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This paper describes methods for accurate pattern modeling of large axisymmetric paraboloidal focus-fed reflector antenna systems. We demonstrate that the incorporation of the developed pattern models helps in advancing the state-of-the-art in coherent time-domain canceling (CTC) for interference mitigation in radio astronomy. The first method yields a closed form expression for the antenna pattern with parameters accounting for the focal ratio and feed pattern. In subsequent adaptive methods, parameters of this model are calculated using measurements of interference signals. The corrected pattern model improves the prediction of the change in the true pattern for future times. The methods are compared by (1) comparing the error in the pattern model with respect to the true pattern and (2) comparing the pattern value update period required to achieve a specified level of residual interference when used in CTC. The efficacy of the pattern modeling methods is demonstrated by showing that the error in the pattern model decreases and the pattern value needs to be updated at a much slower rate for effective CTC. 

It has been recently demonstrated that modifying the rim scattering of a paraboloidal reflector antenna through the use of reconfigurable elements along the rim facilitates sidelobe modification including cancelling sidelobes. In this work we investigate techniques for determining the unit-magnitude weights (i.e., weights which modify the phase of the scattered signals) to accomplish sidelobe cancellation at arbitrary angles from the reflector axis. Specifically, it is shown that despite the large search space and the non-convexity of the cost function, weights can be found with reasonable complexity which provide significant cancellation capability. First, the optimal weights without any magnitude constraints are found. Afterwards, algorithms are developed for determining the unit-modulus weights with both quantized and unquantized phases. Further, it is shown that weights can be obtained that both cancel sidelobes while providing a constant main lobe gain. A primary finding is that sufficiently deep nulls are possible with essentially no change in the main lobe with practical (binary or quaternary) phase-only weights.