A NTFF transformation method in planar near-field antenna measurement derived from FDTD

Focusing on the requirement of planar near-field antenna measurement, a method usually used in finite difference time domain simulation which is based on the equivalence theorem is employed in the process of near-to-far-field transformation. The distribution of the far-field pattern is obtained directly in polar spherical coordinate system. A standard gain horn antenna is taken as an example for testing. Near-field data, which are derived from theoretical formula and from numerical simulation, are transformed by this method. The results are compared with others obtained by traditional method based on plane wave spectrum expansion, analytical theory and electromagnetic computation with FDTD method. Finally, this method is proved to be reliable.