Beam Shaping Of Parabolic Antennas Based On NURBS

With physical optical method (PO) founded on the integration of surface induced current, the applications of non-uniform rational B-spline (NURBS) modeling method using in the electromagnetic computation are discussed. The computation is mainly about radar cross section (RCS) of perfect conductors and radiation patterns of parabolic antennas. Taking considerations of the real-coded genetic algorithm (RGA), beam shapings of array antennas/parabolic antennas are studied.At first, surface modeling by NURBS is studied. The characteristics of the surfaces, such as surface precision, cut amounts, and surface continuity after distortion, are discussed. And advantages of this modeling method are summarized.Then, by the NURBS modeling technology, a cylindrically curved plate, a spherically curved plate, a conesphere, a conical curved plate and a parabolic reflector are modeled. The RCSs of those perfect conductor surfaces with electrically large dimensions, and far field radiation patterns of the parabolic antenna are computed with PO.What's more, RGA, especially the chosen of cost functions, is studied. To test the object functions, optimizations of array antennas are carried out.Finally, through optimizing the parabolic reflector shape with RGA by adjusting the positions of the control points, some expected shaping beams are achieved, such as a flat beam with rotationally symmetric surface, an equilateral triangle beam and a square beam with axially symmetric surface.