Reflection loss (s11) plot of reflectarray antenna

Hello!
Can any one help me regarding the reflection loss plot of reflect array antenna vs frequency ? How much it Should be at resonant frequency?
plzz plzzzzzzzz Helpp!!!
I will be Thankfull :)

Any good antenna should have S11 high (SWR close to 1:1) for a good radiation efficiency.
It means its impedance is well matched to the transmission line.
Compromising antennas allow S11 to be lower than 20 dB=this means power is reflected back to the line, not radiated.