[SI-LIST] Re: relationship between reeceiver jitter transfer and jitter tolerance
- From: "Cheng, Chris" <chris.cheng@xxxxxx>
- To: Vinu Arumugham <vinu@xxxxxxxxx>
- Date: Mon, 30 Jul 2012 23:00:18 +0000
I believe jitter transfer in this case means the amount of jitter pass through
the receiver structure - the CDR tracked jitter.
In order to compensate for the channel loss, the receiver equalizer will
amplifier high frequency components independent of the actual signal or high
speed jitter.
At low frequency, there is no gain in the equalizer and the CDR track the input
jitter, the net jitter at sampling point is zero.
Chris Cheng
Distinguished Technologist , Electrical
Hewlett-Packard Company
+1 510 413 5977 / Tel
chris.cheng@xxxxxx / Email
4209 Technology Dr
Fremont, CA 94538
USA
-----Original Message-----
From: Vinu Arumugham [mailto:vinu@xxxxxxxxx]
Sent: Monday, July 30, 2012 3:01 PM
To: Cheng, Chris
Cc: si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: relationship between reeceiver jitter transfer and
jitter tolerance
I assumed the following definition:
Jitter transfer = recovered clock jitter/input jitter.
Since the CDR cannot track high frequency jitter (regardless of
magnitude), the recovered clock will have zero jitter. Non-equalizable
high frequency jitter magnitude is limited to UI - RX impairments.
Thanks,
Vinu
On 07/30/2012 02:21 PM, Cheng, Chris wrote:
>> For jitter frequencies above the corner frequency, jitter transfer is 0. For
>> jitter frequencies below the corner frequency, jitter transfer
>> asymptotically approaches 1
> Are you confusing reference clock jitter tolerance with input jitter
> tolerance ? If the above statement is true, I can have my input jitter to
> infinity above "corner frequency" and the transfer will still be zero so my
> wonder receiver can tolerance jitter of any amplitude above the corner
> frequency. How does the actual signals get through then ? :-)
>
> Chris Cheng
> Distinguished Technologist , Electrical Hewlett-Packard Company
>
> +1 510 413 5977 / Tel
> chris.cheng@xxxxxx / Email
> 4209 Technology Dr
> Fremont, CA 94538
> USA
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of Vinu Arumugham
> Sent: Monday, July 30, 2012 12:22 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: relationship between reeceiver jitter transfer and
> jitter tolerance
>
> Chris,
>
> "What if I modify slightly the definition of jitter tolerance to the receiver
> as, how much jitter can be applied to the input (instead of reference clock)
> before you have a receiver error."
> Specifications such as XAUI,XFI,SFI,XLAUI,CEI use this modified definition.
> Most of them do not specify reference clock jitter.
>
> Instead of using the UI as the break point perhaps the corner frequency of
> the tolerance vs. frequency curve should be used (usually Fbaud/1667). For
> jitter frequencies above the corner frequency, jitter transfer is 0. For
> jitter frequencies below the corner frequency, jitter transfer asymptotically
> approaches 1.
>
> Thanks,
> Vinu
>
> On 07/27/2012 07:07 PM, Cheng, Chris wrote:
>> Hi there,
>>
>> I think the classical definition of jitter transfer is related to how much
>> jitter at the input of receiver get transfered to the output of the receiver.
>> The classical definition of jitter tolerance is related to how much input
>> reference clock jitter is acceptable for a given bit error rate.
>> What if I modify slightly the definition of jitter tolerance to the receiver
>> as, how much jitter can be applied to the input (instead of reference clock)
>> before you have a receiver error.
>> A practical way of doing the above is to send a known pattern such as CJTPAT
>> to a receiver and then modulate it with a fixed frequency jitter. The
>> minimum jitter amplitude that will trigger errors will be defined as jitter
>> tolerance as above.
>> So my question is, if one does the experiment above and plot out the jitter
>> tolerance vs. frequency. How does that receiver jitter tolerance related to
>> the receiver transfer curve ?
>> Can I interpret the receiver jitter tolerance and transfer relationship as:
>> a) For jitter tolerance > UI, the jitter transfer is 1 or unity
>> b) For jitter tolerance < UI, the jitter transfer = UI - jitter tolerance -
>> "some constant"
>> where "some constant" is probably related to the setup and hold
>> requirements of the receiver
>>
>> Thanks in advanced,
>>
>> Chris Cheng
>> Distinguished Technologist , Electrical Hewlett-Packard Company
>>
>> +1 510 413 5977 / Tel
>> chris.cheng@xxxxxx / Email
>> 4209 Technology Dr
>> Fremont, CA 94538
>> USA
>>
>>
>>
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