Ideas for open feed of a polygon microstrip?

[Hanh Le]

Dear all

I am trying many open feed length to see effect of it onto S11 and S21. S11 supposed to be smaller than S21 to see no reflection but only transmission. However, all I can get is reversed. Please I need your ideas
Attatched is my feko simulation picture. I cannot attach my feko simulation

 

[sv1437]

Can you attach the frequency response (S11 and S21) for this structure?

 

[Hanh Le]

er = 2.35
freq = 15GHz
open feed width = 1cm
open feed length = 12cm
S11 = -2.5dB
S21 = -12.65 dB
The input has the width of 50 ohm microstrip

This is the best I could achieve

 

[Hanh Le]

The way I put ports is incorrect, I changed to microstrip ports instead of edge port and onto an infinite plane. It works