Path: EDN Asia >> Design Centre >> Communications/Network >> Oscilloscope for EMI debugging? Really? (Part 1)
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Oscilloscope for EMI debugging? Really? (Part 1)

31 May 2013  | Alvin Ding, Markus Herdin

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Regular spectral features, like emissions from clock lines, are shown in a different colour than emissions that correspond to intermittent events like spikes from a switched-mode power supply. This is achieved without changing any parameter of the FFT.

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Figure 2: Overlap FFT processing splits the recorded signal into several parts before applying the FFT. This ensures for high sensitivity for spurious events and allows colour grading of spectral parts according to their frequency of occurrence.

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Figure 3: Emissions captured with a near-field probe close to the switched mode power supply (top: time signal, bottom: spectrum). The blue spectral lines correspond to the spikes in the time signal while the yellow spectral lines are regular spectral parts coming from clock lines.

Together with FFT gating, which allows limiting the spectral analysis to a user-defined temporal window, you can now easily find out which parts of the time-domain signal cause which features of the spectral display. This allows for correlation of unwanted emission with parts of the captured time signal, thus letting you get closer to the root-cause of the EMI problem.

Numerous features, like capturing intermittent emissions with mask test and stop-on-violation conditions, or the possibility of changing frequency domain settings after an acquisition has stopped, provide additional tools for debugging EMI problems. We will discuss these features and their use-cases in later parts in this series.

About the authors

Alvin Ding
Business Development
Rohde & Schwarz
Alvin Ding has years of experience in the test & measurement industry, with extensive knowledge and focus on the latest and emerging technologies, such as high-speed serial data and RF. Alvin received his bachelor's degree with honours in electrical and electronics engineering (EEE) from Nanyang Technological University, Singapore. Alvin received the EEE Excellence award for his outstanding contributions and excellence in academic performance throughout his study.
Dr. Markus Herdin
Senior Marketing Expert Oscilloscopes
Rohde & Schwarz
Markus Herdin has 12 years of experience in the electronics and mobile communications industry with assignments in research, product development, corporate strategy and marketing. He received his master's and PhD in electrical engineering with highest honours from the Vienna University of Technology and his MBA with honours from the University of Chicago Booth.

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