Asymptotic evaluations of near field physical optics integrals for shaped sub-reflectors

Diffraction analysis of the subreflector scattered field near the rim of the main reflector in a high-gain dual-shaped system was found to have singularity problems. A 34-m ground station dual-shaped reflector with a 20-dB subreflector edge taper was considered. The UTD (uniform geometrical theory of diffraction) and slope diffraction field singularities are due to a geometrical optics caustic on the reflection boundary. Physical optics evaluation has been carried out efficiently and accurately using asymptotic techniques for both symmetric and offset asymmetric subreflectors.<>