Skin Depth Q: Cellphone Rings in Cavity

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    Depth Skin Skin depth
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Discussion Overview

The discussion revolves around the phenomenon of skin depth and its implications for electromagnetic interference (EMI) in a metal cavity created by enclosing a cellphone in two half-spheres of aluminum. Participants explore why the cellphone was able to receive a signal despite expectations based on the skin effect.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that a cellphone rang inside a metal cavity, questioning why this occurred despite the skin effect, which suggests that electromagnetic waves should not penetrate the metal.
  • Another participant suggests that RF signals can pass through very small gaps, implying that the enclosure may not have been completely sealed.
  • A third participant emphasizes that for effective EMI/EMC design, simply having aluminum touching aluminum may not suffice, and that additional measures such as contact fingers or mechanical pressure are necessary to ensure proper sealing.
  • A later reply acknowledges the advice and expresses intent to improve the sealing in future attempts.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the reasons behind the cellphone receiving a signal. There are multiple competing views regarding the effectiveness of the enclosure and the impact of small gaps.

Contextual Notes

Limitations include potential assumptions about the completeness of the seal and the specific conditions under which the skin effect operates. The discussion does not resolve the technical details of the skin effect or the specific design requirements for effective EMI shielding.

Who May Find This Useful

This discussion may be of interest to those involved in electromagnetic compatibility (EMC) design, radio frequency (RF) engineering, and anyone exploring the practical implications of the skin effect in metal enclosures.

Thierry12
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I placed a cellphone in 2 half-spheres that i closed afterwards to create a metal cavity (aliminium 1mm) and called it (with another cellphone). The phone rang even if it wasn't supposed to considering the skin effect (wavelength were about 0,04m and i couldn't see any holes). Anyone has a clue why?
 
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RF can get through very small gaps.
When you said you 'closed them' unless you made an airtight seal (difficult without some fancy machining) you didn't really close them.
Cell phones are designed to pick up very-very weak signals.
 
When you're designing enclosures for EMI/EMC, particularly at those frequencies, aluminum touching aluminum doesn't count. You have to use things like contact fingers, solder, mechanical pressure, conducting gels, and so on.
This link will give you some considerations and examples
http://www.cotsjournalonline.com/home/article.php?id=100057
 
Last edited by a moderator:
Next time i will close them proplerly! ty
 

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