[ibis-macro] Re: Clarifying why Deconvolution is required in a specific flow in BIRD 120
- From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
- To: "IBIS-ATM" <ibis-macro@xxxxxxxxxxxxx>
- Date: Mon, 29 Nov 2010 10:54:47 -0800
Sorry for the typo, the 2nd sentence was supposed to read:
... Walter is
correct in saying that IF the Rx_Init returns the filter's
impulse response, than de-convolution is not needed.
Arpad
===========================================================
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad
Sent: Monday, November 29, 2010 12:48 PM
To: Walter Katz; Morrison, Casey
Cc: IBIS-ATM
Subject: [ibis-macro] Re: Clarifying why Deconvolution is required in a
specific flow in BIRD 120
Walter, Casey,
I apologize for making an incorrect statement. Walter is
correct in saying that is the Rx_Init returns the filter's
impulse response, than de-convolution is not needed.
Arpad
===========================================================
From: Walter Katz [mailto:wkatz@xxxxxxxxxx]
Sent: Friday, November 19, 2010 6:31 PM
To: 'Morrison, Casey'; Muranyi, Arpad
Cc: IBIS-ATM
Subject: Clarifying why Deconvolution is required in a specific flow in
BIRD 120
Casey, Arpad,
De-convolution is required under BIRD 120 in only one specific case that
I will describe below:
The de-convolution case requires a channel with a Tx AMI model that has
Init_Returns_Impulse=True and GetWave_Exists=True. The Tx AMI_GetWave
function would include both the Tx equalization and affects such as
pattern dependent jitter.
The Rx AMI model has GetWave_Exists=False, and generates an output
impulse response which the IC vendor avers is sufficiently accurate to
represents the operation of the algorithmic part of the receiver. We
must assume that the Rx model will determine its equalization settings
based on the impulse response that is generated by Tx AMI_Init, as many
Rx AMI_Init models do today.
With this combination of Tx/Rx models, the EDA tool can run a
statistical analysis of the channel using Tx AMI_Init and Rx AMI_Init.
It is when users want the EDA tool to do a time domain simulation which
includes the pattern dependent jitter represented within the TX
AMI_GetWave function that de-convolution is required. If the output of
Rx AMI_Init was convolved with the output of Tx AMI_GetWave, the result
would double count the Tx Equalization since it is included in both the
Tx AMI_GetWave result, and the output of Rx AMI_Init (since it was
included in the input to Rx AMI_Init). One method to do a time domain
simulation that includes the accurate Tx AMI_GetWave functionality and
does not double count the Tx equalization is to determine the impulse
response of the Rx filter by using de-convolution between the input to
Rx AMI_Init and the output of Rx AMI_Init. EDA vendors have expressed,
and have written into BIRD 120 alternatives to doing de-convolution
which range from "Do not do time domain simulation - IT HURTS", to
relying that the tool can turn off optimization in Rx AMI_Init, and just
run a solution space to determine the optimum Rx tap settings, and then
call Rx AMI_Init with the optimal tap settings and an input that does
not include the Tx equalization.
Bottom line is either do not do time domain simulation, manually
optimize the Rx filter, or de-convolution.
There are alternatives, however. The model can implement the ability of
returning the impulse response of the filter alone, or the model
developer can implement an Rx AMI_GetWave, which would apply the Rx
filtering directly to the output fo Tx AMI_GetWave.
Walter
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