LTSpice RLGC model from TNT field solver w-element model

Hi
First of all, condolences to everyone who knew Steve Weir. I referenced his
work in my masters thesis in physics a few years ago.
I'm trying to understand simulation of crosstalk by doing some field
solving of a trace pair using MMTL (the Multilayer Multiconductor
Transmission Line 2-D and 2.5-D electromagnetic modelling tool suite,
http://mmtl.sourceforge.net/). The solver can output an HSpice w-element
model of the signal pair, and I'm trying to replicate the crosstalk levels
reported by the solver by setting up an equivalent circuit in LTSpice.
However, I am not quite sure how to translate all the details into an
equivalent circuit, so if I walk through my thought process doing this,
maybe someone can point if I'm doing anything wrong?
In the end of this email, I'm pasting the solver output from TNT 1.2.2, as
well as the w-element output.
The Spice model is a simple RLGC-model. One for the aggressor (I'll call
the components Ra, Ca and so on)and one for the victim (Rv, Cv ..), with an
extra capacitor for coupling between the two circuits (Cav). The inductors
are coupled using a coupling factor. A link to the LTSpice design is here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.asc
Following Eric Bogatins chapter on crosstalk in "Signal and Power Integrity
Simplified, 2nd ed", I came up with the values like this: From the
w-element file,

La = L0(1,1) = 3.29962e-007 H
Lv = L0(2,2) = 3.29953e-007 H
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.175

Ca = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cv = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cav = -1*C0(2,1) = 1.49773e-011 F

Ra = R0(1,1) = 11.4286 Ohm
Rv = R0(2,2) = 11.4286 Ohm

G0 and Gd is zero, and I omitted Rs , since I'm not really interested in
losses right now.

TNT calculates fare end crosstalk to and near end crosstalk to . I'm not
sure how to translate this to measurements in LTSpice, but I injected a 1V,
100ns, step into the aggressors resistor and measured how much signal was
crosstalked over at the Cav end of the victim circuit (a bit difficult to
explain without schematic, but here's a screen capture from LTSpice:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.png) The
crosstalked signal has an amplitude of about 18mV, which is about -55dB. I
interpret this as being near end crosstalk, since there is no actual length
in the model. The field solver reports near end crosstalk to be -41dB, but
far end crosstalk to be -57dB.

Am I doing anything right here?


Thanks in advance from
Johan



As reference, the field solver files are here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.xsctn
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.result
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.hspice-w.rlgc




2015 08 28 09:12:31 johan.lans NMMTL_2DLF

File = C:/Program Files (x86)/tnt-1.2.2/examples/xtalk
Number of Signal Lines = 2
Number of Ground Planes = 1
Number of Ground Wires = 0
Coupling Length = 1.00000 meters
Rise Time = 100000.0012 picoseconds
Contour (conductor) segments [cseg] = 10
Ground Plane/Dielectric segments [dseg] = 10
Conductivity RectCond1R1 = 5e+007 siemens/meter
Conductivity RectCond1R0 = 5e+007 siemens/meter
Note: minimum frequency for surface current assumptions is 1655 MHz.
Mutual and Self Electrostatic Induction:
B(Active Signal , Passive Signal) Farads/Meter
B( ::RectCond1R1 , ::RectCond1R1 )= 1.1691868e-010
B( ::RectCond1R1 , ::RectCond1R0 )= -1.6413763e-011
B( ::RectCond1R0 , ::RectCond1R1 )= -1.4977254e-011
B( ::RectCond1R0 , ::RectCond1R0 )= 1.1813248e-010

Mutual and Self Inductance:
L(Active Signal , Passive Signal) Henrys/Meter
L( ::RectCond1R1 , ::RectCond1R1 )= 3.2996223e-007
L( ::RectCond1R1 , ::RectCond1R0 )= 5.7727959e-008
L( ::RectCond1R0 , ::RectCond1R1 )= 5.7747599e-008
L( ::RectCond1R0 , ::RectCond1R0 )= 3.2995263e-007

Asymmetry Ratios:

Asymmetry ratio for inductance matrix:
0.034021% (max), 0.034021% (average)

**********
Asymmetry ratio for electrostatic induction matrix:
8.751856% (max), 8.751856% (average).
(Note values greater than 1% are a probable indication of too few
elements.
Try adjusting CSEG and DSEG attributes.)
**********

Characteristic Impedance (Ohms):
For Signal Line ::RectCond1R1= 53.1239
For Signal Line ::RectCond1R0= 52.8495

Characteristic Impedance Odd/Even (Ohms):
odd= 45.186
even= 62.1082

Effective Dielectric Constant:
For Signal Line ::RectCond1R1= 3.36577
For Signal Line ::RectCond1R0= 3.40061

Propagation Velocity (meters/second):
For Signal Line ::RectCond1R1= 1.6340992e+008
For Signal Line ::RectCond1R0= 1.6257061e+008

Propagation Velocity Odd/Even (meters/second):
odd= 1.65982e+008
even= 1.60201e+008

Propagation Delay (seconds/meter):
For Signal Line ::RectCond1R1= 6.1195795e-009
For Signal Line ::RectCond1R0= 6.1511734e-009

Propagation Delay Odd/Even (seconds/meter):
odd= 6.02475e-009
even= 6.24218e-009

Rdc:
Rdc(Active Signal , Passive Signal) Ohms/Meter
Rdc( ::RectCond1R1 , ::RectCond1R1 )= 1.1428571e+001
Rdc( ::RectCond1R1 , ::RectCond1R0 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R1 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R0 )= 1.1428571e+001

Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )= -1.48130e-003 = -56.58711 dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )= 9.25449e-003 = -40.67295 dB

NOTE: Cross talk results assume there are no reflections.









*
johan.lans 5 years 21 days

9 answers


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Answered byjohan.lans 5 years 12 days
Hi
Thanks to help from all of you, I now get some pretty decent numbers from
my spice simulation regarding next. Fext is still an order of magnitude
higher in spice. Tnt and si9000 also agrees pretty well.
I'm pretty happy with what I've learned so far, and if I think about the
Fext case a bit more I'll probably figure it out.
Best regards
Johan
Den 4 sep 2015 17:33 skrev "Michael Degerstrom" :

Hi Johan,

Always reset the default CSEG and DSEG from 10 to a much larger value,
say 100. This may fix your asymmetry errors. The default settings were
probably set 25 years ago when computers were much slower.

I remember finding some inconsistencies in the TNT output about 20 years
ago but I don't remember the details. I did work with one of the
developers at that time to get results that seemed to makes sense.

You are doing the right things by correlating simulator output to theory.
If you want to extend your correlation efforts you'd have to build coupled
L/C "ladder" networks and make sure your L/C elements have delay
(=sqrt(L/C)) about 1/10 of your rise time. LTSpice may or may not have a
w-element model but you can learn a lot more building these ladder
networks. For example, you'd build a subckt of one and chain them together
in the main netlist. I may have some old PERL scripts that extract TNT
results and build up spice netlists.

Then you'd have to extend on Istvan's suggestions on termination to
provide near and far end termination networks to terminate all modes.
There is some literature out there on equations for crosstalk with
different termination conditions but I think I've found problems with the
FEXT cases.

Regards

Mike Degerstrom


On Sep 2, 2015, at 2:45 AM, Johan Lans wrote:

Hi
Sorry, I should have mentioned that I scaled down the coupling length to
1mm, just to get a more realistic lumped element. Also, I discovered that
TNT was unhappy about the capacitance matrix not being symmetric, so i
added a 75um dielectric layer above the traces, which fixed the problem.
This means somewhat adjusted values:
These are per meter values:
La = L0(1,1) = 3.3022920e-007 H/m
Lv = L0(2,2) = 3.3022920e-007 H/m
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.176

Ca = C0(2,1) + C0(1,1) = 1.12412737e-10 F/m
Cv = C0(2,1) + C0(1,1) = 1.12412737e-10 F/m
Cav = -1*C0(2,1) = 2.5099933e-011 F

Ra = R0(1,1) = 11.4286 Ohm/m
Rv = R0(2,2) = 11.4286 Ohm/m



I didn't know about crosstalk coefficients. Are you using the definitions
on this page for the calculations:
http://www.polarinstruments.com/support/si/AP8164.html ?? Anyway, the
coefficients are obviously normalized to length, so my rescaling
shouldn't
matter.

Using the updated values above I get (using definition from polar page):
Kb = 0.25*(2.5099933e-011/1.12412737e-10 + 0.176) = 0.10
Kf = (Cm/C-Lm/L) = 2.5099933e-011/1.12412737e-10 - 0.176 = 0.047


Is this in line with your calculations?

Also, I played around with an evaluation of Polar SI9000. With the same
stackup I get a very similiar RGLC-matrices, but it also reports this:


Kb(NEXT) Kf FEXT
8,938337E-02 1,962233E-11 1,962233E-04

At least Kb seems to match...

TNT reports this:
Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )= 2.30877e-007 = -132.73240 dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )= 1.18904e-005 = -98.49607 dB



Here is a link to my LTSpice model:

https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk2.asc


Many thanks for the help

/Johan




2015-09-02 4:07 GMT+02:00 Istvan Novak :

Hi Johan,

Are you still using the L and C matrix values from your first posting?
With those numbers you can calculate the Kb backward crosstalk
coefficient
and Kf forward crosstalk coefficient and they come out 0.0625 and 0.025,
respectively. LTSPICE is pretty accurate if the input models are
correct.
E-mail me offline the LTSPICE deck.

Regards,
Istvan







On 9/1/2015 9:14 AM, Johan Lans wrote:

Hi
Well, yes and no. I have simulated propagation delay on the
transmission
line (one lump LGCR) in LTSpice with parameters from TNT, and they are
spot
on the same as TNT reports them. This makes me think that the Spice
model
is good. However, TNT reports NEXT and FEXT values to be quite
different
than what I'm getting from LTSpice. TNT FEXT -92.7dB=, TNT NEXT
=-58.5dB,
LTSpice FEXT = -273dB, LTSpice NEXT = -226dB.
A problem is now that I don't know how TNT calculates crosstalk
levels. In
LTSpice I'm also getting quite a lot of overshoot and ringing in the
victim, which might indicate a problem with accuracy in LTSice (?).
My next step is to get an evaluation copy of Si9000, from Polar. I read
that it too exports LGCR-parameters, so I can then expirement with
those
parameters aswell. I'm thinking that the Polar tool is well trusted and
can
be used as a reference to both LTSpice and TNT.
Best Regards, Johan

2015-09-01 14:38 GMT+02:00 Istvan Novak :

Hi Johan,

I am glad you found it useful.
Does it work now? Do you get the expected answer?

Regards,
Istvan





On 9/1/2015 8:24 AM, Johan Lans wrote:

Great answer, thank you very much.
Johan
Den 31 aug 2015 04:47 skrev "Istvan Novak" :

Johan,

There are a few things that you will need to change to make this
work.
To get near end and far end crosstalk, you need four ports that you
may
want to terminate in its average characteristic impedance: the
geometric
mean of even and odd mode impedances). Though you may not be
interested
in
delay and length, the way how the numbers are supplied, refer to a
particular length, so your circuit will be a four port circuit. You
need
to check the field solver, what unit length it assumes. From the L
and C
numbers you quote, it may be one meter. The characteristic
impedance
from
these L and C numbers appears to be close to 50 ohms, so the Ra and
Rv
numbers may represent the losses. If you want a lossless equivalent
circuit, you can replace those numbers with zero, but you have to
add
the
proper termination at all four ports. Finally, this is a
single-lump
equivalent circuit, because you have one lumped capacitance and one
lumped
inductance for the entire length. As a minimum, you may want to
split
the
capacitance values into two (half values) and place them at the
input
and
output instead of just being at the output. if you really want a
wideband
model, you will need more lumps.

Hope this will get you going.

Regards,

Istvan Novak
Oracle



On 8/28/2015 3:36 AM, Johan Lans wrote:

Hi

First of all, condolences to everyone who knew Steve Weir. I
referenced
his
work in my masters thesis in physics a few years ago.
I'm trying to understand simulation of crosstalk by doing some
field
solving of a trace pair using MMTL (the Multilayer Multiconductor
Transmission Line 2-D and 2.5-D electromagnetic modelling tool
suite,
http://mmtl.sourceforge.net/). The solver can output an HSpice
w-element
model of the signal pair, and I'm trying to replicate the crosstalk
levels
reported by the solver by setting up an equivalent circuit in
LTSpice.
However, I am not quite sure how to translate all the details into
an
equivalent circuit, so if I walk through my thought process doing
this,
maybe someone can point if I'm doing anything wrong?
In the end of this email, I'm pasting the solver output from TNT
1.2.2,
as
well as the w-element output.
The Spice model is a simple RLGC-model. One for the aggressor (I'll
call
the components Ra, Ca and so on)and one for the victim (Rv, Cv ..),
with
an
extra capacitor for coupling between the two circuits (Cav). The
inductors
are coupled using a coupling factor. A link to the LTSpice design
is
here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.asc
Following Eric Bogatins chapter on crosstalk in "Signal and Power
Integrity
Simplified, 2nd ed", I came up with the values like this: From the
w-element file,

La = L0(1,1) = 3.29962e-007 H
Lv = L0(2,2) = 3.29953e-007 H
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.175

Ca = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cv = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cav = -1*C0(2,1) = 1.49773e-011 F

Ra = R0(1,1) = 11.4286 Ohm
Rv = R0(2,2) = 11.4286 Ohm

G0 and Gd is zero, and I omitted Rs , since I'm not really
interested
in
losses right now.

TNT calculates fare end crosstalk to and near end crosstalk to .
I'm
not
sure how to translate this to measurements in LTSpice, but I
injected
a
1V,
100ns, step into the aggressors resistor and measured how much
signal
was
crosstalked over at the Cav end of the victim circuit (a bit
difficult
to
explain without schematic, but here's a screen capture from
LTSpice:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.png) The
crosstalked signal has an amplitude of about 18mV, which is about
-55dB. I
interpret this as being near end crosstalk, since there is no
actual
length
in the model. The field solver reports near end crosstalk to be
-41dB,
but
far end crosstalk to be -57dB.

Am I doing anything right here?


Thanks in advance from
Johan



As reference, the field solver files are here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.xsctn
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.result

https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.hspice-w.rlgc




2015 08 28 09:12:31 johan.lans NMMTL_2DLF

File = C:/Program Files (x86)/tnt-1.2.2/examples/xtalk
Number of Signal Lines = 2
Number of Ground Planes = 1
Number of Ground Wires = 0
Coupling Length = 1.00000 meters
Rise Time = 100000.0012 picoseconds
Contour (conductor) segments [cseg] = 10
Ground Plane/Dielectric segments [dseg] = 10
Conductivity RectCond1R1 = 5e+007 siemens/meter
Conductivity RectCond1R0 = 5e+007 siemens/meter
Note: minimum frequency for surface current assumptions is 1655
MHz.
Mutual and Self Electrostatic Induction:
B(Active Signal , Passive Signal) Farads/Meter
B( ::RectCond1R1 , ::RectCond1R1 )= 1.1691868e-010
B( ::RectCond1R1 , ::RectCond1R0 )= -1.6413763e-011
B( ::RectCond1R0 , ::RectCond1R1 )= -1.4977254e-011
B( ::RectCond1R0 , ::RectCond1R0 )= 1.1813248e-010

Mutual and Self Inductance:
L(Active Signal , Passive Signal) Henrys/Meter
L( ::RectCond1R1 , ::RectCond1R1 )= 3.2996223e-007
L( ::RectCond1R1 , ::RectCond1R0 )= 5.7727959e-008
L( ::RectCond1R0 , ::RectCond1R1 )= 5.7747599e-008
L( ::RectCond1R0 , ::RectCond1R0 )= 3.2995263e-007

Asymmetry Ratios:

Asymmetry ratio for inductance matrix:
0.034021% (max), 0.034021% (average)

**********
Asymmetry ratio for electrostatic induction matrix:
8.751856% (max), 8.751856% (average).
(Note values greater than 1% are a probable indication of too
few
elements.
Try adjusting CSEG and DSEG attributes.)
**********

Characteristic Impedance (Ohms):
For Signal Line ::RectCond1R1= 53.1239
For Signal Line ::RectCond1R0= 52.8495

Characteristic Impedance Odd/Even (Ohms):
odd= 45.186
even= 62.1082

Effective Dielectric Constant:
For Signal Line ::RectCond1R1= 3.36577
For Signal Line ::RectCond1R0= 3.40061

Propagation Velocity (meters/second):
For Signal Line ::RectCond1R1= 1.6340992e+008
For Signal Line ::RectCond1R0= 1.6257061e+008

Propagation Velocity Odd/Even (meters/second):
odd= 1.65982e+008
even= 1.60201e+008

Propagation Delay (seconds/meter):
For Signal Line ::RectCond1R1= 6.1195795e-009
For Signal Line ::RectCond1R0= 6.1511734e-009

Propagation Delay Odd/Even (seconds/meter):
odd= 6.02475e-009
even= 6.24218e-009

Rdc:
Rdc(Active Signal , Passive Signal) Ohms/Meter
Rdc( ::RectCond1R1 , ::RectCond1R1 )= 1.1428571e+001
Rdc( ::RectCond1R1 , ::RectCond1R0 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R1 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R0 )= 1.1428571e+001

Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )= -1.48130e-003 = -56.58711
dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )= 9.25449e-003 = -40.67295 dB

NOTE: Cross talk results assume there are no reflections.









*
Answered bymike 5 years 14 days
Hi Johan,

Always reset the default CSEG and DSEG from 10 to a much larger value, say
100. This may fix your asymmetry errors. The default settings were probably
set 25 years ago when computers were much slower.

I remember finding some inconsistencies in the TNT output about 20 years ago
but I don't remember the details. I did work with one of the developers at
that time to get results that seemed to makes sense.

You are doing the right things by correlating simulator output to theory. If
you want to extend your correlation efforts you'd have to build coupled L/C
"ladder" networks and make sure your L/C elements have delay (=sqrt(L/C)) about
1/10 of your rise time. LTSpice may or may not have a w-element model but you
can learn a lot more building these ladder networks. For example, you'd build
a subckt of one and chain them together in the main netlist. I may have some
old PERL scripts that extract TNT results and build up spice netlists.

Then you'd have to extend on Istvan's suggestions on termination to provide
near and far end termination networks to terminate all modes. There is some
literature out there on equations for crosstalk with different termination
conditions but I think I've found problems with the FEXT cases.

Regards

Mike Degerstrom


On Sep 2, 2015, at 2:45 AM, Johan Lans wrote:

Hi
Sorry, I should have mentioned that I scaled down the coupling length to
1mm, just to get a more realistic lumped element. Also, I discovered that
TNT was unhappy about the capacitance matrix not being symmetric, so i
added a 75um dielectric layer above the traces, which fixed the problem.
This means somewhat adjusted values:
These are per meter values:
La = L0(1,1) = 3.3022920e-007 H/m
Lv = L0(2,2) = 3.3022920e-007 H/m
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.176

Ca = C0(2,1) + C0(1,1) = 1.12412737e-10 F/m
Cv = C0(2,1) + C0(1,1) = 1.12412737e-10 F/m
Cav = -1*C0(2,1) = 2.5099933e-011 F

Ra = R0(1,1) = 11.4286 Ohm/m
Rv = R0(2,2) = 11.4286 Ohm/m



I didn't know about crosstalk coefficients. Are you using the definitions
on this page for the calculations:
http://www.polarinstruments.com/support/si/AP8164.html ?? Anyway, the
coefficients are obviously normalized to length, so my rescaling shouldn't
matter.

Using the updated values above I get (using definition from polar page):
Kb = 0.25*(2.5099933e-011/1.12412737e-10 + 0.176) = 0.10
Kf = (Cm/C-Lm/L) = 2.5099933e-011/1.12412737e-10 - 0.176 = 0.047


Is this in line with your calculations?

Also, I played around with an evaluation of Polar SI9000. With the same
stackup I get a very similiar RGLC-matrices, but it also reports this:


Kb(NEXT) Kf FEXT
8,938337E-02 1,962233E-11 1,962233E-04

At least Kb seems to match...

TNT reports this:
Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )= 2.30877e-007 = -132.73240 dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )= 1.18904e-005 = -98.49607 dB



Here is a link to my LTSpice model:

https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk2.asc


Many thanks for the help

/Johan




2015-09-02 4:07 GMT+02:00 Istvan Novak :

Hi Johan,

Are you still using the L and C matrix values from your first posting?
With those numbers you can calculate the Kb backward crosstalk coefficient
and Kf forward crosstalk coefficient and they come out 0.0625 and 0.025,
respectively. LTSPICE is pretty accurate if the input models are correct.
E-mail me offline the LTSPICE deck.

Regards,
Istvan







On 9/1/2015 9:14 AM, Johan Lans wrote:

Hi
Well, yes and no. I have simulated propagation delay on the transmission
line (one lump LGCR) in LTSpice with parameters from TNT, and they are
spot
on the same as TNT reports them. This makes me think that the Spice model
is good. However, TNT reports NEXT and FEXT values to be quite different
than what I'm getting from LTSpice. TNT FEXT -92.7dB=, TNT NEXT =-58.5dB,
LTSpice FEXT = -273dB, LTSpice NEXT = -226dB.
A problem is now that I don't know how TNT calculates crosstalk levels. In
LTSpice I'm also getting quite a lot of overshoot and ringing in the
victim, which might indicate a problem with accuracy in LTSice (?).
My next step is to get an evaluation copy of Si9000, from Polar. I read
that it too exports LGCR-parameters, so I can then expirement with those
parameters aswell. I'm thinking that the Polar tool is well trusted and
can
be used as a reference to both LTSpice and TNT.
Best Regards, Johan

2015-09-01 14:38 GMT+02:00 Istvan Novak :

Hi Johan,

I am glad you found it useful.
Does it work now? Do you get the expected answer?

Regards,
Istvan





On 9/1/2015 8:24 AM, Johan Lans wrote:

Great answer, thank you very much.
Johan
Den 31 aug 2015 04:47 skrev "Istvan Novak" :

Johan,

There are a few things that you will need to change to make this work.
To get near end and far end crosstalk, you need four ports that you may
want to terminate in its average characteristic impedance: the
geometric
mean of even and odd mode impedances). Though you may not be
interested
in
delay and length, the way how the numbers are supplied, refer to a
particular length, so your circuit will be a four port circuit. You
need
to check the field solver, what unit length it assumes. From the L
and C
numbers you quote, it may be one meter. The characteristic impedance
from
these L and C numbers appears to be close to 50 ohms, so the Ra and Rv
numbers may represent the losses. If you want a lossless equivalent
circuit, you can replace those numbers with zero, but you have to add
the
proper termination at all four ports. Finally, this is a single-lump
equivalent circuit, because you have one lumped capacitance and one
lumped
inductance for the entire length. As a minimum, you may want to split
the
capacitance values into two (half values) and place them at the input
and
output instead of just being at the output. if you really want a
wideband
model, you will need more lumps.

Hope this will get you going.

Regards,

Istvan Novak
Oracle



On 8/28/2015 3:36 AM, Johan Lans wrote:

Hi

First of all, condolences to everyone who knew Steve Weir. I
referenced
his
work in my masters thesis in physics a few years ago.
I'm trying to understand simulation of crosstalk by doing some field
solving of a trace pair using MMTL (the Multilayer Multiconductor
Transmission Line 2-D and 2.5-D electromagnetic modelling tool suite,
http://mmtl.sourceforge.net/). The solver can output an HSpice
w-element
model of the signal pair, and I'm trying to replicate the crosstalk
levels
reported by the solver by setting up an equivalent circuit in LTSpice.
However, I am not quite sure how to translate all the details into an
equivalent circuit, so if I walk through my thought process doing
this,
maybe someone can point if I'm doing anything wrong?
In the end of this email, I'm pasting the solver output from TNT
1.2.2,
as
well as the w-element output.
The Spice model is a simple RLGC-model. One for the aggressor (I'll
call
the components Ra, Ca and so on)and one for the victim (Rv, Cv ..),
with
an
extra capacitor for coupling between the two circuits (Cav). The
inductors
are coupled using a coupling factor. A link to the LTSpice design is
here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.asc
Following Eric Bogatins chapter on crosstalk in "Signal and Power
Integrity
Simplified, 2nd ed", I came up with the values like this: From the
w-element file,

La = L0(1,1) = 3.29962e-007 H
Lv = L0(2,2) = 3.29953e-007 H
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.175

Ca = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cv = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cav = -1*C0(2,1) = 1.49773e-011 F

Ra = R0(1,1) = 11.4286 Ohm
Rv = R0(2,2) = 11.4286 Ohm

G0 and Gd is zero, and I omitted Rs , since I'm not really interested
in
losses right now.

TNT calculates fare end crosstalk to and near end crosstalk to . I'm
not
sure how to translate this to measurements in LTSpice, but I injected
a
1V,
100ns, step into the aggressors resistor and measured how much signal
was
crosstalked over at the Cav end of the victim circuit (a bit difficult
to
explain without schematic, but here's a screen capture from LTSpice:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.png) The
crosstalked signal has an amplitude of about 18mV, which is about
-55dB. I
interpret this as being near end crosstalk, since there is no actual
length
in the model. The field solver reports near end crosstalk to be -41dB,
but
far end crosstalk to be -57dB.

Am I doing anything right here?


Thanks in advance from
Johan



As reference, the field solver files are here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.xsctn
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.result
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.hspice-w.rlgc




2015 08 28 09:12:31 johan.lans NMMTL_2DLF

File = C:/Program Files (x86)/tnt-1.2.2/examples/xtalk
Number of Signal Lines = 2
Number of Ground Planes = 1
Number of Ground Wires = 0
Coupling Length = 1.00000 meters
Rise Time = 100000.0012 picoseconds
Contour (conductor) segments [cseg] = 10
Ground Plane/Dielectric segments [dseg] = 10
Conductivity RectCond1R1 = 5e+007 siemens/meter
Conductivity RectCond1R0 = 5e+007 siemens/meter
Note: minimum frequency for surface current assumptions is 1655 MHz.
Mutual and Self Electrostatic Induction:
B(Active Signal , Passive Signal) Farads/Meter
B( ::RectCond1R1 , ::RectCond1R1 )= 1.1691868e-010
B( ::RectCond1R1 , ::RectCond1R0 )= -1.6413763e-011
B( ::RectCond1R0 , ::RectCond1R1 )= -1.4977254e-011
B( ::RectCond1R0 , ::RectCond1R0 )= 1.1813248e-010

Mutual and Self Inductance:
L(Active Signal , Passive Signal) Henrys/Meter
L( ::RectCond1R1 , ::RectCond1R1 )= 3.2996223e-007
L( ::RectCond1R1 , ::RectCond1R0 )= 5.7727959e-008
L( ::RectCond1R0 , ::RectCond1R1 )= 5.7747599e-008
L( ::RectCond1R0 , ::RectCond1R0 )= 3.2995263e-007

Asymmetry Ratios:

Asymmetry ratio for inductance matrix:
0.034021% (max), 0.034021% (average)

**********
Asymmetry ratio for electrostatic induction matrix:
8.751856% (max), 8.751856% (average).
(Note values greater than 1% are a probable indication of too few
elements.
Try adjusting CSEG and DSEG attributes.)
**********

Characteristic Impedance (Ohms):
For Signal Line ::RectCond1R1= 53.1239
For Signal Line ::RectCond1R0= 52.8495

Characteristic Impedance Odd/Even (Ohms):
odd= 45.186
even= 62.1082

Effective Dielectric Constant:
For Signal Line ::RectCond1R1= 3.36577
For Signal Line ::RectCond1R0= 3.40061

Propagation Velocity (meters/second):
For Signal Line ::RectCond1R1= 1.6340992e+008
For Signal Line ::RectCond1R0= 1.6257061e+008

Propagation Velocity Odd/Even (meters/second):
odd= 1.65982e+008
even= 1.60201e+008

Propagation Delay (seconds/meter):
For Signal Line ::RectCond1R1= 6.1195795e-009
For Signal Line ::RectCond1R0= 6.1511734e-009

Propagation Delay Odd/Even (seconds/meter):
odd= 6.02475e-009
even= 6.24218e-009

Rdc:
Rdc(Active Signal , Passive Signal) Ohms/Meter
Rdc( ::RectCond1R1 , ::RectCond1R1 )= 1.1428571e+001
Rdc( ::RectCond1R1 , ::RectCond1R0 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R1 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R0 )= 1.1428571e+001

Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )= -1.48130e-003 = -56.58711 dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )= 9.25449e-003 = -40.67295 dB

NOTE: Cross talk results assume there are no reflections.









*
Answered byistvan.novak 5 years 15 days
Johan,
Your LTSPICE circuit does not provide matching at the source. You have
a voltage source and the termination is in the shunt leg. Either you
have to use a current source, or If you use voltage source, you need to
change to series termination (only at the source). Also, when you use a
1mm length, the corresponding delay is a few ps; with a 100ns PWL edge
you dont get much crosstalk at either end, this is the reason for the
big difference.

Regards,

Istvan Novak
Oracle

On 9/2/2015 3:45 AM, Johan Lans wrote:
Hi
Sorry, I should have mentioned that I scaled down the coupling length
to 1mm, just to get a more realistic lumped element. Also, I
discovered that TNT was unhappy about the capacitance matrix not being
symmetric, so i added a 75um dielectric layer above the traces, which
fixed the problem. This means somewhat adjusted values:

These are per meter values:
La = L0(1,1) = 3.3022920e-007 H/m
Lv = L0(2,2) = 3.3022920e-007 H/m
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.176

Ca = C0(2,1) + C0(1,1) = 1.12412737e-10 F/m
Cv = C0(2,1) + C0(1,1) = 1.12412737e-10 F/m
Cav = -1*C0(2,1) = 2.5099933e-011 F

Ra = R0(1,1) = 11.4286 Ohm/m
Rv = R0(2,2) = 11.4286 Ohm/m



I didn't know about crosstalk coefficients. Are you using the
definitions on this page for the calculations:
http://www.polarinstruments.com/support/si/AP8164.html ?? Anyway, the
coefficients are obviously normalized to length, so my rescaling
shouldn't matter.

Using the updated values above I get (using definition from polar page):
Kb = 0.25*(2.5099933e-011/1.12412737e-10 + 0.176) = 0.10
Kf = (Cm/C-Lm/L) = 2.5099933e-011/1.12412737e-10 - 0.176 = 0.047


Is this in line with your calculations?

Also, I played around with an evaluation of Polar SI9000. With the
same stackup I get a very similiar RGLC-matrices, but it also reports
this:


Kb(NEXT)KfFEXT
8,938337E-021,962233E-111,962233E-04

At least Kb seems to match...

TNT reports this:
Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )= 2.30877e-007 = -132.73240 dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )= 1.18904e-005 = -98.49607 dB



Here is a link to my LTSpice model:

https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk2.asc


Many thanks for the help

/Johan




2015-09-02 4:07 GMT+02:00 Istvan Novak >:

Hi Johan,

Are you still using the L and C matrix values from your first posting?
With those numbers you can calculate the Kb backward crosstalk
coefficient and Kf forward crosstalk coefficient and they come out
0.0625 and 0.025, respectively. LTSPICE is pretty accurate if the
input models are correct. E-mail me offline the LTSPICE deck.

Regards,
Istvan







On 9/1/2015 9:14 AM, Johan Lans wrote:

Hi
Well, yes and no. I have simulated propagation delay on the
transmission
line (one lump LGCR) in LTSpice with parameters from TNT, and
they are spot
on the same as TNT reports them. This makes me think that the
Spice model
is good. However, TNT reports NEXT and FEXT values to be quite
different
than what I'm getting from LTSpice. TNT FEXT -92.7dB=, TNT
NEXT =-58.5dB,
LTSpice FEXT = -273dB, LTSpice NEXT = -226dB.
A problem is now that I don't know how TNT calculates
crosstalk levels. In
LTSpice I'm also getting quite a lot of overshoot and ringing
in the
victim, which might indicate a problem with accuracy in LTSice
(?).
My next step is to get an evaluation copy of Si9000, from
Polar. I read
that it too exports LGCR-parameters, so I can then expirement
with those
parameters aswell. I'm thinking that the Polar tool is well
trusted and can
be used as a reference to both LTSpice and TNT.
Best Regards, Johan

2015-09-01 14:38 GMT+02:00 Istvan Novak
>:

Hi Johan,

I am glad you found it useful.
Does it work now? Do you get the expected answer?

Regards,
Istvan





On 9/1/2015 8:24 AM, Johan Lans wrote:

Great answer, thank you very much.
Johan
Den 31 aug 2015 04:47 skrev "Istvan Novak"
>:

Johan,

There are a few things that you will need to
change to make this work.
To get near end and far end crosstalk, you need
four ports that you may
want to terminate in its average characteristic
impedance: the geometric
mean of even and odd mode impedances). Though you
may not be interested
in
delay and length, the way how the numbers are
supplied, refer to a
particular length, so your circuit will be a four
port circuit. You need
to check the field solver, what unit length it
assumes. From the L and C
numbers you quote, it may be one meter. The
characteristic impedance
from
these L and C numbers appears to be close to 50
ohms, so the Ra and Rv
numbers may represent the losses. If you want a
lossless equivalent
circuit, you can replace those numbers with zero,
but you have to add the
proper termination at all four ports. Finally,
this is a single-lump
equivalent circuit, because you have one lumped
capacitance and one
lumped
inductance for the entire length. As a minimum,
you may want to split
the
capacitance values into two (half values) and
place them at the input and
output instead of just being at the output. if
you really want a
wideband
model, you will need more lumps.

Hope this will get you going.

Regards,

Istvan Novak
Oracle



On 8/28/2015 3:36 AM, Johan Lans wrote:

Hi

First of all, condolences to everyone who knew
Steve Weir. I referenced
his
work in my masters thesis in physics a few
years ago.
I'm trying to understand simulation of
crosstalk by doing some field
solving of a trace pair using MMTL (the
Multilayer Multiconductor
Transmission Line 2-D and 2.5-D
electromagnetic modelling tool suite,
http://mmtl.sourceforge.net/). The solver can
output an HSpice
w-element
model of the signal pair, and I'm trying to
replicate the crosstalk
levels
reported by the solver by setting up an
equivalent circuit in LTSpice.
However, I am not quite sure how to translate
all the details into an
equivalent circuit, so if I walk through my
thought process doing this,
maybe someone can point if I'm doing anything
wrong?
In the end of this email, I'm pasting the
solver output from TNT 1.2.2,
as
well as the w-element output.
The Spice model is a simple RLGC-model. One
for the aggressor (I'll call
the components Ra, Ca and so on)and one for
the victim (Rv, Cv ..), with
an
extra capacitor for coupling between the two
circuits (Cav). The
inductors
are coupled using a coupling factor. A link to
the LTSpice design is
here:

https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.asc
Following Eric Bogatins chapter on crosstalk
in "Signal and Power
Integrity
Simplified, 2nd ed", I came up with the values
like this: From the
w-element file,

La = L0(1,1) = 3.29962e-007 H
Lv = L0(2,2) = 3.29953e-007 H
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.175

Ca = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cv = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cav = -1*C0(2,1) = 1.49773e-011 F

Ra = R0(1,1) = 11.4286 Ohm
Rv = R0(2,2) = 11.4286 Ohm

G0 and Gd is zero, and I omitted Rs , since
I'm not really interested in
losses right now.

TNT calculates fare end crosstalk to and near
end crosstalk to . I'm not
sure how to translate this to measurements in
LTSpice, but I injected a
1V,
100ns, step into the aggressors resistor and
measured how much signal
was
crosstalked over at the Cav end of the victim
circuit (a bit difficult
to
explain without schematic, but here's a screen
capture from LTSpice:

https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.png)
The
crosstalked signal has an amplitude of about
18mV, which is about
-55dB. I
interpret this as being near end crosstalk,
since there is no actual
length
in the model. The field solver reports near
end crosstalk to be -41dB,
but
far end crosstalk to be -57dB.

Am I doing anything right here?


Thanks in advance from
Johan



As reference, the field solver files are here:

https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.xsctn

https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.result

https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.hspice-w.rlgc




2015 08 28 09 :12:31
johan.lans NMMTL_2DLF

File = C:/Program Files
(x86)/tnt-1.2.2/examples/xtalk
Number of Signal Lines = 2
Number of Ground Planes = 1
Number of Ground Wires = 0
Coupling Length = 1.00000 meters
Rise Time = 100000.0012 picoseconds
Contour (conductor) segments [cseg] = 10
Ground Plane/Dielectric segments [dseg] = 10
Conductivity RectCond1R1 = 5e+007 siemens/meter
Conductivity RectCond1R0 = 5e+007 siemens/meter
Note: minimum frequency for surface current
assumptions is 1655 MHz.
Mutual and Self Electrostatic Induction:
B(Active Signal , Passive Signal) Farads/Meter
B( ::RectCond1R1 , ::RectCond1R1 )= 1.1691868e-010
B( ::RectCond1R1 , ::RectCond1R0 )=
-1.6413763e-011
B( ::RectCond1R0 , ::RectCond1R1 )=
-1.4977254e-011
B( ::RectCond1R0 , ::RectCond1R0 )= 1.1813248e-010

Mutual and Self Inductance:
L(Active Signal , Passive Signal) Henrys/Meter
L( ::RectCond1R1 , ::RectCond1R1 )= 3.2996223e-007
L( ::RectCond1R1 , ::RectCond1R0 )= 5.7727959e-008
L( ::RectCond1R0 , ::RectCond1R1 )= 5.7747599e-008
L( ::RectCond1R0 , ::RectCond1R0 )= 3.2995263e-007

Asymmetry Ratios:

Asymmetry ratio for inductance matrix:
0.034021% (max), 0.034021% (average)

**********
Asymmetry ratio for electrostatic
induction matrix:
8.751856% (max), 8.751856% (average).
(Note values greater than 1% are a
probable indication of too few
elements.
Try adjusting CSEG and DSEG attributes.)
**********

Characteristic Impedance (Ohms):
For Signal Line ::RectCond1R1= 53.1239
For Signal Line ::RectCond1R0= 52.8495

Characteristic Impedance Odd/Even (Ohms):
odd= 45.186
even= 62.1082

Effective Dielectric Constant:
For Signal Line ::RectCond1R1= 3.36577
For Signal Line ::RectCond1R0= 3.40061

Propagation Velocity (meters/second):
For Signal Line ::RectCond1R1= 1.6340992e+008
For Signal Line ::RectCond1R0= 1.6257061e+008

Propagation Velocity Odd/Even (meters/second):
odd= 1.65982e+008
even= 1.60201e+008

Propagation Delay (seconds/meter):
For Signal Line ::RectCond1R1= 6.1195795e-009
For Signal Line ::RectCond1R0= 6.1511734e-009

Propagation Delay Odd/Even (seconds/meter):
odd= 6.02475e-009
even= 6.24218e-009

Rdc:
Rdc(Active Signal , Passive Signal) Ohms/Meter
Rdc( ::RectCond1R1 , ::RectCond1R1 )=
1.1428571e+001
Rdc( ::RectCond1R1 , ::RectCond1R0 )=
0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R1 )=
0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R0 )=
1.1428571e+001

Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )=
-1.48130e-003 = -56.58711 dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )=
9.25449e-003 = -40.67295 dB

NOTE: Cross talk results assume there are no
reflections.









*
Answered byjohan.lans 5 years 16 days
Hi
Sorry, I should have mentioned that I scaled down the coupling length to
1mm, just to get a more realistic lumped element. Also, I discovered that
TNT was unhappy about the capacitance matrix not being symmetric, so i
added a 75um dielectric layer above the traces, which fixed the problem.
This means somewhat adjusted values:
These are per meter values:
La = L0(1,1) = 3.3022920e-007 H/m
Lv = L0(2,2) = 3.3022920e-007 H/m
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.176

Ca = C0(2,1) + C0(1,1) = 1.12412737e-10 F/m
Cv = C0(2,1) + C0(1,1) = 1.12412737e-10 F/m
Cav = -1*C0(2,1) = 2.5099933e-011 F

Ra = R0(1,1) = 11.4286 Ohm/m
Rv = R0(2,2) = 11.4286 Ohm/m



I didn't know about crosstalk coefficients. Are you using the definitions
on this page for the calculations:
http://www.polarinstruments.com/support/si/AP8164.html ?? Anyway, the
coefficients are obviously normalized to length, so my rescaling shouldn't
matter.

Using the updated values above I get (using definition from polar page):
Kb = 0.25*(2.5099933e-011/1.12412737e-10 + 0.176) = 0.10
Kf = (Cm/C-Lm/L) = 2.5099933e-011/1.12412737e-10 - 0.176 = 0.047


Is this in line with your calculations?

Also, I played around with an evaluation of Polar SI9000. With the same
stackup I get a very similiar RGLC-matrices, but it also reports this:


Kb(NEXT) Kf FEXT
8,938337E-02 1,962233E-11 1,962233E-04

At least Kb seems to match...

TNT reports this:
Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )= 2.30877e-007 = -132.73240 dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )= 1.18904e-005 = -98.49607 dB



Here is a link to my LTSpice model:

https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk2.asc


Many thanks for the help

/Johan




2015-09-02 4:07 GMT+02:00 Istvan Novak :

Hi Johan,

Are you still using the L and C matrix values from your first posting?
With those numbers you can calculate the Kb backward crosstalk coefficient
and Kf forward crosstalk coefficient and they come out 0.0625 and 0.025,
respectively. LTSPICE is pretty accurate if the input models are correct.
E-mail me offline the LTSPICE deck.

Regards,
Istvan







On 9/1/2015 9:14 AM, Johan Lans wrote:

Hi
Well, yes and no. I have simulated propagation delay on the transmission
line (one lump LGCR) in LTSpice with parameters from TNT, and they are
spot
on the same as TNT reports them. This makes me think that the Spice model
is good. However, TNT reports NEXT and FEXT values to be quite different
than what I'm getting from LTSpice. TNT FEXT -92.7dB=, TNT NEXT =-58.5dB,
LTSpice FEXT = -273dB, LTSpice NEXT = -226dB.
A problem is now that I don't know how TNT calculates crosstalk levels. In
LTSpice I'm also getting quite a lot of overshoot and ringing in the
victim, which might indicate a problem with accuracy in LTSice (?).
My next step is to get an evaluation copy of Si9000, from Polar. I read
that it too exports LGCR-parameters, so I can then expirement with those
parameters aswell. I'm thinking that the Polar tool is well trusted and
can
be used as a reference to both LTSpice and TNT.
Best Regards, Johan

2015-09-01 14:38 GMT+02:00 Istvan Novak :

Hi Johan,

I am glad you found it useful.
Does it work now? Do you get the expected answer?

Regards,
Istvan





On 9/1/2015 8:24 AM, Johan Lans wrote:

Great answer, thank you very much.
Johan
Den 31 aug 2015 04:47 skrev "Istvan Novak" :

Johan,

There are a few things that you will need to change to make this work.
To get near end and far end crosstalk, you need four ports that you may
want to terminate in its average characteristic impedance: the
geometric
mean of even and odd mode impedances). Though you may not be
interested
in
delay and length, the way how the numbers are supplied, refer to a
particular length, so your circuit will be a four port circuit. You
need
to check the field solver, what unit length it assumes. From the L
and C
numbers you quote, it may be one meter. The characteristic impedance
from
these L and C numbers appears to be close to 50 ohms, so the Ra and Rv
numbers may represent the losses. If you want a lossless equivalent
circuit, you can replace those numbers with zero, but you have to add
the
proper termination at all four ports. Finally, this is a single-lump
equivalent circuit, because you have one lumped capacitance and one
lumped
inductance for the entire length. As a minimum, you may want to split
the
capacitance values into two (half values) and place them at the input
and
output instead of just being at the output. if you really want a
wideband
model, you will need more lumps.

Hope this will get you going.

Regards,

Istvan Novak
Oracle



On 8/28/2015 3:36 AM, Johan Lans wrote:

Hi

First of all, condolences to everyone who knew Steve Weir. I
referenced
his
work in my masters thesis in physics a few years ago.
I'm trying to understand simulation of crosstalk by doing some field
solving of a trace pair using MMTL (the Multilayer Multiconductor
Transmission Line 2-D and 2.5-D electromagnetic modelling tool suite,
http://mmtl.sourceforge.net/). The solver can output an HSpice
w-element
model of the signal pair, and I'm trying to replicate the crosstalk
levels
reported by the solver by setting up an equivalent circuit in LTSpice.
However, I am not quite sure how to translate all the details into an
equivalent circuit, so if I walk through my thought process doing
this,
maybe someone can point if I'm doing anything wrong?
In the end of this email, I'm pasting the solver output from TNT
1.2.2,
as
well as the w-element output.
The Spice model is a simple RLGC-model. One for the aggressor (I'll
call
the components Ra, Ca and so on)and one for the victim (Rv, Cv ..),
with
an
extra capacitor for coupling between the two circuits (Cav). The
inductors
are coupled using a coupling factor. A link to the LTSpice design is
here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.asc
Following Eric Bogatins chapter on crosstalk in "Signal and Power
Integrity
Simplified, 2nd ed", I came up with the values like this: From the
w-element file,

La = L0(1,1) = 3.29962e-007 H
Lv = L0(2,2) = 3.29953e-007 H
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.175

Ca = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cv = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cav = -1*C0(2,1) = 1.49773e-011 F

Ra = R0(1,1) = 11.4286 Ohm
Rv = R0(2,2) = 11.4286 Ohm

G0 and Gd is zero, and I omitted Rs , since I'm not really interested
in
losses right now.

TNT calculates fare end crosstalk to and near end crosstalk to . I'm
not
sure how to translate this to measurements in LTSpice, but I injected
a
1V,
100ns, step into the aggressors resistor and measured how much signal
was
crosstalked over at the Cav end of the victim circuit (a bit difficult
to
explain without schematic, but here's a screen capture from LTSpice:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.png) The
crosstalked signal has an amplitude of about 18mV, which is about
-55dB. I
interpret this as being near end crosstalk, since there is no actual
length
in the model. The field solver reports near end crosstalk to be -41dB,
but
far end crosstalk to be -57dB.

Am I doing anything right here?


Thanks in advance from
Johan



As reference, the field solver files are here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.xsctn
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.result
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.hspice-w.rlgc




2015 08 28 09:12:31 johan.lans NMMTL_2DLF

File = C:/Program Files (x86)/tnt-1.2.2/examples/xtalk
Number of Signal Lines = 2
Number of Ground Planes = 1
Number of Ground Wires = 0
Coupling Length = 1.00000 meters
Rise Time = 100000.0012 picoseconds
Contour (conductor) segments [cseg] = 10
Ground Plane/Dielectric segments [dseg] = 10
Conductivity RectCond1R1 = 5e+007 siemens/meter
Conductivity RectCond1R0 = 5e+007 siemens/meter
Note: minimum frequency for surface current assumptions is 1655 MHz.
Mutual and Self Electrostatic Induction:
B(Active Signal , Passive Signal) Farads/Meter
B( ::RectCond1R1 , ::RectCond1R1 )= 1.1691868e-010
B( ::RectCond1R1 , ::RectCond1R0 )= -1.6413763e-011
B( ::RectCond1R0 , ::RectCond1R1 )= -1.4977254e-011
B( ::RectCond1R0 , ::RectCond1R0 )= 1.1813248e-010

Mutual and Self Inductance:
L(Active Signal , Passive Signal) Henrys/Meter
L( ::RectCond1R1 , ::RectCond1R1 )= 3.2996223e-007
L( ::RectCond1R1 , ::RectCond1R0 )= 5.7727959e-008
L( ::RectCond1R0 , ::RectCond1R1 )= 5.7747599e-008
L( ::RectCond1R0 , ::RectCond1R0 )= 3.2995263e-007

Asymmetry Ratios:

Asymmetry ratio for inductance matrix:
0.034021% (max), 0.034021% (average)

**********
Asymmetry ratio for electrostatic induction matrix:
8.751856% (max), 8.751856% (average).
(Note values greater than 1% are a probable indication of too few
elements.
Try adjusting CSEG and DSEG attributes.)
**********

Characteristic Impedance (Ohms):
For Signal Line ::RectCond1R1= 53.1239
For Signal Line ::RectCond1R0= 52.8495

Characteristic Impedance Odd/Even (Ohms):
odd= 45.186
even= 62.1082

Effective Dielectric Constant:
For Signal Line ::RectCond1R1= 3.36577
For Signal Line ::RectCond1R0= 3.40061

Propagation Velocity (meters/second):
For Signal Line ::RectCond1R1= 1.6340992e+008
For Signal Line ::RectCond1R0= 1.6257061e+008

Propagation Velocity Odd/Even (meters/second):
odd= 1.65982e+008
even= 1.60201e+008

Propagation Delay (seconds/meter):
For Signal Line ::RectCond1R1= 6.1195795e-009
For Signal Line ::RectCond1R0= 6.1511734e-009

Propagation Delay Odd/Even (seconds/meter):
odd= 6.02475e-009
even= 6.24218e-009

Rdc:
Rdc(Active Signal , Passive Signal) Ohms/Meter
Rdc( ::RectCond1R1 , ::RectCond1R1 )= 1.1428571e+001
Rdc( ::RectCond1R1 , ::RectCond1R0 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R1 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R0 )= 1.1428571e+001

Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )= -1.48130e-003 = -56.58711 dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )= 9.25449e-003 = -40.67295 dB

NOTE: Cross talk results assume there are no reflections.









*
Answered bysammy.a.hindi 5 years 16 days
Are you interested in strip line or micro strip line calculation?
Regards,
Sammy

On Tuesday, September 1, 2015, Aubrey Sparkman <
asparky@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:

Hi Johan,

I have on caution for you. While most 2D solvers / simulators do a good
job with impedance and near end crosstalk, few do well with far end
crosstalk. How do you know which answer is correct?

Aubrey

Sent from my iPhone

On Sep 1, 2015, at 8:14 AM, Johan Lans > wrote:

Hi
Well, yes and no. I have simulated propagation delay on the transmission
line (one lump LGCR) in LTSpice with parameters from TNT, and they are
spot
on the same as TNT reports them. This makes me think that the Spice model
is good. However, TNT reports NEXT and FEXT values to be quite different
than what I'm getting from LTSpice. TNT FEXT -92.7dB=, TNT NEXT =-58.5dB,
LTSpice FEXT = -273dB, LTSpice NEXT = -226dB.
A problem is now that I don't know how TNT calculates crosstalk levels.
In
LTSpice I'm also getting quite a lot of overshoot and ringing in the
victim, which might indicate a problem with accuracy in LTSice (?).
My next step is to get an evaluation copy of Si9000, from Polar. I read
that it too exports LGCR-parameters, so I can then expirement with those
parameters aswell. I'm thinking that the Polar tool is well trusted and
can
be used as a reference to both LTSpice and TNT.
Best Regards, Johan

2015-09-01 14:38 GMT+02:00 Istvan Novak >:

Hi Johan,

I am glad you found it useful.
Does it work now? Do you get the expected answer?

Regards,
Istvan





On 9/1/2015 8:24 AM, Johan Lans wrote:

Great answer, thank you very much.
Johan
Den 31 aug 2015 04:47 skrev "Istvan Novak" >:

Johan,

There are a few things that you will need to change to make this work.
To get near end and far end crosstalk, you need four ports that you
may

Answered byasparky 5 years 17 days
Hi Johan,

I have on caution for you. While most 2D solvers / simulators do a good job
with impedance and near end crosstalk, few do well with far end crosstalk.
How do you know which answer is correct?

Aubrey

Sent from my iPhone

On Sep 1, 2015, at 8:14 AM, Johan Lans wrote:

Hi
Well, yes and no. I have simulated propagation delay on the transmission
line (one lump LGCR) in LTSpice with parameters from TNT, and they are spot
on the same as TNT reports them. This makes me think that the Spice model
is good. However, TNT reports NEXT and FEXT values to be quite different
than what I'm getting from LTSpice. TNT FEXT -92.7dB=, TNT NEXT =-58.5dB,
LTSpice FEXT = -273dB, LTSpice NEXT = -226dB.
A problem is now that I don't know how TNT calculates crosstalk levels. In
LTSpice I'm also getting quite a lot of overshoot and ringing in the
victim, which might indicate a problem with accuracy in LTSice (?).
My next step is to get an evaluation copy of Si9000, from Polar. I read
that it too exports LGCR-parameters, so I can then expirement with those
parameters aswell. I'm thinking that the Polar tool is well trusted and can
be used as a reference to both LTSpice and TNT.
Best Regards, Johan

2015-09-01 14:38 GMT+02:00 Istvan Novak :

Hi Johan,

I am glad you found it useful.
Does it work now? Do you get the expected answer?

Regards,
Istvan





On 9/1/2015 8:24 AM, Johan Lans wrote:

Great answer, thank you very much.
Johan
Den 31 aug 2015 04:47 skrev "Istvan Novak" :

Johan,

There are a few things that you will need to change to make this work.
To get near end and far end crosstalk, you need four ports that you may

Answered byjohan.lans 5 years 17 days
Hi
Well, yes and no. I have simulated propagation delay on the transmission
line (one lump LGCR) in LTSpice with parameters from TNT, and they are spot
on the same as TNT reports them. This makes me think that the Spice model
is good. However, TNT reports NEXT and FEXT values to be quite different
than what I'm getting from LTSpice. TNT FEXT -92.7dB=, TNT NEXT =-58.5dB,
LTSpice FEXT = -273dB, LTSpice NEXT = -226dB.
A problem is now that I don't know how TNT calculates crosstalk levels. In
LTSpice I'm also getting quite a lot of overshoot and ringing in the
victim, which might indicate a problem with accuracy in LTSice (?).
My next step is to get an evaluation copy of Si9000, from Polar. I read
that it too exports LGCR-parameters, so I can then expirement with those
parameters aswell. I'm thinking that the Polar tool is well trusted and can
be used as a reference to both LTSpice and TNT.
Best Regards, Johan

2015-09-01 14:38 GMT+02:00 Istvan Novak :

Hi Johan,

I am glad you found it useful.
Does it work now? Do you get the expected answer?

Regards,
Istvan





On 9/1/2015 8:24 AM, Johan Lans wrote:

Great answer, thank you very much.
Johan
Den 31 aug 2015 04:47 skrev "Istvan Novak" :

Johan,

There are a few things that you will need to change to make this work.
To get near end and far end crosstalk, you need four ports that you may
want to terminate in its average characteristic impedance: the geometric
mean of even and odd mode impedances). Though you may not be interested
in
delay and length, the way how the numbers are supplied, refer to a
particular length, so your circuit will be a four port circuit. You need
to check the field solver, what unit length it assumes. From the L and C
numbers you quote, it may be one meter. The characteristic impedance
from
these L and C numbers appears to be close to 50 ohms, so the Ra and Rv
numbers may represent the losses. If you want a lossless equivalent
circuit, you can replace those numbers with zero, but you have to add the
proper termination at all four ports. Finally, this is a single-lump
equivalent circuit, because you have one lumped capacitance and one
lumped
inductance for the entire length. As a minimum, you may want to split
the
capacitance values into two (half values) and place them at the input and
output instead of just being at the output. if you really want a
wideband
model, you will need more lumps.

Hope this will get you going.

Regards,

Istvan Novak
Oracle



On 8/28/2015 3:36 AM, Johan Lans wrote:

Hi
First of all, condolences to everyone who knew Steve Weir. I referenced
his
work in my masters thesis in physics a few years ago.
I'm trying to understand simulation of crosstalk by doing some field
solving of a trace pair using MMTL (the Multilayer Multiconductor
Transmission Line 2-D and 2.5-D electromagnetic modelling tool suite,
http://mmtl.sourceforge.net/). The solver can output an HSpice
w-element
model of the signal pair, and I'm trying to replicate the crosstalk
levels
reported by the solver by setting up an equivalent circuit in LTSpice.
However, I am not quite sure how to translate all the details into an
equivalent circuit, so if I walk through my thought process doing this,
maybe someone can point if I'm doing anything wrong?
In the end of this email, I'm pasting the solver output from TNT 1.2.2,
as
well as the w-element output.
The Spice model is a simple RLGC-model. One for the aggressor (I'll call
the components Ra, Ca and so on)and one for the victim (Rv, Cv ..), with
an
extra capacitor for coupling between the two circuits (Cav). The
inductors
are coupled using a coupling factor. A link to the LTSpice design is
here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.asc
Following Eric Bogatins chapter on crosstalk in "Signal and Power
Integrity
Simplified, 2nd ed", I came up with the values like this: From the
w-element file,

La = L0(1,1) = 3.29962e-007 H
Lv = L0(2,2) = 3.29953e-007 H
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.175

Ca = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cv = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cav = -1*C0(2,1) = 1.49773e-011 F

Ra = R0(1,1) = 11.4286 Ohm
Rv = R0(2,2) = 11.4286 Ohm

G0 and Gd is zero, and I omitted Rs , since I'm not really interested in
losses right now.

TNT calculates fare end crosstalk to and near end crosstalk to . I'm not
sure how to translate this to measurements in LTSpice, but I injected a
1V,
100ns, step into the aggressors resistor and measured how much signal
was
crosstalked over at the Cav end of the victim circuit (a bit difficult
to
explain without schematic, but here's a screen capture from LTSpice:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.png) The
crosstalked signal has an amplitude of about 18mV, which is about
-55dB. I
interpret this as being near end crosstalk, since there is no actual
length
in the model. The field solver reports near end crosstalk to be -41dB,
but
far end crosstalk to be -57dB.

Am I doing anything right here?


Thanks in advance from
Johan



As reference, the field solver files are here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.xsctn
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.result
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.hspice-w.rlgc




2015 08 28 09:12:31 johan.lans NMMTL_2DLF

File = C:/Program Files (x86)/tnt-1.2.2/examples/xtalk
Number of Signal Lines = 2
Number of Ground Planes = 1
Number of Ground Wires = 0
Coupling Length = 1.00000 meters
Rise Time = 100000.0012 picoseconds
Contour (conductor) segments [cseg] = 10
Ground Plane/Dielectric segments [dseg] = 10
Conductivity RectCond1R1 = 5e+007 siemens/meter
Conductivity RectCond1R0 = 5e+007 siemens/meter
Note: minimum frequency for surface current assumptions is 1655 MHz.
Mutual and Self Electrostatic Induction:
B(Active Signal , Passive Signal) Farads/Meter
B( ::RectCond1R1 , ::RectCond1R1 )= 1.1691868e-010
B( ::RectCond1R1 , ::RectCond1R0 )= -1.6413763e-011
B( ::RectCond1R0 , ::RectCond1R1 )= -1.4977254e-011
B( ::RectCond1R0 , ::RectCond1R0 )= 1.1813248e-010

Mutual and Self Inductance:
L(Active Signal , Passive Signal) Henrys/Meter
L( ::RectCond1R1 , ::RectCond1R1 )= 3.2996223e-007
L( ::RectCond1R1 , ::RectCond1R0 )= 5.7727959e-008
L( ::RectCond1R0 , ::RectCond1R1 )= 5.7747599e-008
L( ::RectCond1R0 , ::RectCond1R0 )= 3.2995263e-007

Asymmetry Ratios:

Asymmetry ratio for inductance matrix:
0.034021% (max), 0.034021% (average)

**********
Asymmetry ratio for electrostatic induction matrix:
8.751856% (max), 8.751856% (average).
(Note values greater than 1% are a probable indication of too few
elements.
Try adjusting CSEG and DSEG attributes.)
**********

Characteristic Impedance (Ohms):
For Signal Line ::RectCond1R1= 53.1239
For Signal Line ::RectCond1R0= 52.8495

Characteristic Impedance Odd/Even (Ohms):
odd= 45.186
even= 62.1082

Effective Dielectric Constant:
For Signal Line ::RectCond1R1= 3.36577
For Signal Line ::RectCond1R0= 3.40061

Propagation Velocity (meters/second):
For Signal Line ::RectCond1R1= 1.6340992e+008
For Signal Line ::RectCond1R0= 1.6257061e+008

Propagation Velocity Odd/Even (meters/second):
odd= 1.65982e+008
even= 1.60201e+008

Propagation Delay (seconds/meter):
For Signal Line ::RectCond1R1= 6.1195795e-009
For Signal Line ::RectCond1R0= 6.1511734e-009

Propagation Delay Odd/Even (seconds/meter):
odd= 6.02475e-009
even= 6.24218e-009

Rdc:
Rdc(Active Signal , Passive Signal) Ohms/Meter
Rdc( ::RectCond1R1 , ::RectCond1R1 )= 1.1428571e+001
Rdc( ::RectCond1R1 , ::RectCond1R0 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R1 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R0 )= 1.1428571e+001

Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )= -1.48130e-003 = -56.58711 dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )= 9.25449e-003 = -40.67295 dB

NOTE: Cross talk results assume there are no reflections.









*
Answered byjohan.lans 5 years 17 days
Great answer, thank you very much.
Johan
Den 31 aug 2015 04:47 skrev "Istvan Novak" :

Johan,

There are a few things that you will need to change to make this work.
To get near end and far end crosstalk, you need four ports that you may
want to terminate in its average characteristic impedance: the geometric
mean of even and odd mode impedances). Though you may not be interested in
delay and length, the way how the numbers are supplied, refer to a
particular length, so your circuit will be a four port circuit. You need
to check the field solver, what unit length it assumes. From the L and C
numbers you quote, it may be one meter. The characteristic impedance from
these L and C numbers appears to be close to 50 ohms, so the Ra and Rv
numbers may represent the losses. If you want a lossless equivalent
circuit, you can replace those numbers with zero, but you have to add the
proper termination at all four ports. Finally, this is a single-lump
equivalent circuit, because you have one lumped capacitance and one lumped
inductance for the entire length. As a minimum, you may want to split the
capacitance values into two (half values) and place them at the input and
output instead of just being at the output. if you really want a wideband
model, you will need more lumps.

Hope this will get you going.

Regards,

Istvan Novak
Oracle



On 8/28/2015 3:36 AM, Johan Lans wrote:

Hi
First of all, condolences to everyone who knew Steve Weir. I referenced
his
work in my masters thesis in physics a few years ago.
I'm trying to understand simulation of crosstalk by doing some field
solving of a trace pair using MMTL (the Multilayer Multiconductor
Transmission Line 2-D and 2.5-D electromagnetic modelling tool suite,
http://mmtl.sourceforge.net/). The solver can output an HSpice w-element
model of the signal pair, and I'm trying to replicate the crosstalk levels
reported by the solver by setting up an equivalent circuit in LTSpice.
However, I am not quite sure how to translate all the details into an
equivalent circuit, so if I walk through my thought process doing this,
maybe someone can point if I'm doing anything wrong?
In the end of this email, I'm pasting the solver output from TNT 1.2.2, as
well as the w-element output.
The Spice model is a simple RLGC-model. One for the aggressor (I'll call
the components Ra, Ca and so on)and one for the victim (Rv, Cv ..), with
an
extra capacitor for coupling between the two circuits (Cav). The
inductors
are coupled using a coupling factor. A link to the LTSpice design is here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.asc
Following Eric Bogatins chapter on crosstalk in "Signal and Power
Integrity
Simplified, 2nd ed", I came up with the values like this: From the
w-element file,

La = L0(1,1) = 3.29962e-007 H
Lv = L0(2,2) = 3.29953e-007 H
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.175

Ca = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cv = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cav = -1*C0(2,1) = 1.49773e-011 F

Ra = R0(1,1) = 11.4286 Ohm
Rv = R0(2,2) = 11.4286 Ohm

G0 and Gd is zero, and I omitted Rs , since I'm not really interested in
losses right now.

TNT calculates fare end crosstalk to and near end crosstalk to . I'm not
sure how to translate this to measurements in LTSpice, but I injected a
1V,
100ns, step into the aggressors resistor and measured how much signal was
crosstalked over at the Cav end of the victim circuit (a bit difficult to
explain without schematic, but here's a screen capture from LTSpice:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.png) The
crosstalked signal has an amplitude of about 18mV, which is about -55dB. I
interpret this as being near end crosstalk, since there is no actual
length
in the model. The field solver reports near end crosstalk to be -41dB, but
far end crosstalk to be -57dB.

Am I doing anything right here?


Thanks in advance from
Johan



As reference, the field solver files are here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.xsctn
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.result
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.hspice-w.rlgc




2015 08 28 09:12:31 johan.lans NMMTL_2DLF

File = C:/Program Files (x86)/tnt-1.2.2/examples/xtalk
Number of Signal Lines = 2
Number of Ground Planes = 1
Number of Ground Wires = 0
Coupling Length = 1.00000 meters
Rise Time = 100000.0012 picoseconds
Contour (conductor) segments [cseg] = 10
Ground Plane/Dielectric segments [dseg] = 10
Conductivity RectCond1R1 = 5e+007 siemens/meter
Conductivity RectCond1R0 = 5e+007 siemens/meter
Note: minimum frequency for surface current assumptions is 1655 MHz.
Mutual and Self Electrostatic Induction:
B(Active Signal , Passive Signal) Farads/Meter
B( ::RectCond1R1 , ::RectCond1R1 )= 1.1691868e-010
B( ::RectCond1R1 , ::RectCond1R0 )= -1.6413763e-011
B( ::RectCond1R0 , ::RectCond1R1 )= -1.4977254e-011
B( ::RectCond1R0 , ::RectCond1R0 )= 1.1813248e-010

Mutual and Self Inductance:
L(Active Signal , Passive Signal) Henrys/Meter
L( ::RectCond1R1 , ::RectCond1R1 )= 3.2996223e-007
L( ::RectCond1R1 , ::RectCond1R0 )= 5.7727959e-008
L( ::RectCond1R0 , ::RectCond1R1 )= 5.7747599e-008
L( ::RectCond1R0 , ::RectCond1R0 )= 3.2995263e-007

Asymmetry Ratios:

Asymmetry ratio for inductance matrix:
0.034021% (max), 0.034021% (average)

**********
Asymmetry ratio for electrostatic induction matrix:
8.751856% (max), 8.751856% (average).
(Note values greater than 1% are a probable indication of too few
elements.
Try adjusting CSEG and DSEG attributes.)
**********

Characteristic Impedance (Ohms):
For Signal Line ::RectCond1R1= 53.1239
For Signal Line ::RectCond1R0= 52.8495

Characteristic Impedance Odd/Even (Ohms):
odd= 45.186
even= 62.1082

Effective Dielectric Constant:
For Signal Line ::RectCond1R1= 3.36577
For Signal Line ::RectCond1R0= 3.40061

Propagation Velocity (meters/second):
For Signal Line ::RectCond1R1= 1.6340992e+008
For Signal Line ::RectCond1R0= 1.6257061e+008

Propagation Velocity Odd/Even (meters/second):
odd= 1.65982e+008
even= 1.60201e+008

Propagation Delay (seconds/meter):
For Signal Line ::RectCond1R1= 6.1195795e-009
For Signal Line ::RectCond1R0= 6.1511734e-009

Propagation Delay Odd/Even (seconds/meter):
odd= 6.02475e-009
even= 6.24218e-009

Rdc:
Rdc(Active Signal , Passive Signal) Ohms/Meter
Rdc( ::RectCond1R1 , ::RectCond1R1 )= 1.1428571e+001
Rdc( ::RectCond1R1 , ::RectCond1R0 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R1 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R0 )= 1.1428571e+001

Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )= -1.48130e-003 = -56.58711 dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )= 9.25449e-003 = -40.67295 dB

NOTE: Cross talk results assume there are no reflections.









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Answered byistvan.novak 5 years 18 days
Johan,

There are a few things that you will need to change to make this work.
To get near end and far end crosstalk, you need four ports that you may
want to terminate in its average characteristic impedance: the geometric
mean of even and odd mode impedances). Though you may not be interested
in delay and length, the way how the numbers are supplied, refer to a
particular length, so your circuit will be a four port circuit. You
need to check the field solver, what unit length it assumes. From the L
and C numbers you quote, it may be one meter. The characteristic
impedance from these L and C numbers appears to be close to 50 ohms, so
the Ra and Rv numbers may represent the losses. If you want a lossless
equivalent circuit, you can replace those numbers with zero, but you
have to add the proper termination at all four ports. Finally, this is
a single-lump equivalent circuit, because you have one lumped
capacitance and one lumped inductance for the entire length. As a
minimum, you may want to split the capacitance values into two (half
values) and place them at the input and output instead of just being at
the output. if you really want a wideband model, you will need more lumps.

Hope this will get you going.

Regards,

Istvan Novak
Oracle



On 8/28/2015 3:36 AM, Johan Lans wrote:
Hi
First of all, condolences to everyone who knew Steve Weir. I referenced his
work in my masters thesis in physics a few years ago.
I'm trying to understand simulation of crosstalk by doing some field
solving of a trace pair using MMTL (the Multilayer Multiconductor
Transmission Line 2-D and 2.5-D electromagnetic modelling tool suite,
http://mmtl.sourceforge.net/). The solver can output an HSpice w-element
model of the signal pair, and I'm trying to replicate the crosstalk levels
reported by the solver by setting up an equivalent circuit in LTSpice.
However, I am not quite sure how to translate all the details into an
equivalent circuit, so if I walk through my thought process doing this,
maybe someone can point if I'm doing anything wrong?
In the end of this email, I'm pasting the solver output from TNT 1.2.2, as
well as the w-element output.
The Spice model is a simple RLGC-model. One for the aggressor (I'll call
the components Ra, Ca and so on)and one for the victim (Rv, Cv ..), with an
extra capacitor for coupling between the two circuits (Cav). The inductors
are coupled using a coupling factor. A link to the LTSpice design is here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.asc
Following Eric Bogatins chapter on crosstalk in "Signal and Power Integrity
Simplified, 2nd ed", I came up with the values like this: From the
w-element file,

La = L0(1,1) = 3.29962e-007 H
Lv = L0(2,2) = 3.29953e-007 H
Coupling factor, k, between La and Lv.
k = L0(2,1)/sqrt(L0(1,1)*L0(2,2)) = 0.175

Ca = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cv = C0(2,1) + C0(1,1) = 1.01942e-10 F
Cav = -1*C0(2,1) = 1.49773e-011 F

Ra = R0(1,1) = 11.4286 Ohm
Rv = R0(2,2) = 11.4286 Ohm

G0 and Gd is zero, and I omitted Rs , since I'm not really interested in
losses right now.

TNT calculates fare end crosstalk to and near end crosstalk to . I'm not
sure how to translate this to measurements in LTSpice, but I injected a 1V,
100ns, step into the aggressors resistor and measured how much signal was
crosstalked over at the Cav end of the victim circuit (a bit difficult to
explain without schematic, but here's a screen capture from LTSpice:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.png) The
crosstalked signal has an amplitude of about 18mV, which is about -55dB. I
interpret this as being near end crosstalk, since there is no actual length
in the model. The field solver reports near end crosstalk to be -41dB, but
far end crosstalk to be -57dB.

Am I doing anything right here?


Thanks in advance from
Johan



As reference, the field solver files are here:
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.xsctn
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.result
https://dl.dropboxusercontent.com/u/4404053/xtalk/xtalk.hspice-w.rlgc




2015 08 28 09:12:31 johan.lans NMMTL_2DLF

File = C:/Program Files (x86)/tnt-1.2.2/examples/xtalk
Number of Signal Lines = 2
Number of Ground Planes = 1
Number of Ground Wires = 0
Coupling Length = 1.00000 meters
Rise Time = 100000.0012 picoseconds
Contour (conductor) segments [cseg] = 10
Ground Plane/Dielectric segments [dseg] = 10
Conductivity RectCond1R1 = 5e+007 siemens/meter
Conductivity RectCond1R0 = 5e+007 siemens/meter
Note: minimum frequency for surface current assumptions is 1655 MHz.
Mutual and Self Electrostatic Induction:
B(Active Signal , Passive Signal) Farads/Meter
B( ::RectCond1R1 , ::RectCond1R1 )= 1.1691868e-010
B( ::RectCond1R1 , ::RectCond1R0 )= -1.6413763e-011
B( ::RectCond1R0 , ::RectCond1R1 )= -1.4977254e-011
B( ::RectCond1R0 , ::RectCond1R0 )= 1.1813248e-010

Mutual and Self Inductance:
L(Active Signal , Passive Signal) Henrys/Meter
L( ::RectCond1R1 , ::RectCond1R1 )= 3.2996223e-007
L( ::RectCond1R1 , ::RectCond1R0 )= 5.7727959e-008
L( ::RectCond1R0 , ::RectCond1R1 )= 5.7747599e-008
L( ::RectCond1R0 , ::RectCond1R0 )= 3.2995263e-007

Asymmetry Ratios:

Asymmetry ratio for inductance matrix:
0.034021% (max), 0.034021% (average)

**********
Asymmetry ratio for electrostatic induction matrix:
8.751856% (max), 8.751856% (average).
(Note values greater than 1% are a probable indication of too few
elements.
Try adjusting CSEG and DSEG attributes.)
**********

Characteristic Impedance (Ohms):
For Signal Line ::RectCond1R1= 53.1239
For Signal Line ::RectCond1R0= 52.8495

Characteristic Impedance Odd/Even (Ohms):
odd= 45.186
even= 62.1082

Effective Dielectric Constant:
For Signal Line ::RectCond1R1= 3.36577
For Signal Line ::RectCond1R0= 3.40061

Propagation Velocity (meters/second):
For Signal Line ::RectCond1R1= 1.6340992e+008
For Signal Line ::RectCond1R0= 1.6257061e+008

Propagation Velocity Odd/Even (meters/second):
odd= 1.65982e+008
even= 1.60201e+008

Propagation Delay (seconds/meter):
For Signal Line ::RectCond1R1= 6.1195795e-009
For Signal Line ::RectCond1R0= 6.1511734e-009

Propagation Delay Odd/Even (seconds/meter):
odd= 6.02475e-009
even= 6.24218e-009

Rdc:
Rdc(Active Signal , Passive Signal) Ohms/Meter
Rdc( ::RectCond1R1 , ::RectCond1R1 )= 1.1428571e+001
Rdc( ::RectCond1R1 , ::RectCond1R0 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R1 )= 0.0000000e+000
Rdc( ::RectCond1R0 , ::RectCond1R0 )= 1.1428571e+001

Far-End (Forward) Cross Talk:
FXT(Active Signal, Passive Signal)
FXT( ::RectCond1R1 , ::RectCond1R0 )= -1.48130e-003 = -56.58711 dB

Near-End (Backward) Cross Talk:
BXT(Active Signal, Passive Signal)
BXT( ::RectCond1R1 , ::RectCond1R0 )= 9.25449e-003 = -40.67295 dB

NOTE: Cross talk results assume there are no reflections.









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