An efficient near-to-far-field transformation (NTFFT) technique, wherein the near-field (NF) measurements are acquired along a planar spiral with a uniform step to make the control of the involved positioners easier, is developed in this article. Such a technique is tailored for quasi-spherical, i.e., volumetric, antennas under test and makes use of a reduced number of NF data. An effective two-dimensional sampling interpolation algorithm, allowing the accurate reconstruction of the input NF data for the standard NTFFT with plane-rectangular scan, is obtained by setting the spiral step equal to the sample spacing required for interpolating along a radial line according to the spatial bandlimitation properties of electromagnetic fields, and by properly developing a non-redundant representation along such a spiral. Tests results are reported to demonstrate that the proposed NTFFT technique retains the same accuracy as the standard plane-rectangular one.

中文翻译：

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从沿平面螺线以均匀步长收集的一组减少的近场样本简化构造体积AUT的远场模式

本文开发了一种有效的近场到远场变换（NTFFT）技术，其中沿平面螺旋线以均匀的步长获取近场（NF）测量值，从而使所涉及的定位器的控制更加容易。此类技术是针对拟测试中的准球形天线（即体积天线）量身定制的，并使用了数量减少的NF数据。通过将螺旋步长设置为等于沿着径向线进行插值所需的采样间隔，可以获得有效的二维采样插值算法，该算法允许使用平面矩形扫描为标准NTFFT准确重建输入NF数据。电磁场的空间带限特性，并通过沿着这种螺旋线适当发展非冗余表示。