EMI Troubleshooting with the Latest-Generation Oscilloscopes
Tektronix
This application note from Tektronix provides practical techniques for diagnosing EMI compliance failures using modern oscilloscopes with time-correlated RF measurement capabilities. It explains how to interpret EMI test reports, noting that reported frequencies may not precisely match the actual source due to resolution bandwidth and detector type limitations. The paper covers near-field probing fundamentals, distinguishing between H-field probes (suited for low-impedance, high-current sources like power supplies and transmission lines) and E-field probes (suited for high-impedance, high-voltage sources like unterminated traces). A key capability highlighted is Spectrum View on the Tektronix 4, 5, and 6 Series MSOs, which enables simultaneous time-domain and frequency-domain analysis using digital down converters, eliminating the need to synchronize separate instruments. A case study demonstrates how a broadband EMI event around 140 MHz was traced to its source by correlating RF amplitude bursts with coincident circuit activity on the board.