There are RJ45s with built in ferrite filters but that sounds like a poor band
aid. I also think you will find building wave guides a tad more difficult than
you anticipate. Fortunately I think there are several must better solutions.
Ethernet over fiber has been around for a long time. It may be hard to find
and may have interface problems. (i.e. both ends of the ethernet must be
modified to fiber. Sill a lot easy than building an EM wave guide.
Second, there are IR ethernet extenders. IR will bounce off a plaster wall so
I don't think it would be to hard to get it to propagate a short distance
through a plastic tubing helix screwed into your chamber wall. The helix will
effectively close RF aperture to prevent your noise transfer. I think you will
find it much easier to build optical wave guide rather than EM wave guide.
Fred Townsend
DC to Light
McInturff Gary wrote:
Dumb question maybe
I have to get a UTP Ethernet connection out of a semi-anechoic
chamber. There no anti-chamber so any unfiltered cable routing opening is a
major leak because of the opening and the induced noise on the cable itself.
Since Ethernet signals don’t like to be filtered. I’m considering two
options – neither of them make me real happy.
1) Find, if one exists, some sort of metallic RJ-45 bulkhead transition
connectors and mount that into the transition panel. I’ve seen the plastic
versions for inter-connecting Ethernet cables, but the were neither metallic
nor bulkhead mounted.
2) Make an air dielectric waveguide out of foot or so ½ inch metal pipe and
attach that to the transition panel and route the cable through the “wave
guide” The opening itself even at ½ is larger than 18 GHz upper test
frequency, but the width of the wave guide buys me some attenuation – and I
don’t expect to see much in the way of ambient up that high anyway.
I don’t have an option of putting the test gear into the chamber with the
EUT. The test gear would be a worse problem.
I don’t think this is completely brain dead but don’t see any easier
solution, but this doesn’t address any induced ambient noise on the cable.
Your thoughts?
Thanks
Gary
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