FreeLists / si-list / [SI-LIST] Relativity in EMC design

[Zhangkun <zhang_kun@xxxxxxxxxx>]

Hi all
 
Currently, we have measured the radiation of signal line on external layer
of PCB. Based on the measurement result, we could gotten some
design-guideline for layout.
 
For example, there is a  external line of 6000mil. When the stimulus is 5mV
at 400MHz, the RE radiation at 3m is 40dbuV/m. The FCC RE limitation is
47dbuV/m. There is remaining margin of 7db.
 
My question is 7db is enough or not. On the PCB, there will be more than one
line, which carry signal of 400MHz. The RE radiation maybe reinforce. How to
evaluate the relativity effect of diffrent line carrying 400MHz signal?
 
Any advice will be helpful.
 
Best Regards
 
Zhangkun
2008.5.13

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