B. S. GIRISH
Articles written in Journal of Astrophysics and Astronomy
Volume 38 Issue 1 March 2017 Article ID 0011 Review Article
The Receiver System for the Ooty Wide Field Array
C. R. Subrahmanya P. Prasad B. S. Girish R. Somashekar P. K. Manoharan A. K. Mittal
The legacy Ooty Radio Telescope (ORT) is being reconfigured as a 264-element synthesis telescope, called the Ooty Wide Field Array (OWFA). Its antenna elements are the contiguous 1.92 m sections of the parabolic cylinder. It will operate in a 38-MHz frequency band centred at 326.5 MHz and will be equipped with a digital receiver including a 264-element spectral correlator with a spectral resolution of 48 kHz. OWFA is designed to retain the benefits of equatorial mount, continuous 9-hour tracking ability and large collecting area of the legacy telescope and use of modern digital techniques to enhance the instantaneous field-of-view by more than an order of magnitude. OWFA has unique advantages for contemporary investigations related to large scale structure, transient events and space weather watch. In this paper, we describe the RF subsystems, digitizers and fibre optic communication of OWFA and highlight some specific aspects of the system relevant for the observations planned during the initial operation.
Volume 44 All articles Published: 9 February 2023 Article ID 0011 TECHNICAL REVIEW
High-performance computing for SKA transient search: Use of FPGA-based accelerators
R. AAFREEN R. ABHISHEK B. AJITHKUMAR ARUNKUMAR M. VAIDYANATHAN INDRAJIT V. BARVE SAHANA BHATTRAMAKKI SHASHANK BHAT B. S. GIRISH ATUL GHALAME Y. GUPTA HARSHAL G. HAYATNAGARKAR P. A. KAMINI A. KARASTERGIOU L. LEVIN S. MADHAVI M. MEKHALA M. MICKALIGER5 V. MUGUNDHAN ARUN NAIDU J. OPPERMANN B. ARUL PANDIAN N. PATRA A. RAGHUNATHAN JAYANTA ROY SHIV SETHI B. SHAW K. SHERWIN O. SINNEN S. K. SINHA K. S. SRIVANI B. STAPPERS C. R. SUBRAHMANYA THIAGARAJ PRABU C. VINUTHA Y. G. WADADEKAR HAOMIAO WANG C. WILLIAMS
This paper presents high-performance computing efforts with FPGA for the accelerated pulsar/transient search for the square kilometre array (SKA). Case studies are presented from within SKA and pathfinder telescopes highlighting future opportunities. It reviews the scenario that has shifted from offline processing of the radio telescope data to digitizing several hundreds/thousands of antenna outputs over huge bandwidths, forming several hundreds of beams, and processing the data in the SKA real-time pulsar search pipelines. A briefaccount of the different architectures of the accelerators, primarily, the new generation field programmable gate array-based accelerators, showing their critical roles to achieve high-performance computing and in handlingthe enormous data volume problems of the SKA is presented here. It also presents power-performance efficiency of this emerging technology and presents potential future scenarios.
Volume 44 All articles Published: 31 March 2023 Article ID 0028 TECHNICAL REVIEW
Progression of digital-receiver architecture: From MWA to SKA1-Low, and beyond
B. S. GIRISH S. HARSHAVARDHAN REDDY SHIV SETHI K. S. SRIVANI R. ABHISHEK B. AJITHKUMAR SAHANA BHATTRAMAKKI KAUSHAL BUCH SANDEEP CHAUDHURI YASHWANT GUPTA P. A. KAMINI SANJAY KUDALE S. MADHAVI MEKHALA MULEY T. PRABU AGARAM RAGHUNATHAN G. J. SHELTON
Backed by advances in digital electronics, signal processing, computation and storage technologies, aperture arrays, which had strongly influenced the design of telescopes in the early years of radio astronomy, havemade a comeback. Amid all these developments, an international effort to design and build the world’s largest radio telescope, the Square Kilometre Array (SKA), is ongoing. With its vast collecting area of 1 km$^2$, the SKA is envisaged to provide unsurpassed sensitivity and leverage technological advances to implement a complex receiver to provide a large field of view through multiple beams on the sky. Many pathfinders and precursor aperture array telescopes for the SKA, operating in the frequency range of 10–300 MHz, have been constructed and operationalized to obtain valuable feedback on scientific, instrumental and functional aspects. This review article looks explicitly into the progression of digital-receiver architecture from the Murchison Widefield Array(precursor) to the SKA1-Low. It highlights the technological advances in analog-to-digital converters (ADCs), field-programmable gate arrays (FPGAs) and central processing unit–graphics processing unit (CPU–GPU) hybrid platforms around which complex digital signal processing systems implement efficient channelizers, beamformers and correlators. The article concludes with a preview of the design of a new generation signal processing platform based on radio frequency system-on-chip (RFSoC).
Volume 44 All articles Published: 10 May 2023 Article ID 0043 TECHNICAL REVIEW
Antennas for low-frequency radio telescope of SKA
AGARAM RAGHUNATHAN KEERTHIPRIYA SATISH ARASI SATHYAMURTHY T. PRABU B. S. GIRISH K. S. SRIVANI SHIV K. SETHI
The low-frequency radio telescope of the Square Kilometre Array (SKA) is being built by the international radio astronomical community to (i) have orders of magnitude higher sensitivity and (ii) be able to map the sky several hundred times faster, than any other existing facilities over the frequency range of 50–350MHz. The sensitivity of a radio telescope array is in general, dependent upon the number of electromagnetic sensors used to receive the sky signal. The total number of them is further constrained by the effects of mutual coupling between the sensor elements, allowable grating lobes in their radiation patterns, etc. The operating frequency band is governed by the desired spatial and spectral responses, acceptable sidelobe and backlobe levels, radiation efficiency, polarization purity and calibratability of sensors’ response. This paper presents abrief review of several broadband antennas considered as potential candidates by various engineering groups across the globe, for the low-frequency radio telescope of SKA covering the frequency range of 50–350 MHz, on the basis of their suitability for conducting primary scientific objectives.
Volume 44, 2023
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