[SI-LIST] Re: The precision of Ansoft Maxwell 2D
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: zhang_kun@xxxxxxxxxx
- Date: Thu, 22 Jul 2004 12:17:06 -0400
zhangkun 29902 wrote:
>Scott
>
>I use Ansoft Maxwell 2D to simulate the crosstalk between differential pairs
>without ground plane. The EM field should be of TEM mode.
>
>
>
Zhangkun,
There are several possibilities.
First, it is very difficult to measure this sort of structure.
Additional modes are very easy to excite, so be sure that you are not
exciting additional modes. In HFSS, you may have the same problem if
the ports for the differential pairs are close together. If you have
not done so already, your test structure should have the ability to
separate the differential pairs at the port, so that there is no coupling.
Second, you may need to use a much lower error energy in Maxwell 2D in
order to force a higher mesh density. This will give you a much more
accurate result. If you are interested in crosstalk at one particular
frequency, then I would suggest using the impedance and admittance
matrices to create a w-element model, as it will include the effect of
finite field penetration at high frequencies within the conductors.
Third, the computation boundary in Maxwell 2D can also cause significant
errors if the structure you are extracting is placed too close to the
outside bounding box. Keep enlarging you box, until your matrices do
not change significantly, or produce a plot of the electric and magnetic
fields lines to determine if the boundary is interferring with your
solution.
regards,
scott
Scott McMorrow
Teraspeed Consulting Group LLC
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