Large phased array antennas are widely used in many military and commercial applications. The analysis of large arrays containing many antenna or frequency-selective (FSS) surface elements is inefficient or intractable when brute force numerical methods are used. For the efficient analysis of such structures hybrid methods (analytic and numerical, numerical and numerical) can be used. In this thesis, a hybrid method combining the uniform geometrical theory of diffraction (UTD) and the moment method (MoM) used for the analysis of large, finite arrays is modified for the efficient yet accurate analysis of large printed dipole arrays. In the present hybrid UTD-MoM approach, the number of unknowns to be solved is drastically reduced as compared to the conventional MoM approach, which provides a great efficiency on the computational cost. This extreme reduction in the number of MoM unknowns is carried out by introducing a few UTD-ray type global basis functions for the unknown array element currents. In this study, this hybrid UTD-MoM method is applied to the analysis of a finite, planar periodic array of printed dipoles on a grounded dielectric substrate. The efficiency and accuracy of this hybrid method are demonstrated with some numerical results.

Broadband scanning arrays require small element spacing over a broad frequency band to achieve the desired scan capabilities. Previous research has concentrated on the development of small broadband elements to meet the demands of broadband arrays. However, mutual coupling between elements in a tightly spaced array can change the operating frequency and bandwidth from that of the single isolated element. Several research efforts have focused on minimizing the mutual coupling to maintain the frequency response of the single isolated element. This dissertation focuses on using the strong coupling between Foursquare antennas to obtain the broadband frequency response while maintaining a small element spacing. The isolated Foursquare antenna was modeled using an in-house FDTD code. The modeled current distribution over the frequency band of operation revealed how the antenna achieved a broadband frequency response. Because of this understanding of the single element, the downward shift in the frequency response of the Foursquare antenna in a fully active array could be anticipated. Furthermore, the infinite array models of the Foursquare revealed an increase in bandwidth. Both are desirable characteristics for a broadband scanning array. Therefore, through this research using the Foursquare element, it has been shown that the strong mutual coupling in a tightly spaced array can have advantages if initially taken into consideration when designing the array. / Ph. D.