Prediction of aperture efficiency ripple in clear aperture offset Gregorian antennas
CITATION: De Villiers, D. I. L. 2013. Prediction of aperture efficiency ripple in clear aperture offset Gregorian antennas. IEEE Transactions on Antennas and Propagation, 61(5):2457-2465, doi: 10.1109/TAP.2013.2239953.
The original publication is available at http://ieeexplore.ieee.org
ENGLISH ABSTRACT: Electrically small clear aperture dual offset reflector systems often exhibit a directivity ripple over frequency due to the interference of the diffracted field from the sub-reflector with the main beam field. This paper investigates the cause of the ripple, and presents a technique to predict the expected system directivity, including the ripple, using the feed radiation pattern augmented by an efficient simulation strategy in a clear aperture offset Gregorian system. The method allows for accurate prediction of the directivity ripple using a severely under-sampled set of simulation results. Predicted results are compared to several simulations, and agreement to better than 0.5 % is found for the majority of configurations using both analytical and full wave simulated feed patterns.
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