SSC creates a series of narrow band harmonics that are separated by less
that the receiver bandwidth. This makes the signal look like a broadband
on a spectrum analyzer. For a good explanation of what is going on see the
following link.
http://www.interferencetechnology.com/spread-spectrum-clock-generation-theory-and-debate/
A review of a number of HDMI cables show that most have very long pig tails
connecting the shield of the cable to the connectors. This is poor
construction. If a cable has the shield enclosed around from cable to
connector then many HDMI problems are solved. This costs a few pennies
more but unfortunately few cables are constructed correctly. The link
below has a HDMI connector shell that should work great.
http://www.comoss.com/products/HDMI-Connector.php
Buy any cable and cut the end open and if you see a wire from the cable
shield to the connector shell and all the other wires are visible then this
cable will radiated much more than one with an enclosed end.
Good luck,
On Thu, Apr 9, 2015 at 11:48 AM, Ravinder Ajmani <ravinder.ajmani@xxxxxxxx>
wrote:
It is true that SSC is a way to fool the EMI Receiver. However the data
rates keep on increasing, and companies want to make cheap enclosures.
This does not leave many options to make the equipment meet the compliance
without the use of SSC. The improvement with SSC is not trivial. In case
of SAS3 (12 Gbps) which uses 1000 ppm SSC, the improvement can be over 10
dB.
Regards
Ravinder Ajmani
HGST, a Western Digital company
5601 Great Oaks Pkwy
San Jose, CA 95119-1003
ravinder.ajmani@xxxxxxxx
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Traa, Boris
Sent: Thursday, April 09, 2015 2:30 AM
To: jingboli@xxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: HDMI or DP EMI issue
SSC is a method to fool the EMI measurement equipment. B.t.w. for quasi
peak measurement (below 1 GHz) linear SSC will only help you for a few dB.
Regards
Boris
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Jingbo
Sent: donderdag 9 april 2015 2:11
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: HDMI or DP EMI issue
EMI has been a known issue for HDMI, which contains a forward clock and
does NOT allow SSC. The situation for DP should be much better due to
embedded clock and SSC (0.5% max).
Regards,
Jingbo
From: roglesbee@xxxxxxxxxxxxxxxxxxthat.
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: HDMI or DP EMI issue
Date: Wed, 8 Apr 2015 12:49:31 -0400
Frank,
0.5% is pretty much industry standard. You can go larger to get more
margin to radiated emissions limits, but you must make sure everything
downstream can track it. If HDMI specs 0.5% max, you should stick to
law.
Regards,
Rob Oglesbee
Radian Research
(765) 449-5505
This message, and any attachments to it, may contain information that
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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of jaehun jun
(Redacted sender "ranier9999@xxxxxxxxx" for DMARC)
Sent: Tuesday, April 07, 2015 7:47 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] HDMI or DP EMI issue
Dear all,I am studying HDMI or DP EMI issue.
One curiosity is Spread spectrum specifications of HDMI or DP is just
0.5%(5000ppm) with 33k modulation.I think Spread ratio seems to be too
low.I heard HDMI or DP cable is very expensive to meet EMI
specification(because it is shield cable).
Is it enoughà spread ratio(0.5%) to achieve commercial
specifications?or Doesn't Spread spectrumà work properly with high
spread spectrum ratio(high modulation rate)Ã ?
If you have any experienced about that. Please guide me.
Thank you.Frank.
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