Improving Near-Field Probe Calibration Technique for Immunity Tests at PCB Level

Near-field scan immunity (NFSI) enables localised and controlled field injection, making it a powerful technique for assessing the vulnerability of electronic components to radio frequency directed energy weapons. However, the lack of rigorous probe calibration methods currently limits its use to qualitative analysis. This article introduces a complete calibration workflow for electric and magnetic near-field (NF) injection probes, based on the equivalent dipole assumption. The method quantifies both the main and parasitic field components and establishes the spatial and frequency range over which the dipole model remains valid. This characterization enables the quantitative prediction of field-to-line coupling, through simulation or analytical models, when the properties of the trace and the component impedance are known. The proposed approach provides a necessary foundation for making NFSI a quantitative tool for immunity analysis. Experimental validations on various probes and printed circuit board traces support the methodology and demonstrate its practical relevance.