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Rain

2 Posts

Posted - Nov 20 2012 : 18:52:59

Hi,

I tried to simulate a PCB printed inductor, i made a C program to generate a parametric one

This is an inductor with 10 turn, W = 0.4mm S= 0.4mm and 35um of track height

.unit MM

.default nwinc=8 nhinc=1 sigma=5.8e4

N1 x= 0.0000 y= 0.0000 z= 0.0000
N2 x= 1.6000 y= 0.0000 z= 0.0000
N3 x= 1.6000 y= -2.4000 z= 0.0000
N4 x= -0.8000 y= -2.4000 z= 0.0000
N5 x= -0.8000 y= 0.8000 z= 0.0000
N6 x= 2.4000 y= 0.8000 z= 0.0000
N7 x= 2.4000 y= -3.2000 z= 0.0000
N8 x= -1.6000 y= -3.2000 z= 0.0000
N9 x= -1.6000 y= 1.6000 z= 0.0000
N10 x= 3.2000 y= 1.6000 z= 0.0000
N11 x= 3.2000 y= -4.0000 z= 0.0000
N12 x= -2.4000 y= -4.0000 z= 0.0000
N13 x= -2.4000 y= 2.4000 z= 0.0000
N14 x= 4.0000 y= 2.4000 z= 0.0000
N15 x= 4.0000 y= -4.8000 z= 0.0000
N16 x= -3.2000 y= -4.8000 z= 0.0000
N17 x= -3.2000 y= 3.2000 z= 0.0000
N18 x= 4.8000 y= 3.2000 z= 0.0000
N19 x= 4.8000 y= -5.6000 z= 0.0000
N20 x= -4.0000 y= -5.6000 z= 0.0000
N21 x= -4.0000 y= 4.0000 z= 0.0000
N22 x= 5.6000 y= 4.0000 z= 0.0000
N23 x= 5.6000 y= -6.4000 z= 0.0000
N24 x= -4.8000 y= -6.4000 z= 0.0000
N25 x= -4.8000 y= 4.8000 z= 0.0000
N26 x= 6.4000 y= 4.8000 z= 0.0000
N27 x= 6.4000 y= -7.2000 z= 0.0000
N28 x= -5.6000 y= -7.2000 z= 0.0000
N29 x= -5.6000 y= 5.6000 z= 0.0000
N30 x= 7.2000 y= 5.6000 z= 0.0000
N31 x= 7.2000 y= -8.0000 z= 0.0000
N32 x= -6.4000 y= -8.0000 z= 0.0000
N33 x= -6.4000 y= 6.4000 z= 0.0000
N34 x= 8.0000 y= 6.4000 z= 0.0000
N35 x= 8.0000 y= -8.8000 z= 0.0000
N36 x= -7.2000 y= -8.8000 z= 0.0000
N37 x= -7.2000 y= 7.2000 z= 0.0000
N38 x= 8.8000 y= 7.2000 z= 0.0000
N39 x= 8.8000 y= -9.6000 z= 0.0000
N40 x= -8.0000 y= -9.6000 z= 0.0000
N41 x= -8.0000 y= 8.0000 z= 0.0000
E1 N1 N2 w= 0.400000 h= 0.035
E2 N2 N3 w= 0.400000 h= 0.035
E3 N3 N4 w= 0.400000 h= 0.035
E4 N4 N5 w= 0.400000 h= 0.035
E5 N5 N6 w= 0.400000 h= 0.035
E6 N6 N7 w= 0.400000 h= 0.035
E7 N7 N8 w= 0.400000 h= 0.035
E8 N8 N9 w= 0.400000 h= 0.035
E9 N9 N10 w= 0.400000 h= 0.035
E10 N10 N11 w= 0.400000 h= 0.035
E11 N11 N12 w= 0.400000 h= 0.035
E12 N12 N13 w= 0.400000 h= 0.035
E13 N13 N14 w= 0.400000 h= 0.035
E14 N14 N15 w= 0.400000 h= 0.035
E15 N15 N16 w= 0.400000 h= 0.035
E16 N16 N17 w= 0.400000 h= 0.035
E17 N17 N18 w= 0.400000 h= 0.035
E18 N18 N19 w= 0.400000 h= 0.035
E19 N19 N20 w= 0.400000 h= 0.035
E20 N20 N21 w= 0.400000 h= 0.035
E21 N21 N22 w= 0.400000 h= 0.035
E22 N22 N23 w= 0.400000 h= 0.035
E23 N23 N24 w= 0.400000 h= 0.035
E24 N24 N25 w= 0.400000 h= 0.035
E25 N25 N26 w= 0.400000 h= 0.035
E26 N26 N27 w= 0.400000 h= 0.035
E27 N27 N28 w= 0.400000 h= 0.035
E28 N28 N29 w= 0.400000 h= 0.035
E29 N29 N30 w= 0.400000 h= 0.035
E30 N30 N31 w= 0.400000 h= 0.035
E31 N31 N32 w= 0.400000 h= 0.035
E32 N32 N33 w= 0.400000 h= 0.035
E33 N33 N34 w= 0.400000 h= 0.035
E34 N34 N35 w= 0.400000 h= 0.035
E35 N35 N36 w= 0.400000 h= 0.035
E36 N36 N37 w= 0.400000 h= 0.035
E37 N37 N38 w= 0.400000 h= 0.035
E38 N38 N39 w= 0.400000 h= 0.035
E39 N39 N40 w= 0.400000 h= 0.035
E40 N40 N41 w= 0.400000 h= 0.035
.external N1 N41

.freq fmin=1e4 fmax=1e8 ndec=1

.end

The software return in output:
0.710135+0.000900107j at 10KHz
which yeld to about 710mOHM of series resistence and 900uH of inductance

The inductance of this coil given by the approximation is on the order of 780nH and 400mOHM

The ESR is OK, but the inductance is 3 order of magnitude off, am i interpreting the data in a wrong way? Is my spiral ill described?

Thanks

Rain

2 Posts

Posted - Nov 21 2012 : 09:55:24

after some troubleshooting i found what the problem was:

the first line of the .inp file is ignored, so in my case the .unit statement was dropped and the program calculated with it's default measure unit (meter perhabs?)

I put a comment line in the first row and simulated the code again, now i get

0.472909+9.10647e-007j at 10KHz

470mOHM of series resistence and 910nH of inductance is the right order of magnitude for this inductor

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