complex dielectric constant

Hello,
I'm using CST Microwave and I would like to define a layer with a complex dielectric constant and I don't know how to proceed. Could you help me?
Thanks

Hello Charlyy,

A complex permittivity means there is some losses in the dielectric. So you can put a losses by increasing the tan(delta) in the material properties.

Hope I help you

regards

piboo

hi

yes i agree with piboo . complex permitivity means you have loses in substrate.
inorder to model losses you can either mention loss tangent or conductivity

i hope it helps

regards

For your problem, you need to write epsilon and mu in terms of tangent delta electric and magnetic. (For dielectric and magnetic losses.) You need to also enter conductivity losses, if present. Just look at the freq dependent formulas for complex eps and mu, in an advanced EM book...

Off topic:

When I was working with metamaterials in the past, I tried to run a hypothetical problem in CST, which would include negative epsilon/mu. As it turned out, CST did not allow eps<1 and mu<1. Then I switched to HFSS.

This was in CST 5.0, i guess. Is it still the same for the newest CST version? Just wondered...

At the 2006 version of CST you can enter negatives number, but I don't know if the simulation works correctly with this.

Just a question about complex permittivy and tan(delta):

In some publications you can find:
EpsilonR=Epislon'+j*Epsilon"

which definition are you using to convert Epsilon" to tan(delta) ?

Thanks

To piboo,

I think you can obtain Epsilon" by using Epsilon'*tan(delta).

if you are using e^jwt time dependence (most solvers use this), then:

EpsilonR=Epislon'-j*Epsilon"

where tan_delta_e (electric) = Epsilon"/Epislon'

Thank you all,

I found it later but I forget to post it.

regards

piboo