Complex ray analysis of radiation from large apertures with tapered illumination

An attempt is made to model the initial distribution of radiation emitted by an antenna feed in terms of a building-block approach. Attention is given to both near and far field calculations for large apertures with tapered illumination. Generalized one-dimensional tapered profiles expressed in terms of the wavenumber and the aperture coordinate are used to handle profiles ranging from gaussian to rectangular. The analysis covers complex ray tracing from the aperture plane to the observer. The inclusion of all relevant rays is assured by a saddle point analysis of the exact field integral. The ray tracing procedure is demonstrated to be effective without reference to an aperture integral. Several field radiation patterns are calculated as examples.