Receiving cross section of an active waveguide array element

An accurate method to predict the receiving cross section or effective area of a waveguide element immersed in an active array environment is presented. Components of the coax transition to the T/R module and the aperture matching network as well as the waveguide-to-free space junction are represented by their generalized scattering matrices. These matrices are combined to yield an overall S-matrix characterization of the element. Both in-band and out-of-band response of the element can be predicted by this procedure. It is found that just using the physical element aperture to represent the effective receiving area is rather inadequate.