High frequency Green´s function for tapered planar arrays

The array Green\´s function (AGF) is the basic building block for the full-wave analysis of planar phased array antennas. Its representation in terms of element-by-element summation over the individual dipole radiations can be replaced by a more efficient global representation constructed via Poisson summation. The resulting Poisson-transformed integrals can be interpreted as the radiation from continuous equivalent Floquet wave (FW)-matched source distributions extending over the array aperture. Applying high-frequency asymptotics to each FW-matched array aperture casts the AGF in the format of a generalized geometrical theory of diffraction (GTD) which includes conical wavefront edge diffracted rays as well as spherical wavefront vertex diffracted rays. In this paper, the results which are valid for equiamplitude excitation, are extended to accommodate tapered illumination, which also includes dipole amplitudes tending to zero at the edges. This extension is carried out by a direct Poisson-transformed asymptotic evaluation of the strip-array GF, with the inclusion of asymptotically subdominant "slope" diffracted fields, in addition to the dominant diffracted fields for appreciable edge illumination.