Dielectric constant calculation

[cyai]

Hi, everybody

We know an antenna built-in a plastic housing, the resonant frequency will be shifted to lower band. For building simulation model, we shall create a housing mode into the antenna model. My question is, if we take a housing, but we don't know the dielectric constant of this housing, could you tell me how to calculate/measure the dielectric constant for building the accuracy model.

Thanks in advance.

 

[vfone]

**broken link removed**

 

[VSWR]

A solution would be to model the antenna and it's plastic housing in CST MWS, Ansoft HFSS or similar program. Start by assigning dielectric constant to 1.0 of the plastic housing. Then increase plastic housing dielectric constant in steps of e g 0.2 and re-run the simulation between each step. When you notice a change in antenna resonance frequency being the same as you have measured, you have obtained the plastic housing dielectric constant with an accuracy of about 0.2, the step size.

If desired, you can at this point continue simulations using a smaller stepsize e g 0.02 or so to get a better accuracy of the dielectric constant.

If you know what kind of plastic material used in the plastic housing, you can save simulation time by assigning the start value more close to the final result.

There are many tables of plastic dielectric properties on the Internet. Here are a few:

www.clippercontrols.com/info/dielectric_constants.html
www.machinist-materials.com/comparison_table_for_plastics.htm
www.asiinstruments.com/technical/Dielectric Constants.htm

 

[cyai]

I forgot to adding another parameter, how about "loss tangent"?

thanks in advance.

 

[Lupin]

Sorry guys, I have to desing a microstrip antennna by HFSS and maye u can help me... The HFSS help doesn't work.. I don't know why...

Please can u upload tutorial or training stuff in order to follow a step by step procedure to implement the structure and to run the simulation ? For example (how can I create a fix? a layer structure?a probe connecting the ground plane and the fix? how can I set the mesh?...? ) .

Thanks for your cooperation.

Lupin