RF absorbing sheet materials? (5GHz)

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Discussion Overview

The discussion revolves around the use of RF absorbing sheets or tiles for attenuating RF radiation from PCB assemblies, specifically in the context of a 5GHz application. Participants explore various materials and their effectiveness in this application, including commercial products and alternatives.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the use of thin RF absorbing sheets for a 5GHz application and mentions their previous experience with such materials.
  • Another participant shares a link to a specific RF absorbing sheet product they are considering for testing.
  • Several participants suggest that black foam, commonly used for anti-static protection of ICs, could be effective for RF absorption, with one noting its use in waveguides as a dummy load.
  • There is a discussion about the tuning capabilities of RF absorbing sheets for specific frequencies, with one participant expressing interest in achieving low loss in the 2.4GHz-2.5GHz band while needing good loss around the 5GHz second harmonic band.
  • Another participant mentions the operational range of the black foam they use, indicating it operates between 850MHz to 1GHz.

Areas of Agreement / Disagreement

Participants generally agree on the potential effectiveness of black foam for RF absorption, but there is no consensus on the specific properties or effectiveness of the commercial RF absorbing sheets discussed. Multiple competing views on materials and their applications remain unresolved.

Contextual Notes

Participants express uncertainty regarding the specific tuning mechanisms of RF absorbing sheets and their effectiveness across different frequency ranges. There are also limitations in the information provided about the materials and their performance characteristics.

Who May Find This Useful

This discussion may be useful for engineers and researchers working with RF applications, particularly those involved in PCB design and RF radiation management.

berkeman
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Has anybody used thin RF absorbing sheets or tiles to attenuate RF radiation off of PCB assemblies? I've seen it used many years ago, and I have a 5GHz application that I'd like to try an absorbing sheet on. The PCBA is a few cm on a side, and the sheet or sheets would be applied directly on the side(s)...
 
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This is one of the sheets that I've requested samples of to try out...

http://www.wavexorb.com/products/product_details.php?PN=SN075-081&lang=en
 
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Also the sheets / pieces of black foam that is used for anti-static protection of IC's is brilliant for that use

I have even used wedge shaped sections in the end of waveguides on 5 and 10 GHz as a dummy load

Dave
 
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davenn said:
Also the sheets / pieces of black foam that is used for anti-static protection of IC's is brilliant for that use

I have even used wedge shaped sections in the end of waveguides on 5 and 10 GHz as a dummy load

Dave
Huh! I didn't think of that. I have anechoic chamber time scheduled for the end of this week, and will try anti-static foam as an option. That would be WAY cheaper than the commercial sheets. Thanks brother! :smile:
 
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no probs ... when I looked at that link you gave I wasn't really sure if it was for the same / similar sort of stuff or not ?
 
It looks like they can tune their sheets for particular frequencies. I'm not sure how they do it, but that's a nice feature. I want low loss in the 2.4GHz-2.5GHz band for 802.15.4 comm, but good loss around the 5GHz second harmonic band where we are having regulatory issues (for out-of-band harmonic energy).
 
I second the black foam, it's what our systems use, no idea what it is exactly, but I'll see what I can find out, I know they operate in the 850MHz to 1GHz range.
 

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