With the plane wave source and Bloch boundary conditions, I am able to get the reflection and transmission data up to a certain angle, like 30 degrees, where I did the sweep from 0 to 75 degrees. For higher angle values, I am getting the power normalization is not working properly as I am getting reflectivity of more than 1. And with BFAST source and Bloch boundary conditions (BBC), although it is overwritten by itself if FDTD setting, I am getting normalized values after some angle like 30 degrees; the normalization is not happening properly at a lower value of the angle. I am getting more than 1 reflectivity for lower values of angle. So, the problems are the opposite for plane wave source with BBC and BFAST with BBC.

Please suggest something to resolve this problem with an off-normal incident plane wave source in a periodic structure. Thank you.