[SI-LIST] Re: return loss of whole channel
- From: "Chen, Sherman" <sherman.chen@xxxxxxx>
- To: John Lin <johnlinc@xxxxxxxxx>
- Date: Mon, 22 Dec 2014 17:28:11 +0000
Resend for I was told the text was messed up.
Best Regards,
Sherman Chen
Signal Integrity
EMC Global Hardware Engineering
Tel: +86 21 60951100-3329
From: Chen, Sherman
Sent: Tuesday, December 23, 2014 1:06 AM
To: 'John Lin'
Cc: si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] return loss of whole channel
Hi John,
Thanks. Actually my question is a bit different. As you know in a spec. that
defines several reference points at both TX and RX sides, the RLs are all
defined as “looking into” the reference point rather than “look outward” to the
passive channel. Meanwhile there are RLs defined for parts of the channel such
as cable, connector but I haven’t see RL defined over the whole channel. I
think it would be useful to give such a spec. for it can facilitate the
validation of the channel.
I will go find IB spec. to see if it defines the channel RL.
Best Regards,
Sherman Chen
Signal Integrity
EMC Global Hardware Engineering
Tel: +86 21 60951100-3329
From: John Lin [mailto:johnlinc@xxxxxxxxx]
Sent: Tuesday, December 23, 2014 12:36 AM
To: Chen, Sherman
Cc: si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] return loss of whole channel
Hi Sherman,
Check Infiniband, I am sure there is spec for RL. I asked a similar
question previously in SI-List.
You can refer to the archive:
"http://comments.gmane.org/gmane.technology.electronics.signal-integrity/19301";.
Thanks
John Lin
SI/PI simulation design at Lenovo
2014-12-22 22:03 GMT+08:00 Chen, Sherman <sherman.chen@xxxxxxx>:
Dear si-listers,
Merry Christmas!
While many of you are inside the holiday aura I wish a little bit technical
discussion could also become a part of your enjoyment - that's what we
engineers like, right:)
We are currently investigating an issue which made us think of this question
"should there be a return loss spec defined for the whole channel"?
I searched some most popular specs and the table below is a summary of the RL,
IL values in those specs (Comments and corrections are very welcome).
I didn't find the requirement on the whole channel return loss in any of them.
As we know, given the worst case RL at each test point, and the min IL of each
segment, the whole channel RL can be readily calculated. Is the reason not
giving this parameter due to not all segments are well defined in whichever of
these standard, or there is other reasons preventing from doing so?
PCIe
SAS3
FC-PI-5
(1600-DF-EL-S)
SATA2
SATA3
Transmitter
4dB
7.9dB
6.4dB
6dB
14dB @300MHz
Receiver
5dB
7.9dB
12dB
8dB
18dB @300MHz
Calibration channel
18dB
Connector
20dB
Cable
7.9dB
Test load
15dB
Max Insertion loss of whole channel
20+-2dB
24dB
RL of whole channel
Notes:
1. All RL are min values of differential return loss.
2. The freq. point is the Nyquist freq. unless otherwise indicated.
Best Regards,
Sherman Chen
Signal Integrity
EMC Global Hardware Engineering
Tel: +86 21 60951100-3329
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