dB s(1,1) plots in an array in HFSS

[noorulain069]

I have simulated a linear antenna array in hfss.
the return loss plots for 1 into 2 array , 1 into 4 array, 1 into 8 , 1 into 16 and 1 into 32 array are not the same
the 2 elements array is resonant at 5.08 GHz, 4 elements array again at 5.08 GHz , 8 elements array at 5.2 GHz . 16 elements array at 5.6 GHz and 32 elements array at 6.2 GHz
this is resulting return loss even greater than -5 dB at 5 GHz
i want the response to be at 5 GHz,atleast -20 dB return loss at 5 GHz
the plot i am talking about has db S(1,1) on y axis and frequency on x axis
can somebody tell me that what could be the reason and solution for this?

 

[PlanarMetamaterials]

The reason is that there is coupling between the array elements. One element by itself will not behave in the same way when it is affected by its neighbors.

You can reduce the coupling by spacing out the elements, or using coupling mitigation techniques such as DGSs or EBGs.