NDLI: Incoherent clocking in coherent radio interferometers

Content Provider	IET Digital Library
Author	Carlson, B. R.
Abstract	Radio interferometer arrays are instruments requiring real-time synchronisation of all array elements to capture and align the observed source wavefront prior to further processing such as correlation and/or beamforming. One method is to deliver a frequency, from a common central local oscillator (LO), using a round-trip phase-stable distribution system such that each element has its own phase-stable copy of the clock with required real-time fidelity for down-conversion and digitisation. The method described here involves equipping each array element with its own independent ‘eLO’ and sending a ‘tracer’ of it to a central site, where the difference between the elements’ eLOs and the central ‘cLO’ is measured. The digitised data from each element is corrected at the central site according to the measurement, before correlation/beamforming. The advantage of this method is that only a ‘trace’ of eLO, needed to measure the rate of change of eLO relative to cLO integrated over a measurement interval, needs to be conveyed over this tracer link, rather than the frequency itself, thereby requiring lower link temporal fidelity and bandwidth.
Starting Page	909
Ending Page	911
Page Count	3
ISSN	00135194
Volume Number	54
e-ISSN	1350911X
Issue Number	Issue 14, Jul (2018)
Alternate Webpage(s)	https://digital-library.theiet.org/content/journals/el/54/14
Alternate Webpage(s)	https://digital-library.theiet.org/content/journals/10.1049/el.2018.0964
Journal	Electronics Letters
Publisher	The Institution of Engineering and Technology
Publisher Date	2018-06-06
Access Restriction	Open
Rights License	Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/)
Subject Keyword	Align The Observed Source Wavefront Antenna Array Array Element Array Signal Processing Capture Central CLO Central Site Clock Coherent Radio Interferometers Common Central Local Oscillator Correlation/beamforming Digitisation Digitised Data Down-conversion Element Incoherent Clocking Independent ELO Measurement Interval Optical, Image And Video Signal Processing Phase-stable Copy Radio Interferometer Array Radio Link And Equipment Radiofrequency Imaging Radiotelescopes Radiowave Interferometers Real-time Fidelity Real-time Synchronisation Round-trip Phase-stable Distribution System Signal Processing And Detection Synchronisation
Content Type	Text
Resource Type	Article
Subject	Electrical and Electronic Engineering

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in

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