[SI-LIST] Re: Estimate ISI with S parameters -- Using TDR to do SDD21 correlation?
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: "John Lin (ææç)" <John@xxxxxxxxxxxx>
- Date: Tue, 17 May 2005 00:18:32 -0400
John
In theory, S11 contains all the information that you need to
characterize a channel, as does a TDR waveform. In practice, S11 is an
extremely sensitive to all discontinuities and losses in the channel.
Since it is a round trip measurement, every feature in the channel has
twice the impact on the returned waveform. If the reflected waveform
that you measure has a reasonable match to your simulated waveform, then
you're in the right "ballpark." But there's nothing like a good TDT or
insertion loss measurment to know exactly how well the system will perform.
regards,
Scott
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed is the registered service mark of
Teraspeed Consulting Group LLC
John Lin (ææç) wrote:
>Scott,
>
>Thanks again.
>
>What you mean is that if simulation for SDD11 matchs TDR measurement, then it
>implies simulation SDD21 shall be correct ?
>Are there any factors to make the answer "NO"?
>
>Thanks,
>John
>
>-----Original Message-----
>From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx]
>Sent: Tuesday, May 17, 2005 11:54 AM
>To: John Lin (ææç)
>Cc: steve weir; si-list@xxxxxxxxxxxxx
>Subject: Re: [SI-LIST] Estimate ISI with S parameters -- Using TDR to do SDD21
>correlation?
>
>John,
>
>With some of the more recent versions of HSPICE there is a built in PRBS pulse
>source. You can use this to excite the s-parameter model and look at the ISI
>with an eye display. I think this is the easiest way to get a feel for ISI.
>You can certainly also create an impulse pulse and look at the channel
>response. There's no reason why you can't also do this in HSPICE.
>
>As for correlation with only a TDR, this will work well if you set up the
>identical simulation with the simulator. You can capture the TDR pulse from
>your instrument and create a PWL source with it. Then drive your simulation
>with the TDR to see how good the model/measured match is.
>
>Regards,
>
>scott
>
>Scott McMorrow
>Teraspeed Consulting Group LLC
>121 North River Drive
>Narragansett, RI 02882
>(401) 284-1827 Business
>(401) 284-1840 Fax
>
>http://www.teraspeed.com
>
>Teraspeed is the registered service mark of Teraspeed Consulting Group LLC
>
>
>
>John Lin (ææç) wrote:
>
>
>
>>Hi Scott,
>>
>>Thank you for helps.
>>Yes, I can run circuit with s-parameter model. Here, one question. Before,
>>I would like to run random pattern for ISI. Recently studying, show only
>>need to do pulse response to see
>>how the result waveform penetrates to next signal. It makes sense to me and
>>also easier to run simulation. Any comments on this method?
>>
>>Also, I don't have a 4 port VNA to measurement SDD21 for correlation. However
>>I have a TDR with only one differential module to measure trace impedance
>>(SDD11).
>>(I cannot use TDT functions since only one module installed)
>>
>>Is it reasonable to correlate SDD11 as a indicator for the correlation of
>>SDD21? Do I miss something?
>>
>>Thanks,
>>John
>>
>>
>>________________________________
>>
>>From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx]
>>Sent: Monday, May 16, 2005 9:21 PM
>>To: John Lin (ÂLÂÃÂÃ)
>>Cc: steve weir; si-list@xxxxxxxxxxxxx
>>Subject: Re: [SI-LIST] Re: Estimate ISI with S parameters?
>>
>>
>>John
>>
>>If you have HSPICE available, you can set up a circuit with s-parameter
>>modeling to measure any pattern dependent ISI that you want.
>>
>>scott
>>
>>
>>Scott McMorrow
>>Teraspeed Consulting Group LLC
>>121 North River Drive
>>Narragansett, RI 02882
>>(401) 284-1827 Business
>>(401) 284-1840 Fax
>>
>>http://www.teraspeed.com
>>
>>Teraspeed(r) is the registered service mark of Teraspeed Consulting
>>Group LLC
>>
>>
>>John Lin (ÂLÂÃÂÃ) wrote:
>>
>> Hi Steve,
>>
>> Thanks for your helps.
>>
>> >From other response, it looks like, I need to transfer channel's S =
>> parameters into time domain
>> and do pulse repsonse to see how the curve at the falling edge =
>> penetrates to the period=20
>> Of a next signal.
>>
>> In your mail, ISI is relative to attenuation,SDD21.
>>
>> I read SAS/SATA spec. There is a ISI compliant curve shown on a SDD21 =
>> chart.=20
>> The ISI curve is steeper than SDD21 compliant curve.=20
>>
>> How to generate a ISI curve at the frequency domain by simulation to =
>> check if meet the requirement.?
>>
>> Thanks,
>> John
>>
>>
>>
>>
>> -----Original Message-----
>> From: steve weir [mailto:weirsi@xxxxxxxxxx]=20
>> Sent: Saturday, May 14, 2005 1:34 AM
>> To: John Lin (=AAL=B4=C2=B7=D7); si-list@xxxxxxxxxxxxx
>> Cc: John Lin (=AAL=B4=C2=B7=D7)
>> Subject: Re: [SI-LIST] Estimate ISI with S parameters?
>>
>> John variable attenuation versus frequency within the symbol frequency =
>> band will give rise to ISI as the amplitude at any given point will =
>> depend on the previous history of symbols, and hence the name ISI.
>>
>> Steve
>> At 10:25 AM 5/13/2005 +0800, =3D?big5?B?Sm9obiBMaW4gKKpMtMK31yk=3D?=3D =
>> wrote:
>>
>>
>> Dear all SI experts,
>>
>> Can some ones explain how to relate ISI (inter-symbol
>> interference) to=20
>> S parameters?
>>
>> What can be observed from S -parameter for differential 4
>> parts=20
>> simulation? For example, crosstalk, attenuation,
>> reflection,....etc.
>>
>> Thanks,
>> John
>>
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