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 Results in FH2 differ from analytical/Q3D results.		  New Topic  Reply to Topic
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somikoda

1 Posts
Posted - Apr 17 2011 :  17:10:46  Show Profile  Reply with Quote
Hello!

When I'm calculating the inductance of a rectangular PCB-strand in FastHenry2, the inductance result differ with a factor 1000 compared with analytical/Q3D results. According to various books, the partial inductance of a PCB-strand is about 500nH/m which indicates that the calculated inductance results from FH2 is wrong. Can anyone shed some light over this matter?

The dimensions of the strip are: length=30mm, width=5, thickness=0.018.

FastHenry2: 17615.1nH (@1GHz)
.Units MM
.Default sigma=5.8e4
N1 x=0.1 y=0 z=0
N2 x=0.1 y=0 z=30
E1 N1 N2 w=5 h=0.018 nhinc=5 nwinc=7
.external N1 N2
.freq fmin=1e6 fmax=100e9 ndec=1
.end

Analytical: 18.1nH L = (0.0002*l)*(log((2*l)/(w+t))+0.5+(0.2235*((w+t)/l)))

Q3D: 17.6nH (@1GHz)

Regards
Somikoda

Enrico

550 Posts
Posted - Sep 07 2011 :  23:15:34  Show Profile  Reply with Quote
I'm not sure about your result, running your input file into FastHenry2 gives:


Freq = 1e+009
Row 0: 0.0332692+1.76151e-008j

Meaning 17.6nH @ 1GHz

Best Regards,
Enrico
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Mathias

1 Posts
Posted - Nov 02 2011 :  15:20:33  Show Profile  Reply with Quote
I had the same problem.
The reason was the first line. your first line contains
.Units MM
FastHenry ignors always the first line. So it uses the unit Mils.
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