Sanaz Kazemi

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Radio interferometric arrays as imperfect instruments require calibration to correct for instrumental gain and phase errors in observations. One point of calibration, our focus, is before the time-series of groups of compact receivers are beam-formed. Traditional supervised calibration approaches tune instrumental parameters using prior sky source(More)
Existing calibration algorithms in radio interferometry implicitly assume the noise to be Gaussian. However, outliers in the data due to interference or due to errors in the sky model would have adverse effects on processing based on a Gaussian noise model. Most of the shortcomings of calibration such as the loss in flux or coherence, and the appearance of(More)
In this paper, an efficient method to obtain the elements current distribution for a non uniformly spaced array is presented. For a given far field pattern, after sampling the array factor the proposed method uses the least mean square error technique to solve the system of equations rather than solving the previously published Legendre function method.(More)
The Square Kilometre Array (SKA) will form the largest radio telescope ever built and such a huge instrument in the desert poses enormous engineering and logistic challenges. Algorithmic and architectural breakthroughs are needed. Data is collected and processed in groups of antennas before transport for central processing. This processing includes(More)
Interferometric observations used in radio astronomy are affected by errors due to the propagation medium such as the ionosphere as well as by the instrument such as the beam shape. Hence, calibration of such observations is essential in order to produce high quality data suitable for scientific endeavors. Traditional calibration implicitly relies on an(More)
Image reconstruction techniques from signals received by sensors find application in several fields, including radio interferometry for astronomical investigations and magnetic resonance imaging for medical applications. This paper presents a novel method for image reconstruction based on the iterative scanning of a region of interest. A modified(More)
The new generation of radio synthesis arrays, such as Low Frequency Array and Square Kilometre Array, have been designed to surpass existing arrays in terms of sensitivity, angular resolution and frequency coverage. This evolution has led to the development of advanced calibration techniques that ensure the delivery of accurate results at the lowest(More)
Imaging techniques in radio interferometry often face a significant challenge posed by the large number of antenna signals received, from which the image information needs to be extracted. Beamforming is envisaged to reduce the rate required for transporting data from groups of antennas to a central site for further processing. We propose a novel method for(More)
Subtraction of compact, bright sources is essential to produce high quality images in radio astronomy. It is recently proposed that `clustered' calibration can perform better in subtracting fainter background sources. This is due to the fact that the effective power of a source cluster is greater than the power of an individual, weak source therefore(More)
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