Comparison of APC and Feed-APC using field Probing measurements of the Quiet Zone

In antenna measurements Antenna Pattern Comparison (APC) and Feed-APC can be used to negate the effect of residual amplitude and phase ripple in the QZ. Although the processing of the measurement data using APC or Feed-APC of the measured antenna pattern in a compact antenna measurement range (CATR) environment is similar, their impact on the Quiet Zone (QZ) quality is quite different. For the APC case only the Antenna under Test (AUT) positioning system changes its location and therefore also only reflections caused by the AUT positioning system differ, which has a low impact on the QZ behaviour in general. For Feed-APC however the averaging is achieved by changing the angle of the QZ illumination by moving the feed, which also causes a change in the illumation of the main reflection points. This paper will present the impact of both APC and Feed-APC on the quality of the QZ. The improvements are shown without any dependency on a given antenna pattern by comparing the resulting QZ field distribution which are measured using Field Probing.