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Prediction of Aperture Efficiency Ripple in Clear Aperture Offset Gregorian Antennas

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1 Author(s)
de Villiers, D.I.L. ; Dept. of Electr. & Electron. Eng., Stellenbosch Univ., Stellenbosch, South Africa

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.

Published in:

Antennas and Propagation, IEEE Transactions on  (Volume:61 ,  Issue: 5 )