Help me enter 100ohm feed point impedance to patch antenna using IE3D

Hi to all,
I am presently engaged in design of folded P.A.T.C.H antenna using IE3D. I am constantly referring to the help manual... I feel its well written ,but I did not find any way to enter the feed point impedance of hte antenna .. I guess IE3D assumes it to be 50 ohms, but I am interested in design of slightly higher impedance (say - 100 ohms) .. Could anyone point to how I could od this? It would be great if jian could answer on this..
Thanking all in advance..
Shantanu Bhalerao,
NIT Nagpur,
India.

For infinite gnd and substrate

1. You need to change the connector dia according to requirement.
2. Change feed impedance to 100 in Modua

For finite gnd and substrate just draw the entire feed including inner and outer conductor of the coaxial probe.

Hi, Shantanu:

On IE3D, we adopt 50-ohm normalization in order to make the s-parameters compatible with the Touchstone format from Agilent/EEsof. The transformation is basically:

V = SQRT( Zc1 ) * ( A1+B1) = SQRT( Zc2 ) * ( A2 + B2 )
I = ( A1 - B1 ) / SQRT( ZC1 ) = ( A2 - B2 ) / SQRT( ZC2 )

where A1 and B1 are the incident and reflected waves normalized to Zc1 and A2 and B2 are the incident and reflected waves normalized to Zc2.

Touchstone format can only accept single Zc for all the ports and this single Zc is normally 50-ohms. When we get the generalized s-parameters normalized to port impedance, we have to re-normalized it to the 50-ohms. For academic people, this normalization may means loss of accuracy or causing some confusion. However, this is a must process for industrial people. Think about it. All the measurement equipments are 50-ohm normalized. When you measure other than 50-ohms, you may try to use some converesions and this conversion also involves accuracy issue. Also, think about a transistor. It is not realistic for the vendor to provide the s-parameters of a kind of transistor for every possible Zc you may use. Using the 50-ohm standard makes it much easier in the industry even though we know it may cause some slight degrade in accuracy if we do not use it properly. Regards.