In this work, a novel use of the Non-Uniform Fast Fourier Transform (NUFFT) in reflectarray antenna analysis is proposed to greatly accelerate the computation of radiation patterns using a nonuniform, reduced and adaptive grid in the spectral domain. The proposed methodology is very useful for very large reflectarrays, which have very narrow beamwidths due to their large directivity, and shaped-beam reflectarrays for satellite applications such as Direct Broadcast Satellite (DBS), which might require a compliance analysis in very small angular regions. In those cases, high resolution in the radiation pattern is required, while a low resolution could be enough elsewhere to account for side lobes. However, current analysis techniques for such reflectarrays present limitations regarding large memory footprints or slow computations. The methodology presented in this work allows to overcome those limitations by performing computations in a non-uniform, reduced and adaptive grid in the transformed UV domain, achieving faster computations using considerably less memory. Numerical examples for current applications of interest are provided to assess the capabilities of the technique. In particular, the use of the NUFFT allows to compute efciently the radiation pattern in any principal plane with improved resolution for multibeam applications. Also, compliance analyses for DBS applications may be improved with the use of a reduced, multiresolution grid and the NUFFT. The proposed technique is thus suitable to greatly accelerate optimization algorithms.
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