antenna array S11 problem

[wizard_wiz]

I have designed a waveguide 1:16 power divider with s11 <-30dB in required band i.e 13.75-14.5 GHz. in the same band I have designed a dual polarized square horn antenna with s11<-30db. however when I simulate the power divider and antenna array together my s11 drops from -30dB to -15dB. I cant figure out the reason for drop in s11. the waveguide dimensions for power divider are same as input of waveguide. Need some urgent help.

Thanks in advance.

 

[PlanarMetamaterials]

It sounds like a convergence issue, are you adequately meshing all three simulations?

It could also be the case that there is higher than anticipated coupling between the horns which would de-tune the return loss -- can you plot the fields between them and observe coupling?

 

[wizard_wiz]

It sounds like a convergence issue, are you adequately meshing all three simulations?

It could also be the case that there is higher than anticipated coupling between the horns which would de-tune the return loss -- can you plot the fields between them and observe coupling?

The meshing is good, In CST it is 10 per wavelength. for coupling I simulated the 2 horns separately with same array separation and S12 was better than 55dB.

I dont know how to plot fields between 2 antennas?