Near-field Extrapolation Study for Cylindrical Nearfield to Far-field Transformations

A Near-field (NF) extrapolation study for cylindrical near-field to far-field transformations is presented in this paper. The NF extrapolation techniques are studied in this work including the linear technique, nearest data technique, and piecewise cubic Hermite interpolating polynomial (PCHIP) technique, in order to reduce the effect of NF truncation data on FF antenna radiation pattern error. The cylindrical wave expansion with trapezoidal rule numerical integration is employed in the NF-FF transformation algorithm. In the study, NF data of the seven-patch array antenna is simulated by the commercial simulation program, where the NF sampling length of the cylindrical scan of 1.6 meters is employed. The NF extrapolation is applied to increase the NF sampling length of the cylindrical scan from 1.6 meters to 2.4 meters. It is found that the far side-lobe accuracy of AUT FF radiation patterns from the proposed technique using linear extrapolation is improved. The far side-lobe FF antenna radiation pattern error is reduced. The truncated scanning length of NF data provides less time-consuming NF data collection. The FF antenna radiation pattern error will be reduced by using appropriate NF extrapolation techniques.