Numerical Investigation of the System-Matrix Method for Higher-Order Probe Correction in Spherical Near-Field Antenna Measurements

The system-matrix method for higher-order probe correction in spherical near-field scanning is based on a renormalized least-squares approach in which the normal matrix closely resembles the identity matrix when most of the energy of the probe pattern resides in the first-order modes. This method will be "stressed-tested" in the present paper by employing probes for which up to 49% of the pattern energy resides in the higher-order modes. The condition number of the resulting normal matrix will be computed, and its "distance" from the identity matrix displayed. It is also shown how the condition number of the normal matrix can be further reduced.