Test Design Methodology for Time-Domain Immunity Investigations Using Electric Near-Field Probes

This article investigates the possibility to develop time-domain immunity tests using electric near-field probes, for flexible customization of broadband input waveforms injected into specific pins of PCBs. For this purpose, a test design methodology is proposed, which is based on circuit modeling of the injection mechanism on the one hand, and on pulse design and equalization on the other hand. Two circuit models are developed. The former employs measurement/simulation data along with port-reduction techniques to model noise injection through near-field probes by means of internal induced sources. Conversely, the latter model only includes passive components and is derived starting from physical observation of the involved phenomena. Both models are compatible with circuit solvers and can be easily adapted for different traces under test. Since pulse-like noise is usually broadband, suitable stress waveforms are utilized to obtain different noise spectra. Also, in order to precisely control the shape of the waveform reaching the targeted pin, an equalization procedure is employed. These models and techniques can be easily applied to amplification systems originally designed for frequency-domain tests, thus providing a comprehensive solution for the design of broadband immunity tests in the time domain. The feasibility and accuracy of the proposed methodology are proved by full-wave simulations and measurements

Spatial resolution study for magnetic near-field probe

Spatial resolution is an important factor of near-field probe, which represents the ability to distinguish two close radiation sources. Traditional definition of spatial resolution is the distance between peak point and -6dB point when measuring microstrip line. The definition has disadvantage and limitation. In this topic, spatial resolution for magnetic near-field probe is studied, and three dimensions of spatial resolution are put forward. An optimized measurement setup is presented to reflect spatial resolution of probe properly. Then, an example is given to show how spatial resolution affects field distribution in near-field measurement --Abstract, page iv

Noncontact Wideband Current Probes with High Sensitivity and Spatial Resolution for Noise Location on PCB

This paper develops an improved noncontact current probe for locating the noise source to estimate the electromagnetic interference emission on printed circuit board (PCB). The miniature current probe is fabricated in a four-layer PCB with high-performance dielectric RO4003C. The designs of isolated via array and matching via-pad structures are used to optimize the performance of probe. The probe can then be used for wideband electromagnetic compatibility test from 9 kHz to 10 GHz under narrow and complex conditions. The current probe can be sensitive enough to detect the weak current signal as small as -130 dBA and has a spatial resolution of 1 mm. The application of current probe in noise location on PCBs based on measured surface scan method is investigated in this paper. And two near-field measurement results compared with the reference probe are used to illustrate the new features of the probe