orthogonal excitation and periodic boundary condition in hfss

Hi all,
I am simulating a transmit array unit cell designed in a paper in hfss and I'm quite new with it. It is said in the paper that the unit cell is excited by two orthogonal and linearly polarized waves in normal direction. Also, it is simulated with HFSS using periodic boundary conditions. How can I apply these two things in hfss?
The unit cell structure contains one glass substrate and two split ring slot metals on both sides of it. I already excited it on two orthogonal faces with 180 degree phase shift and I put the structure in an air box with radiation boundary condition, but my results are so different from paper results. what did I do wrong? what should I do?
Thank you

What's your paper you are simulating?

Hi, I attached it