[Gb-ccb] Filtering connectors on the PCB

[Martin Shepherd]

On Tue, 26 Aug 2003, John Ford wrote:
> Hi Martin.  Could you give us information on the cable and connectors
> you wanted to use before the RFI question arose?  I seem to remember
> it was a mass-terminated type twisted pair cable and associated
> connectors.  It's quite possible we have a source for such a beast in
> the RFI flavor..

I was tentatively looking at Amphenol SkewClear cable with 24-pair,
12X InifiniBand patch cables. Here are some links to pertinent
information:

Amphenol SkewClear cable:

 http://www.spectra-strip.amphenol.com/ecpdfs/New SKEWCLEAR Brochure 2-25-02.pdf

Amphenol Infiniband patch cables:

  http://www.amphenol-aipc.com/infinib.htm

More details about Infiniband connectors:

  http://www.fcal.fujitsu.com/pdf/FCN-260_MicroGiGaCN.pdf

Unfortunately I don't know how much crosstalk these connectors add.
The fact that the connectors place shielding ground planes between
neigboring pairs, implies that the crosstalk performance ought to be
excellent. However the only specification in the above link is that
for steps with 100 pico-second rise times, the near-end crosstalk is
4%. I assume that at much lower frequencies, this gets orders of
magnitude better, but I don't know if it reaches 0.05% (-65dB) at
10MHz, which is what I am looking for.

I can't find any Infiniband feedthrough bulkhead connectors, filtered
or otherwise, although I suppose that at a pinch, I could make my own
using a pair of PCB mounted sockets. Of course the receiver box would
need something similar.

Another concern is the need for some way to terminate or cap the
socket in the receiver box, when the CCB isn't connected to it. I
haven't found anything suitable for this.

By the way, when I wrote yesterday's email, I incorrectly thought that
twinax and triax were two names for the same thing.  I now realize
that this isn't the case, and that what I would need would be twinax
(ie. a twisted pair of two conductors, surrounded by a dielectric and
shield). Unfortunately, the connectors that I was refering to
yesterday are triax, and although Sabritec does sell small twinax
connectors, I don't see any bulkhead feedthrough connectors of this
type.

Martin