermediate frequencies within which the tunable
downconverter extracts the signal for investigation. But the actual
noise temperatures spectrum of pilot signals experiences deviations
from the nominal value due to the noise generator power fluctuations
in a wide band and the irregularity of the generator coupling to the
receiving channel in this band. These deviations can cause
significant errors (up to 30–40 %) in determination of the amplitudes
of signal power spectrum since the noise temperature of calibration
pulse is used as a scaling factor.  Aim. The aim of this work is to
develop a method for eliminating errors in determination the
amplitudes of spectral components of the narrowband signal, which are
caused by calibration pulses power fluctuations in the IF band. Also
the purpose of the work is to develop and test a spectrometric module
for implementation of this method.  Method. To eliminate errors in
the amplitude calibration of the narrowband space radio emission
spectra associated with the instability of the NGs power spectrum an
additional channel for calculating the broadband spectrum is used.
This channel is operating in parallel with the narrowband spectrum
estimator. This makes it possible to measure the local variations of
the NGs spectrum and take it into account when calculating the
spectra of narrowband sources of cosmic radio emission.  Result. The
introduction of an additional channel for calculating the broadband
power spectrum of noise pulses entering the narrowband radio emission
registration system makes it possible to eliminate the influence of
the fluctuations of pilot-signal pulses and significantly improve the
accuracy of amplitude calibration of the signal spectrum under study
and the quality of registration for weak irregularities of source
emission.
DO  - 10.32876/ApplAstron.53.23-29
UR  - http://iaaras.ru/en/library/paper/2046/
ER  -