In this thesis, parametric study and design of Vivaldi antennas and arrays are studied. The parameters of single element antennas and arrays are investigated regarding their effects on the design. The return loss responses and radiation patterns are considered in the parametric study. The results of simulations realized using Ansoft HFSS, a high frequency electromagnetic field simulation program, are shown and discussed. Two different Vivaldi antennas operating in 8.5-10.5 GHz frequency band with return loss responses better than 15 dB are designed based on the results of parametric study. Stripline to slotline transition is used in the feeding section of both antennas. In the same manner, two different 8-element uniform linear arrays operating in 8.5-10.5 GHz with half power beam widths smaller than 12&amp / #730 / and side lobe levels smaller than 13 dB are designed. Binomial and Dolph-Chebyshev feeding techniques are also investigated in order to improve half power beamwidths and side lobe levels of the designed arrays. The designed single element Vivaldi antennas and a linear array of Vivaldi antennas are fabricated. The return loss response and radiation patterns of the fabricated antennas and the array are measured and compared with the simulation results.

An active, broadband antenna module amenable for use in low cost phased arrays is proposed. The module consists of a Vivaldi antenna integrated with a frequency conversion integrated circuit. A method of orthogonally mounting endfire antennas onto an array motherboard is developed using castellated vias. A castellated active isolated Vivaldi antenna package is designed, fabricated, and measured. An 8x1 phased array of castellated, active Vivaldi antenna packages is designed and assembled. Each element has approximately one octave of bandwidth centered in X-band, and each is mounted onto a coplanar waveguide motherboard. Radiation patterns of the array are measured at several frequencies and scan angles.