Efficient numerical techniques for the electromagnetic scattering from electrically large objects.

In this thesis efficient and innovative techniques to solve electrically large radiation and scattering problems involving arbitrarily shaped tridimensional objects are shown. We started with electromagnetic principles, to supply the theoretical basis for the numerical methods presented. Then, the Method of Moment (MoM) that allows us to analyze perfect and imperfect conductors by means of a numerical procedure is shown. Next, to overcome the problems associated with MoM, the Characteristic Basis Function Method (CBFM) has been described. Finally, two new improvements of CBFM have been proposed: the Ultra wide band CBFs (UCBFS) and the technique to solve radiating problem of conformal aperture antenna on PEC structure. The UCBFs are the characteristic basis functions (CBFs) that are derived for the highest frequency in the range of interest. These CBFs, once generated, also capture the electromagnetic behavior of the lower frequencies as well. The use of these bases enables us to solve the scattering for any frequency sample in the band without going through the time-consuming process to generate the CBFs anew. To solve radiating problems involving structure with apertures (slots), we can replace the slots with PEC and by applying the CBFM to the entire structure, using appropriate magnetic current densities as sources, together Plane Wave Spectrum (PWS) excitations. The magnetic current densities are obtained by solving a local problem. The numerical results are shown in the thesis to validate the accuracy and the time efficiency of these new techniques.