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It has been observed that numerical difficulties may arise when the exact synthesis techniques are applied, especially in the vicinity of the center region. The authors investigate the possibility of circumventing these difficulties by starting the synthesis procedure not from the periphery, as is done conventionally, but from the center point instead. Numerical results are presented, and it is shown that the periphery condition, namely, that the projected aperture of the main reflector be circular, is approximated very well by the solution obtained via the synthesis procedure presented here. >

The authors develop a model capable of predicting the effects of mesh electrical contacts on antenna performance by determining the mesh reflection/transmission coefficients. These coefficients can then be used in a diffraction analysis program to determine the reflector's far-field pattern. A generalized method of moment/Floquet expansion technique is used to formulate the problem for an arbitrary mesh cell configuration. Representative numerical results are constructed for contact and no-contact mesh surface models. Results are compared to measured data and good agreement is observed. >

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. >