microstrip rectangular antenna-S11parameter

By using ADS momentum i have measure the input return lose S11 of a microstrip rectangular antenna as suggest by the momemtum example.the following is a list of question i dont understand.could anyone help.
1)how does this S11parameter affect the characteristic of antenna?y do we need to measure and what is the best value we should optimised.
2)how do i optimised the antenna geometry to 50ohm as in the optimisation goal there is not impedance can be selected,only S-parameter.i am using inset feed.

One factor that affects the efficiency of the antenna is the power reflected at the antenna-transmission line junction. You want the return loss to be nearly zero. So optimize for S11 being the most negative (in dB) value you can get. Or in real numbers, closest to zero.

Dear sir,

if i got S11 around 5 or 7 dB. what is the fault in my system? how can i define waveport size ?
thank you.

Hi pkg,

5-7dB means you don't have good matching and need to change your feed location. For waveport size, I think you already got a reply to the message you've sent earlier.