Hexagonally sectioned EMI shield
Article By : John Dunn
A hexagonally sectioned EMI shield structure can facilitate air flow as part of thermal management and even admit light under some circumstances.
An electromagnetic interference (EMI) shield structure that gets used by being embedded in sheet metal panels and walls is illustrated at the following URL:
https://esongemc.com/eng/bbs/content.php?co_id=Honeycomb_Vent_Regular_Type
Taking an excerpt from that web page and adding some illustrative sketching of our own, we come up with the following:
Figure 1 Hexagonally sectioned EMI shield structure.
Each hollow section of the grid of hexagonal tubes can be looked at as a single waveguide all by itself. As with any waveguide, there is a low frequency limit below which signals will not be carried down the waveguide’s length.
The low frequency limit is set by the waveguide’s geometry as that frequency whose half wavelength will just fit inside the metal structure. At any lower frequency, a signal’s half wavelength would exceed all of the waveguide’s physical dimensions and such a signal will not be propagated. It will be blocked.
Each hollow tube in the matrix of hollow tubes exhibits such waveguide properties. Taken en masse, the entire grid of hollow tubes will behave the same way. At 3/16th of an inch, the frequency limit is estimated as just under 32GHz. Compare this to the shielding specification for up to 18GHz.
A useful feature of this arrangement is that it facilitates air flow as part of thermal management and even the admission of light under some circumstances.
This article was originally published on EDN.
John Dunn is an electronics consultant, and a graduate of The Polytechnic Institute of Brooklyn (BSEE) and of New York University (MSEE).