Impact of Edge Diffraction in Dual-Polarized Phased Array Antennas

Abstract

An analytical model is proposed to characterize and quantify the effects that diffracted fields have on the performance of phased array antennas. The work involves the combination of diffraction theory techniques and how each can be used to analyze this phenomena with the use of antenna elements as sources. As these antenna elements are placed along a ground plane of relatively large size in terms of λ diffracted fields can perturb the expected cross-polarization radiation performance of the element. As the element is moved along the ground plane and at different relative distances from the edges, depending on the electromagnetic radiation nature of the antenna structure, these edges produce diffracted fields that can affect the performance of the co- as well as the cross-polarized fields of the antenna. This is of great importance when working with highly pure polarized elements for applications that require low cross-polarization. The expansion of an equivalent current model is proposed where the antenna element can be expressed at a distance from the edges and the diffracted fields generated from such edges are calculated from these equivalent currents. Every element position over the ground plane will generate a theoretical equivalent current that would radiate the diffracted fields, which then contribute to the overall array pattern. This work shows a successful implementation of the proposed technique and how this can be combines with finite element method (FEM) analysis in order to predict the radiated fields from different element positions providing an advantage over resource hungry simulations. This proves to be an effective tool by reducing the calculation time substantially for scalable applications where the phased array can be over thousands of elements and extremely difficult to gather resources to produce a predicted pattern.