<font color="red"><u>'''It is very important to keep in mind that only in the case of normal incidence does EM.Cube compute the reflection and transmission coefficients over the entire specified bandwidth of the project.'''</u></font> At oblique incidences when θ > 0, the computed R/T coefficients after the discrete Fourier transformation are valid only at the center frequency of the project for the given value of the incident θ<sub>0</sub> angle. In other words, the computed R/T coefficients at all the other frequencies away from the center frequency correspond to different values of the incident θ angle. As a result, EM.Cube only saves the reflection and transmission coefficients at the center frequency into the output data files "reflection_coefficient.CPX" and "transmission_coefficient.CPX".
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Figure 1: Magnitude and phase of the complex reflection and transmission coefficients of a periodic surface plotted vs. frequency.