Near-Field Experimental Verification of the EM Models for the LOFAR Radio Telescope

Modern radio astronomical facilities in the Very High-Frequency band (VHF, 30-300 MHz) consist of large antenna arrays with digital beamforming. The calibration of these instruments requires accurate models of their electromagnetic behavior. Numerical models covering the full telescope field-of-view...

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Bibliographic Details
Published in:IEEE antennas and wireless propagation letters 2018-04, Vol.17 (4), p.613-616
Main Authors: Bolli, Pietro, Pupillo, Giuseppe, Paonessa, Fabio, Virone, Giuseppe, Wijnholds, Stefan J., Lingua, Andrea Maria
Format: Article
Language:English
Subjects:
Antenna measurements
antenna radiation patterns
Extraterrestrial measurements
near fields
Phased arrays
Radio astronomy
Telescopes
Unmanned aerial vehicles
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Summary:Modern radio astronomical facilities in the Very High-Frequency band (VHF, 30-300 MHz) consist of large antenna arrays with digital beamforming. The calibration of these instruments requires accurate models of their electromagnetic behavior. Numerical models covering the full telescope field-of-view are nowadays effectively computed by means of full-wave solvers. However, their experimental verification is still an open and challenging task. This letter proposes a verification strategy based on near-field scans. An unmanned aerial vehicle carrying a test source is used to excite the array from a limited set of spatial points, located in the radiating near-field region. The collected data are directly used to verify the telescope electromagnetic model without additional postprocessing. This exploits the capability of full-wave solvers to predict near-field patterns from the same geometrical and electrical model used to compute far-field patterns. The application of the proposed technique to the Low Frequency Array (LOFAR) radio telescope verified the predictions with residuals below 0.5 dB.
ISSN:1536-1225
1548-5757
DOI:10.1109/LAWP.2018.2805999