Re: [SI-LIST] : Question on transmission line simulation by HP ADS /Momentum

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From: Nianci Wang (nwang@amcc.com)
Date: Fri Apr 27 2001 - 16:21:18 PDT


Hi Ozgur,

Thank you for replying my question.
I understand Momentum does not model metal thickness. When I did in simulation,
I actually draw one metal layer and copy it to another metal layer. Between
these two metal layers, I defined a substrate like air and connected the two
metal layers by via. This is suggested by Momentum manual for modeling finite
metal thickness transmission line.

You are right, for zero thickness, two simulation results match very well.

Best Regards
Nianci

Ozgur Misman wrote:

> Hi Nianci,
>
> We faced a similar problem before. I would say that line cal is more
> accurate then momentum for lossy characteristic impexdance. Momentum does
> not model metal thickness. I think the upcoming version will. The
> impedance you get using line cal is lossy characteristic impedance and that
> matches very well with some state of the art 2-D field solver solutions. My
> guess is you should be ok with momentum if lossles cjharacteristic
> impedance sqrt (L/C) is what you are looking for. For lossy, I would go by
> Line Cal.
> Again, this is purely based on my personal experience and I haven't
> verified it with measurement but used a 2-D solver for comparisons.
>
> Best Regards,
> Ozgur Misman
> Amkor Technology, INC
> Sr. Engineer
>
> "Nianci Wang" <nwang@amcc.com>@silab.eng.sun.com on 04/27/2001 01:24:25 PM
>
> Please respond to "Nianci Wang" <nwang@amcc.com>
>
> Sent by: owner-si-list@silab.eng.sun.com
>
> To: "'si-list@silab.eng.sun.com'" <si-list@silab.eng.sun.com>
> cc:
>
> Subject: [SI-LIST] : Question on transmission line simulation by HP ADS
> /Momentum
>
> Hi,
>
> I have a question on simulating finite metal thickness transmission line by
> using HP ADS Line Calc and Momentum.
>
> Basically I did simulation by using both line Calc and Momentum for several
> different structures, I found that Momentum always give me a higher
> characteristic impedance than that of Line Calc. The thicker the metal is,
> the
> larger the difference between two simulation results. I did talk with HP
> ADS
> help line and got the answer was that Momentum gave more accurate
> simulation
> results. I wonder if any one did the simulation by each line Calc or
> Momentum
> and compared the result with that of the measurement.
>
> Thank you
>
> Nianci
>
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