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Alejandro
Spain
14 Posts |
 Posted - Jun 26 2014 : 19:53:47
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Hello Enrico,
how are you? I'd want to obtain the capacitance between two coils connected through a via with a dielectric emulating a PCB between them with relative permitivity 4.5.
This is the list file i've used, plus the comments:
C group01_d10.qui 1.000000 0.0 0.0 1.03 + /*First coil*/
C via.qui 1.0 0.0 0.0 -0.035 + /*Via connecting the coils in series*/
C group01_d10.qui 1.000000 0.0 0.0 -0.035 /*Second coil*/
D dielectrico_nxyz10.qui 1.0 4.5 -15 -15 0 50 50 0.5 /*Dielectric*/
I have the following doubt: the <xref> <yref> <zref> defined in the D sentence is inside the dielectric, however, if i remove the - sign the capacitance obtained is higher than without the -; but because the ref point is inside the dielectric, it should have the minus sign at the end of the D sentence, isnīt it?
Regards.
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Enrico
550 Posts |
Posted - Jun 28 2014 : 00:05:14
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From the embedded FasterCap online help:
quote:
Syntax: D <file> <outperm> <inperm> <xoffset> <yoffset> <zoffset> <xref> <yref> <zref> [-]
The 'D' element at the beginning of a line defines a dielectric. The geometry of the dielectric surface is further specified in the file <file>. The dielectric surface is intended as the interface between two regions with relative permettivities <outperm> and <inperm>. The relative permittivities <outperm> and <inperm> can be complex valued, in the format eRe-jeIm, where eRe is the real part of the complex permittivity value, and eIm is the imaginary part. The dielectric can be translated with respect to the coordinates defined in <file> by an offset (xoffset, yoffset, zoffset), thus allowing to reuse the same geometric definitions multiple times. The reference point (xref, yref, zref) and the optional - argument are used to specify which side of the dielectric interface has which permittivity. More specifically, the reference point is assumed to lie on the <outperm> side of all the panels in <file>. The optional - argument indicates that (xref, yref, zref) instead lies on the <inperm> side. The reference point is not translated, i.e. the offset only applies to the elements specified in <file>.
So looks like you inverted the two permittivities. I also note that your via is inside a dielectric medium with permittivity = 1.0, while I think it should be 4.5 from your explanation (but without the geometric definition files it is difficult to say for sure)
Best Regards,
Enrico
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Alejandro
Spain
14 Posts |
Posted - Jun 28 2014 : 19:03:37
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"So looks like you inverted the two permittivities" Do you mean i have inverted them because i haven't used the - sign at the end of D sentence?
Yes, the via is inside the dielectric, i should change that (when i change it the capacitance varies very little); the ref point defined is inside the dielectric but removing the - the capacitance is higher. I don't understand it. The .qui files are long but i could send them if they give some help, its size is less than 500kB.
I also don't know if the discretization is the problem because as i increase it i get "Out of memory".
Regards. |
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Enrico
550 Posts |
Posted - Jul 03 2014 : 01:34:22
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No I mean that, from your input file and according to what explained in the help, the reference point (50, 50, 0.5) appears embedded in a dielectric medium with a constant of 1.0, while I would have expected it to be 4.5.
Best Regards,
Enrico
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Alejandro
Spain
14 Posts |
Posted - Jul 03 2014 : 17:16:30
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Thank you, it's as i thought, but, what i don't understand is that using only "C group01_d10.qui 1.000000 0.0 0.0 1.03" the calculated capacitance is higher than using
"C group01_d10.qui 1.000000 0.0 0.0 1.03
D dielectrico_nxyz10.qui 1.0 4.5 -15 -15 0 50 50 0.5 -".
And also using
"C group01_d10.qui 1.000000 0.0 0.0 1.03 +
C via.qui 1.0 0.0 0.0 -0.035 +
C group01_d10.qui 1.000000 0.0 0.0 -0.035"
the capacitance obtained is higher than
"C group01_d10.qui 1.000000 0.0 0.0 1.03 +
C via.qui 4.5 0.0 0.0 -0.035 +
C group01_d10.qui 1.000000 0.0 0.0 -0.035
D dielectrico_nxyz10.qui 1.0 4.5 -15 -15 0 50 50 0.5 - "
How is it possible that introducing a dielectric with a higher permitivity the capacitance be lower?
Regards. |
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Enrico
550 Posts |
Posted - Jul 04 2014 : 19:05:21
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Please send the full input files (you can send them to my email address or to the standard support email) as w/o the full geometry is difficult to answer you.
Best Regards,
Enrico
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PCB capacitance
