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This paper presents a detailed evaluation of the envelope-tracking adaptive integral method (ET-AIM), an FFT-accelerated algorithm for analyzing electromagnetic scattering. ET-AIM is used to solve progressively more complex benchmark scattering problems and key parameters of the method (the auxiliary grid size, near-zone size, temporal basis function type, time-step size, and iterative solver tolerance) are optimized. The computational costs and accuracy of ET-AIM are compared to its time-domain counterpart, the time-domain adaptive integral method (TD-AIM), in the high-frequency regime, where the spatial discretization of the scattering object is determined by the minimum wavelength of interest rather than its geometrical features. Numerical results show that although ET-AIM and TD-AIM computation times are comparable when the bandwidth of interest is wide, the ET-AIM marching costs are dominated by iterative solution rather than scattered-field computations ('right-hand-side' computations) and that as the bandwidth of interest becomes narrower than 50% of the center frequency, ET-AIM computational costs become significantly smaller than TD-AIM ones. ET-AIM is also shown to efficiently solve large and complex scattering problems whose solution by TD-AIM is impractical. |
