Radar ground-clutter shields

Metal shields (or fences) are used to reduce the ground clutter received by a radar. The design of a clutter shield for an L-band radar employing a 60-foot parabolic reflector with Cassegrain geometry is verified by scale-model measurements at K_{a} -band. It is shown that a 100-foot fence at a distance of 500 feet from the radar will give a nominal one-way clutter reduction of 20 db. More than 10 db additional clutter reduction was achieved by cutting rectangular slots in the top edge of the fence. However, these and other periodic structures are subject to "resonances" related to grating lobes, as was shown experimentally and theoretically by the principle of stationary phase. A proposed nonperiodic edge treatment is expected to be free of this troublesome effect.