Karl F. Warnick, Marianna Ivashina, Stefan Wijnholds and Rob Maaskant, "Beamforming, Calibration and Figures of Merit for Polarimetric Phased Array Antennas", IEEE International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting, Spokane (USA), 3-8 July 2011

abstract: Several major efforts are underway worldwide to replace traditional single pixel radio astronomy instruments with wide-field, multipixel phased array feeds and aperture arrays. For phased array antennas, one critical open area of research is the calibration and beamforming algorithms required for the multi-pixel signal processing and image formation. Since science applications of these instruments rely heavily on the polarization properties of astronomical sources, calibration and beamforming algorithms for phased array antennas must include methods for producing stable, well-characterized beams with high polarimetric accuracy.
This presentation will develop a system model for a polarimetric phased array, adapt the IEEE standard figures of merit for polarimetric accuracy to beamforming arrays, derive the optimal beamforming solution considering both receiver sensitivity (G/T) and polarimetric accuracy, and present a practical calibration and beamforming method using bright sky point sources. Numerical results for a phased array feed antenna will be given to illustrate the performance of the practical method relative to the optimal solution.

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