Author Topic: Vent holes and EMI  (Read 505 times)

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Offline Pack34

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Vent holes and EMI
« on: January 28, 2019, 02:09:54 pm »
I can't seem to remember the rule of thumb for the acceptable diameter for vent holes for immunity. I could have sworn it was something like the diameter of the vent has to be less than 1/2 of the maximum wavelength, but that seems large.
 

Offline OwO

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Re: Vent holes and EMI
« Reply #1 on: January 28, 2019, 03:40:28 pm »
Depends on how much isolation you need. I recall it's more like 1/20th of the wavelength for good isolation (>50dB). The amount and density of the holes are also important, as well as how close the holes are to your circuitry.
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Online coppercone2

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Re: Vent holes and EMI
« Reply #2 on: January 28, 2019, 05:02:00 pm »
There are example radiation graphs to give you an idea. Rf honeycomb is an option.
 

Offline Tomorokoshi

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Re: Vent holes and EMI
« Reply #3 on: January 28, 2019, 07:07:13 pm »
The other suggestions are correct. For more details, see "Noise Reduction Techniques in Electronic Systems" by Henry W. Ott.

Key takeaway: watch out for slot antennas. These are very easy to accidentally design in, particularly if penny-pinching mechanical engineers are involved.
 


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