plastic material HFSS

Hi to all. I'm simulating a monopole for an GSM/GPRS/EDGE/UMTS/HSPA application but i have a problem. The monopole is located on a plastic support (thickness=1mm) 3mm over FR4 substrate. (See image for details). Does anyone know which type of material I have to use for plastic support? And does anyone know ho to determinate the effective index used to calculate the length of the monopole?

Thanks

Bye

Francesco

Since you are working on a monopole a very thin dielectric may work well as a support while still remaining transparent to the RF signal.

thanks for your answer, but the problem is that I have to analyze a just manifactured antenna for a GSM/GPRS/EDGE/UMTS modem. I know that the antenna has some problems and I'm tryin' to simulate 'cause I want to make some improvement on. The antenna is located over a plastic support, the there is 3mm of air and then based on a FR4 substrate: how can I reproduce plastic (think PVC) in HFSS material?

thanks

Francesc

look up the dielectric constant for PVC and add that to your model.