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EMI scans verify chip design and accelerate time-to-market

8/11/2011 05:36 PM EDT
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re: EMI scans verify chip design and accelerate time-to-market
EMSCAN   8/23/2011 8:07:35 PM
Thanks Zeeglen. It would be interesting to know exactly ... *** This is a really just matter of semantics. Fmod is the modulation frequency of the SSC profile and is the reciprocal of the clock period. Fmod or Tmod could be used to express the modulation signal. Usually the modulation signal is expressed in frequency. *** Fmod was 20kHz at +-1.5%.. This is a register setting in the Deserializer, if is done on-chip and is not precise. *** RBW for measurement was 1MHz. It would also be interesting to know... *** The scope of this testing was to compare the set up with Straight outputs vs. SSCG Outputs, in the set up, boards, settings selected, the data that was presented was observed. Additional testing could be done as a follow in to further isolate cause and effects. Where did that 820 MHz signal... *** This was a A vs B test in an open lab. Additional tests could be run to identify the source of the signal. The 824MHz could most likely be coming from the cell phone and tower frequencies nearby; since measurements were not done in an enclosed camber. In making various noise level and background this spike was intermittent and was seen there also. The scope of the data presented was the overall shape, and reduction when comparing the apple-to-apple emission profile. An ambient noise spectral scan should have been done before hand and automatically subtracted from the test spectral scan. Next time.

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re: EMI scans verify chip design and accelerate time-to-market
zeeglen   8/18/2011 8:29:11 PM
It would be interesting to know exactly what numerical value Tmod is (wrongly labeled Fmod in Fig 1) and what is the RBW of the spectrum analyzer used for the emissions plots of Figures 2 and 3. It would also be interesting to know what happened to all the harmonics between 300 and 600 MHz (and higher) in Fig 3; SSCG and narrow RBW at the SA cannot account for the 35 plus dB reduction. Where did that 820 MHz signal in Figure 3 come from? It was not present with SSCG turned off in Figure 2. SSCG will not protect adjacent wideband systems (intra-vehicle or the vehicle in the next lane) from radiated emissions. This appears to be a typical "wool over the eyes" marketing exercise. Either that, or measurement error - while the measurement tool has merit is it susceptible to fields from other devices used by other teams that share the same lab? (been there)

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re: EMI scans verify chip design and accelerate time-to-market
GREAT-Terry   8/18/2011 5:55:56 AM
Near Field EMI scan is a good idea. However, not many high speed devices provide such data for reference. Hope more IC vendors are aware of this need and make use of the scan data as a powerful marketing tool (at least it attracts the eyeballs of many engineers who have to deal with EMI sensitive applications)

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