Role of Theta and Phi for FSS

Hey,

Can anyone tell that why we have to define the angles theta and phi for analyzing
frequency selective surfaces? How both of these angles can effect the performance? tq

Some of my colleagues had done some designs of FSS in HFSS. I think the Theta and Phi are to define the angle of incidence wave. The response of FSS would be different with different incidence angle.

I agree wholeheartedly... the effective wavelength of the current density excited on a planar metal sheet, or FSS, is induced by the projection of the incident field onto the structure. So for larger angles of incidence, the effective current wave vector is smaller than the incident wavelength. This is also why structures begin to diffract at higher angles of incidence as the electrical spacing between them increases, though the physical spacing is unchanged, due to the smaller wavelength of the current excited.

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