Synthetic aperture functions for arrays of stepped horns

For studying the internal part of the array feeding structure the generalized admittance matrix (GAM) method seems to offer advantages in terms of effectiveness and accuracy, especially when the feeding structure, no matter how complex, can be partitioned into rectangular prisms. When applied to studying the interactions between elements of an array, the GAM algorithm has to be joined with a the method of moment (MoM) in the free space region, that uses the modes of a rectangular waveguide as basis functions. However, the analysis becomes computationally prohibitive both for dynamic memory and CPU time. In order to reduce the computational complexity, the effort should be substantially concentrated on the reduction of the number of unknowns. In this paper is presented a criteria to compress the solving matrix, which is based on synthetic aperture functions (SAP) expansion of the electric field on each array aperture.