FreeLists / si-list / [SI-LIST] Re: Finding the impedance of a PCB trace

[Paul Levin <levinpa@xxxxxxxxxxxxx>]

Dear All,

At 1 GHz, the LINPAR field solver (available from Artech House) gives
48.08 ohms.

Doug Brooks wrote:

>As an added reference, the new Polar Quicksolver gives Zo for these 
>dimensions as 47.38 Ohms
>
>The new UltraCAD differential calculator (single ended calculations are 
>free) does not allow a value for H less than 4 mils, BUT, you can scale 
>everything up by a factor of two (check this out with the Polar calculator, 
>you get the same result) and when you do that the UltraCAD calculator gives 
>a value for Zo of 48.5 Ohms. The new UltraCAD calculator will also do 
>differential calculations, but a license is required.
>
>Doug Brooks
>
>
>At 02:28 PM 4/29/2005, Graham Davies wrote:
>  
>
>>This is, of course, related to my search for a good 6-layer stackup.
>>
>>What is the impedance of a PCB trace (microstrip) with the following
>>parameters:
>>Width ......................... 6.00 mil
>>Height above return plane ..... 3.20 mil
>>Thickness ..................... 1.35 mil (1 ounce copper)
>>Dielectric rel. permittivity .. 4.2
>>
>>These are the answers I get from various tools:
>>
>>41... ohms (http://www.icd.com.au/)
>>41.69 ohms (http://www.emclab.umr.edu/pcbtlc/microstrip.html)
>>41.69 ohms (TraceSim version 1.0.0)
>>41.69 ohms (http://www.technick.net/public/code/cp_dpage.php?
>>aiocp_dp=util_pcb_imp_calculator)
>>41.7 .ohms (http://www.sunmantechnology.com/resources/cal_cat00.shtml)
>>46.14 ohms (ZTOOL Impedance Calculator V1.2)
>>47.31 ohms (http://www.rogers-corp.com/mwu/mwi_java/mwij_vp.html)
>>50.89 ohms (http://www.csgnetwork.com/boardrunimpcalc.html)
>>51.27 ohms (TxLine version 1.1)
>>
>>Does anyone have an idea as to why these calculators give results
>>that vary by 20% and which are more reliable?
>>
>>Graham.
>>    
>>
>
>
>------------------------------------------------------------------
>  
>

-- 
Paul A. Levin
Senior Principal Engineer
Xyratex, Manhattan Beach
(310) 372-7352 - home & office
(310) 291-8199 - cell



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