Echo Reduction by Modal Filtering Technique in Advanced Near Field Antenna Measurement
Spurious error signals from absorbers and other structures in the measurement set-up can significantly decrease the measurement accuracy in standard antenna measurement configurations. In the majority of measurement cases with well-designed anechoic chambers, the measurement uncertainty contribution from these additional error signals named echo(s) or echo pollution in the following discussion can be considered negligible. However in special measurement conditions and/or when very high precision measurements are needed, the above consideration is no longer valid. Significant echo contributions can occur in the case of large angle of incidence even on absorber covered surfaces. Modal filtering is a flexible echo reduction approach purely based on intelligent post processing of measured data applicable to a wide range of antennas and measurements situations, such as Planar (PNF) Cylindrical (CNF) and Spherical Near Field (SNF), with no need for additional measurements or additional equipment.