DFT-UTD based MoM approach for an efficient analysis of scattering from large, finite arrays in the vicinity of scattering objects

This paper presents an efficient hybrid method for analyzing scattering/radiation from electrically large arrays in the vicinity of nearby obstacles. Electrically large arrays are widely used in several applications such as radars, remote sensing systems, and modern communication systems. In general, these arrays radiate in the presence of nearby obstacles, such as an array on a mast. The proposed approach is based on the combination of a ray-field representation of the field radiated by electrically large arrays and a DFT (Discrete Fourier Transform) representation of nonuniform array current distribution. Realistic array current distributions are nonuniform even if the array is excited uniformly due to coupling among the array elements and coupling between array and scattering objects. DFT employment for expressing nonuniform array current distribution is a robust approach, since, for practical array current distributions most of the DFT coefficients are close to zero, except for a few significant terms. When DFT expansion of array currents is substituted in the field expression, it can be observed that the field of nonuniform arrays can be represented as a sum of fields of linear arrays with uniform current distribution. Then, ray description of the field, which is obtained from UTD (Uniform Theory of Diffraction) analysis, for uniform linear array can be employed for each DFT term. To accelerate the calculation of coupling between the array and the scattered object, a few UTD rays emerging from the specific points of the array are used. In the following sections, problem geometry is defined and formulation is given. Furthermore, preliminary numerical results in the form of array current distributions and near field patterns are given to discuss accuracy and efficiency of the proposed method. © 2010 IEEE.