[SI-LIST] Re: The precision of Ansoft Maxwell 2D

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
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
(503) 750-6481 Cellular
http://www.teraspeed.com

Teraspeed is the registered service mark of 
Teraspeed Consulting Group LLC



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