Reflector for a fixed position radar antenna

Each antenna is composed by a feeding horn, equal for all the antennas of the series, and a specific reflector. The feeding horn is a pyramidal horn with an aperture , that links up to the standard WR12, and a depth of 23.5mm. The latter has been shaped on both E- and H-planes according to the results of an ad hoc design procedure that makes use of the Alternating Projection method and employs a 3D Physical Optics approach. Indeed, an initial shaping of the reflector is defined by using a GO approximation. Then the diffraction error is reduced by applying the following iterative scheme [9]. At each iteration step, the far-field radiation pattern is calculated in the u-v plane by using Physical Optics. Next, the pattern constrains are imposed, namely the radiation pattern is clipped within the admitted ripple level inside the sectorial main lobe region, whereas it is clipped below the admitted side lobe level outside it. Then, a new surface current on the reflector is calculated by applying the inverse Physical Optics radiation integral. The thus obtained surface current is compared to the original surface current and a phase error is defined. It reveals how the reflector shape has to be locally modified at any point, in order to fulfill the radiation pattern constrains. Hence, the control points, which define the reflector shape, are moved accordingly to the phase error indication to reduce it. The process is then repeated until the pattern shape converges to the target one.