Experimental investigation of diffraction gratings for millimeter/submillimeter-wave instruments

To better understand the behavior of frequency-selective waveguide gratings at microwave frequencies, measurements have been performed on two periodic arrays of dielectric gratings in the frequency range of 8-12 GHz. This paper briefly describes the measurement results from the electromagnetic wave diffracting from the gratings into the forward and backward waves. The results presented in this paper are compared with the theoretical results of a plane wave case, indicating a strong agreement between the measured data and the theory in the case of the transmission. However, the spherical nature of the incident wave on the gratings exhibits some effects on the results. These effects could be due to the phase differences between the successive periods away from the center of the grating, introducing additional diffraction orders.