The number of truncation in circular near-field to far-field transformation method

It is crucial to choose the appropriate number of truncation in circular near-field to far-field transformation (CNFFFT)
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. The accuracy of transformation would be inaccurate if the number of truncation is lack; There would be unnecessary cost calculation, on the other hand, if the number of truncation is too much. In this paper, the number of truncation in circular near-field to far-field transformation method is investigated. Firstly, the relationship of power spectrum and the number of truncation is acquired by Fourier Transform to process near-field scattering data. Secondly, the extrapolated results of different number of truncation are compared, where the number of truncation is chosen by the power spectrum. In this way, the appropriate number of truncation would be defined. The simulation result proves that it is proper to choose the number of truncation when the normalized power spectrum is reduced to -40dB.