Implementing BPF using DGS in AWR

Hello People,
I'm designing a narrow BPF for a center frequency of 1.38 GHz on AWR. I'm trying to suppress the harmonics. I've been able to suppress the harmonics using open stubs in circuit simulation but it's not giving satisfactory results in EM Simulation. Now I'm trying to implement it using DGS. Could anyone help me out please?