help me design antenna

Hello.

I am designing a Printed Microstrip Dipole Antenna with the specifications as follows.
1. The antenna is printed on a 1mm thick FR-4 ("r= 4:4) substrate.
2. On the front side, the length of the dipole radiator is lamda/4
3. Frequency: 2.45GHz
This is antenna I designed
But after I put the antenna up to reflect the changed parameters S11
Specifically S11> -10dB.
But the gain is greatly reduced which I know is when I put the antenna up to reflect the gian increased and S11 also not affected
I hope everyone helps to put the antenna up to the problem with
expect people to help



up up up.help me!