Probe compensated near-field measurements: Basic theory, numerical techniques, accuracy

The general problem concerning the interaction of a measuring probe antenna with the near-field radiated by an arbitrary antenna is considered. The application of the Lorentz reciprocity theorem to the problem of determining the far-field pattern radiated by the antenna from the output of the probe when it is used to measure the near-field of the antenna over some specified surface is discussed. The probe compensation data required to correct for the directional effects of the probe, the effect of probe correction on the measured data, and the necessary mathematical computations are described. Modifications to the basic theory are described for the case of determining the far field receiving pattern of non-reciprocal antennas. The spatial sampling of the near field is discussed, and methods for filtering the data to reduce computer requirements are described. The calculated far-field patterns from specific near-field measurements are presented, and the accuracy of the calculated patterns is discussed.