Transmission characteristics of inclined wire gratings

Small diameter parallel wires were imbedded in thin plastic sheets and located closely before an antenna dish receiving plane wave
X
band energy. Polarization was parallel to the wires, and the grating interval was varied between a fifth-wavelength and a whole wavelength for different panels. Received intensity was measured for varied grating tilt angles about an axis lying parallel to the wires and near the center of each panel. Sharp and intense transmission dips were observed for tilt angles at which the parasitic reradiation maxima lay in or near the end-fire direction. The shapes and angular positions of the transmission vs tilt angle curves are approximated by a tentative theory which assumes that the input impedance of the grating is independent of tilt angle and that the apparently absorbed power is proportional to the areas under plots of antenna array patterns. A more precise theory which includes the effect of varying input impedance was required to predict approximate amplitudes as well as sharp transmission dips of smaller magnitude.