Complete theoretical pattern of a Cassegrain antenna with experimental check of validity

The A-type, B-type and primary-feed diffractions are treated by the theory of rays. The uniform asymptotic theory of electromagnetic diffraction was used for one set of rays in order to suppress the divergence on the shadow boundaries and to avoid discontinuities which occur when the incident field varies rapidly in the vicinity of the diffracting element. Another set of rays was dealt with by the geometric theory of diffraction, since they are not affected by divergence problems. Finally, the equivalent currents method was employed to calculate the field diffracted by the antenna struts in order to consider incident field variations along their length.