Calibrated time-domain nearfield-immunity test on printed-circuit board level

Field-immunity scanning with small field probes closely above printed-circuit boards allows localizing sensitive circuit areas with high resolution. For quantifying the sensitivity level and to assure repeatable results a suitable calibration method is presented. In contrast to recent approaches based on the forward power supplied to the probe, this paper presents an accurate method using a mini-TEM cell, which allows adjusting the desired field strength at a selected distance. As an extension to previous work restricted to CW signals, in this paper it is shown how the calibration can be performed for arbitrary transient noise signals. Validation is carried out by an exact field-simulation of the near-field coupling into a signal trace. As an application example the Bit Error Ratio (BER) of a simple digital data transmission subject to a trapezoidal noise signal is investigated, depending on repetition rate, probe position and field strength.