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[qcu89]

Hi everyone!
I am looking for solution how to design LTCC filter (CST MVS).
- dimensions required 3x2 mm,
- bandpass from 2.3 to 2.5 GHz
- green tape - dupont 9k7

Main problem is to transform lumped elements to planar capacitors and coils. I can't find solution for that. I'm attaching model from Ansoft.



Do you guys have any info how to transform lumped elements into planar?
Thanks for all advices!

[bigSteve]

For capacitors, why don't you just use parallel plates (conductors separated by a distance, start with C=epsilon*Surface_Area/distance_between_conductors). For inductors, just use wires or meandered loops (increasing the length for more inductance). Simulate your components independently to get the values right and then put it all together and tune it a bit.

[qcu89]

so:

correct me if I'm wrong for capaciotrs.
let's assume that I want capacitor which have 20pF and I'm working on dupont 9k7 (eps=7.1) then the equation for plates dimensions will be:

S=20*d/eps

where S is surface in mm, d is distance between plates (0.127mm).
It gives me surface of ~0.4mm. Am I right?

and another question, is there a equation for planar inductance?

thanks again!