scholarly journals Calibration of Siberian Radioheliograph antenna gains using redundancy

2021 ◽  
Vol 7 (4) ◽  
pp. 98-103
Author(s):  
Mariia Globa ◽  
Sergey Lesovoi
Keyword(s):  
Antenna Array ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
High Dynamic Range ◽  
Special Care ◽  
System Of Equations ◽  
Signal To Noise ◽  
Double Step ◽  
Phase Calibration ◽  
High Dynamic

The paper describes application of standard gain calibration using redundancy for a 48-antenna prototype of Siberian Radioheliograph. Traditionally, for calibration, the visibilities were measured only between adjacent antennas since they have the highest signal-to-noise ratio and are sufficient for phase calibration. We have shown that this limited set of visibilities did not allow using the antenna array redundancy potential and obtaining images with a high dynamic range on a permanent basis. Images without amplitude calibration contain many artifacts and require special care when analyzed. The inclusion of visibility measurement between antennas with a double step made it possible to significantly increase the accuracy of solving the system of equations for amplitudes. Images constructed using both phase and amplitude calibrations do not have visible artifacts and are more reliable.

scholarly journals Calibration of Siberian Radioheliograph antenna gains using redundancy

2021 ◽  
Vol 7 (4) ◽  
pp. 104-110
Author(s):  
Mariia Globa ◽  
Sergey Lesovoi
Keyword(s):  
Antenna Array ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
High Dynamic Range ◽  
Special Care ◽  
System Of Equations ◽  
Signal To Noise ◽  
Double Step ◽  
Phase Calibration ◽  
High Dynamic

The paper describes application of standard gain calibration using redundancy for a 48-antenna prototype of Siberian Radioheliograph. Traditionally, for calibration, the visibilities were measured only between adjacent antennas since they have the highest signal-to-noise ratio and are sufficient for phase calibration. We have shown that this limited set of visibilities did not allow using the antenna array redundancy potential and obtaining images with a high dynamic range on a permanent basis. Images without amplitude calibration contain many artifacts and require special care when analyzed. The inclusion of visibility measurement between antennas with a double step made it possible to significantly increase the accuracy of solving the system of equations for amplitudes. Images constructed using both phase and amplitude calibrations do not have visible artifacts and are more reliable.

A signal-to-noise ratio comparison of high dynamic range CMOS image sensors

2009 ◽  
Author(s):  
Leo H. C. Braga ◽  
Suzana Domingues ◽  
José G. Gomes ◽  
Antonio C. Mesquita
Keyword(s):  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
High Dynamic Range ◽  
Image Sensors ◽  
Signal To Noise ◽  
Cmos Image Sensors ◽  
High Dynamic ◽  
Noise Ratio

scholarly journals High Dynamic Range and the Search for Planets

2003 ◽  
Vol 211 ◽  
pp. 487-496 ◽  
Author(s):  
A. T. Tokunaga ◽  
C. Ftaclas ◽  
J. R. Kuhn ◽  
P. Baudoz
Keyword(s):  
Adaptive Optics ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
Stray Light ◽  
Strehl Ratio ◽  
Fabrication Technology ◽  
Signal To Noise ◽  
High Dynamic ◽  
Differential Imaging ◽  
Adaptive Optics System

General arguments for optimized coronagraphy in the search for planets are presented. First, off-axis telescopes provide the best telescopic platforms for use with coronagraphy, and telescope fabrication technology now allows the fabrication of such telescopes with diameters of up to 6.5 m. We show that in certain circumstances a smaller telescope with an off-axis primary has a signal-to-noise advantage compared with larger Cassegrain telescopes. Second, to fully exploit the advantages of the coronagraph for suppressing stray light, it is necessary to use a high Strehl ratio adaptive optics system. This can be best achieved initially with modest aperture telescopes of 3–4 m in diameter. Third, application of simultaneous differential imaging and simultaneous polarimetric techniques are required to reach the photon-limit of coronagraphic imaging. These three developments, if pursued together, will yield significant improvements in the search for planets.

Calibration method for large-aperture digital antenna array

2019 ◽  
pp. 37-44
Author(s):  
Yu. A. Shishov ◽  
D. V. Gubanov ◽  
M. G. Vahlov ◽  
V. M. Balashov
Keyword(s):  
Antenna Array ◽  
Early Warning ◽  
Dynamic Range ◽  
Pulse Sequence ◽  
Signal To Noise Ratio ◽  
Radio Pulse ◽  
Calibration Method ◽  
Signal To Noise ◽  
Large Aperture ◽  
Technical Solutions

Вased on the analysis of known technical solutions, the article proposes a method for calibrating the large-aperture receiving AESA radar for early warning. The peculiarity of this technique is that a coherent radio pulse sequence is applied as the calibration signal supplied to the inputs of the receiving modules. The power of each of the radio pulses is of the same order as the power of the signals arriving at the inputs of the receiving modules when the radar is operating normally, that is, with the signal-to-noise ratio at the input of the AFAR receiving module of 10-6-10-3. Thus, the calibration should occur in the region of small signals, within the working dynamic range. The technical implementation of this technique allows to obtain a higher accuracy of the calibration of the AESA while simplifying the design of the receiving modules, compared with similar technical solutions.

scholarly journals Probing delayed-end reionization histories with the 21-cm LAE cross-power spectrum

2020 ◽  
Vol 494 (1) ◽  
pp. 703-718 ◽  
Author(s):  
Lewis H Weinberger ◽  
Girish Kulkarni ◽  
Martin G Haehnelt
Keyword(s):  
Power Spectrum ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
High Dynamic Range ◽  
Integration Time ◽  
Signal To Noise ◽  
Total Signal ◽  
The Cross ◽  
Noise Ratio ◽  
Cross Power Spectrum

ABSTRACT We model the 21-cm signal and Lyman-α emitter (LAE) population evolution during the epoch of reionization in order to predict the 21-cm LAE cross-power spectrum. We employ high-dynamic-range simulations of the intergalactic medium to create models that are consistent with constraints from the cosmic microwave background, Lyman-α forest, and LAE population statistics. Using these models we consider the evolution of the cross-power spectrum for a selection of realistic reionization histories and predict the sensitivity of current and upcoming surveys to measuring this signal. We find that the imprint of a delayed end to reionization can be observed by future surveys, and that strong constraints can be placed on the progression of reionization as late as z = 5.7 using a Subaru–SKA survey. We make predictions for the signal-to-noise ratios achievable by combinations of Subaru/PFS (Prime Focus Spectrograph) with the MWA, LOFAR, HERA, and SKA interferometers for an integration time of 1000 h. We find that a Subaru–SKA survey could measure the cross-power spectrum for a late reionization at z = 6.6 with a total signal-to-noise ratio greater than 5, making it possible to constrain both the timing and bubble size at the end of reionization. Furthermore, we find that expanding the current Subaru/PFS survey area and depth by a factor of three would double the total signal-to-noise ratio.

scholarly journals Simultaneous High Dynamic Range Algorithm, Testing, and Instrument Simulation

2022 ◽  
Vol 924 (2) ◽  
pp. 63
Author(s):  
James Paul Mason ◽  
Daniel B. Seaton ◽  
Andrew R. Jones ◽  
Meng Jin ◽  
Phillip C. Chamberlin ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
High Dynamic Range ◽  
Mission Design ◽  
Single Exposure ◽  
A Value ◽  
Varied Duration ◽  
High Dynamic ◽  
Mass Ejection ◽  
Bright Emission

Abstract Within an imaging instrument’s field of view, there may be many observational targets of interest. Similarly, within a spectrograph’s bandpass, there may be many emission lines of interest. The brightness of these targets and lines can be orders of magnitude different, which poses a challenge to instrument and mission design. A single exposure can saturate the bright emission and/or have a low signal-to-noise ratio (S/N) for faint emission. Traditional high dynamic range (HDR) techniques solve this problem by either combining multiple sequential exposures of varied duration or splitting the light to different sensors. These methods, however, can result in the loss of science capability, reduced observational efficiency, or increased complexity and cost. The simultaneous HDR method described in this paper avoids these issues by utilizing a special type of detector whose rows can be read independently to define zones that are then composited, resulting in areas with short or long exposure measured simultaneously. We demonstrate this technique for the Sun, which is bright on disk and faint off disk. We emulated these conditions in the lab to validate the method. We built an instrument simulator to demonstrate the method for a realistic solar imager and input. We then calculated S/Ns, finding a value of 45 for a faint coronal mass ejection and 200 for a bright one, both at 3.5  ⊙ N —meeting or far exceeding the international standard for digital photography that defines an S/N of 10 as acceptable and 40 as excellent. Future missions should consider this type of hardware and technique in their trade studies for instrument design.

scholarly journals Spherical logarithmic quantization and its application for DPCM

2004 ◽  
Vol 17 (2) ◽  
pp. 165-184 ◽  
Author(s):  
Johannes Huber ◽  
Bernd Matschkal
Keyword(s):  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Rate Distortion ◽  
Differential Pulse ◽  
High Dynamic Range ◽  
Pulse Code Modulation ◽  
Signal To Noise ◽  
Differential Pulse Code Modulation ◽  
Source Signal ◽  
Noise Ratio

A new method for efficient digitizing analog signals while preserving the original waveform as close as possible with respect to the relative quantization error is presented. Logarithmic quantization is applied to short vectors of samples represented in sphere coordinates. The resulting advantages, i.e. a constant Signal-to-Noise Ratio over a very high dynamic range at a small loss with respect to rate-distortion theory are discussed. In order to increase the Signal-to-Noise Ratio (SNR) by exploitation of correlations within the source signal, a method of combining differential pulse code modulation (DPCM) with spherical logarithmic quantization is presented. The resulting technique achieves an efficient digital representation of waveforms with a high long term as well as segmental SNR at an extreme low delay of the signal.

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