The advantages of spatial domain probe compensation technique in EMC near-field measurements

Electromagnetic Compatibility (EMC) is a challenging task in today´s highly developed electronics. Near-field scanning provides an insight into the physical behavior of circuits and thus allows understanding the problems. Therefore, near-field scanning enables a well-directed optimization regarding EMC in electronic systems. It is a thorough task to gain the electric and magnetic fields from the measured probe signals, especially in the context of EMC. Even small field amplitudes are critical. So, the sensitivity of the probe is decisive and due to that the minimum probe size is limited. For this reason the fields across the probe are not homogenous. Then, probe compensation by means of an antenna factor is not sufficient. The common probe compensation technique is based on the plane wave theory. It is well known in literature. Some papers on the optimization are available. However, this technique has one significant disadvantage: truncation errors. Due to that the scanning area has to be very large and without any holes. This is achievable with small test structures having no protruding components, but not with most of the circuits in real applications. This paper presents a promising alternative: Probe compensation in the spatial domain by means of least square algorithms.