Computation and radiation pattern and synthesis of dual reflector antennas

Fourier Bessel and launching methods for pattern computation of Cassegrainian antenna systems are examined. The problem of computing the reflected and diffracted fields from a subreflector is considered along with the problem of computing the far-field pattern by integrating these currents on the main reflector. Dual reflector synthesis is then examined; attention is given to the problem of transforming, through two reflections by an offset dual reflector system, a given primary feed pattern into a desired aperture field distribution. A numerically rigorous solution of the surface of the offset two-reflector system is developed. This solution, based on geometrical-optics analysis, gives an exact aperture phase distribution and enforces the condition on the aperture amplitude distribution to within some numerical tolerance.