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## Delay Stability in Digital Backends of VLBI Radio Telescopes

Transactions of IAA RAS, issue 49, 52–59 (2019)

Keywords: delay stability, instrumental delay, VLBI, radio telescope, digital backend, Multifunctional Digital Backend, Broadband Acquisition System

### Abstract

Achieving picoseconds delay accuracy in VLBI observations requires control-ling the variations of instrumental delay on the level of 1 picosecond or better in each scan. Instability in electronic devices is significantly related to temperature variations, therefore it is necessary to reduce temperature sensitivity of the equipment and stabilize the temperature where possible. The remaining variations of instrumental delay should be measured and taken into account during the processing. The paper overviews instability sources in VLBI digital backends and provides the corresponding delay temperature coefficients, as well as the ways to reduce them. It also describes embedded calibration system for measuring internal delay variations in the Multifunctional Digital Backend developed in IAA RAS.

### Citation

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E. V. Nosov, A. S. Berdnikov, D. A. Marshalov. Delay Stability in Digital Backends of VLBI Radio Telescopes // Transactions of IAA RAS. — 2019. — Issue 49. — P. 52–59. @article{nosov2019, abstract = {Achieving picoseconds delay accuracy in VLBI observations requires control-ling the variations of instrumental delay on the level of 1 picosecond or better in each scan. Instability in electronic devices is significantly related to temperature variations, therefore it is necessary to reduce temperature sensitivity of the equipment and stabilize the temperature where possible. The remaining variations of instrumental delay should be measured and taken into account during the processing. The paper overviews instability sources in VLBI digital backends and provides the corresponding delay temperature coefficients, as well as the ways to reduce them. It also describes embedded calibration system for measuring internal delay variations in the Multifunctional Digital Backend developed in IAA RAS.}, author = {E.~V. Nosov and A.~S. Berdnikov and D.~A. Marshalov}, doi = {10.32876/ApplAstron.49.52-59}, issue = {49}, journal = {Transactions of IAA RAS}, keyword = {delay stability, instrumental delay, VLBI, radio telescope, digital backend, Multifunctional Digital Backend, Broadband Acquisition System}, pages = {52--59}, title = {Delay Stability in Digital Backends of VLBI Radio Telescopes}, url = {http://iaaras.ru/en/library/paper/1968/}, year = {2019} } TY - JOUR TI - Delay Stability in Digital Backends of VLBI Radio Telescopes AU - Nosov, E. V. AU - Berdnikov, A. S. AU - Marshalov, D. A. PY - 2019 T2 - Transactions of IAA RAS IS - 49 SP - 52 AB - Achieving picoseconds delay accuracy in VLBI observations requires control-ling the variations of instrumental delay on the level of 1 picosecond or better in each scan. Instability in electronic devices is significantly related to temperature variations, therefore it is necessary to reduce temperature sensitivity of the equipment and stabilize the temperature where possible. The remaining variations of instrumental delay should be measured and taken into account during the processing. The paper overviews instability sources in VLBI digital backends and provides the corresponding delay temperature coefficients, as well as the ways to reduce them. It also describes embedded calibration system for measuring internal delay variations in the Multifunctional Digital Backend developed in IAA RAS. DO - 10.32876/ApplAstron.49.52-59 UR - http://iaaras.ru/en/library/paper/1968/ ER -