Troubleshooting EMI in Embedded Designs
Rohde and Schwarz
This white paper from Rohde & Schwarz introduces EMI troubleshooting techniques for embedded designs using the R&S RTO series of digital oscilloscopes. As designs grow denser and integrate multiple technologies in small spaces, microcontroller-based systems face susceptibilities including unexpected state changes on input pins and corruption of clock signals — all potential sources of EMC compliance failures. The paper highlights two key EMI culprits: switching power supplies and power amplifiers. For power supplies, the RTO's correlated multiple gated FFT measurements allow engineers to view how the radiated RF spectrum changes at different time periods during switching events. For power amplifiers, monitoring ramp-up and ramp-down characteristics is critical, as abrupt power-down behavior can generate spurs and widen spectral emissions. The RTO's unique single-core A/D converter eliminates interleaving artifacts found in typical oscilloscopes, providing improved noise floor and dynamic range essential for near-field probing with E and H field sniffer probes.