SL900A UHF RFID tag design

Hello everyone,

I am newbie at RFID sector.

As a part of my project work, I wanted to design a RFID tag (SL900A(http://ams.com/eng/Support/Demoboard...L900A-Demo-Kit) in CST.

I tried to design the tag but I am not sure whether my port design is right. After designing the tag I got weird S11.

so, I would like know, how can I design the port and tag here?

thanks