The reflectarray has been considered as a suitable candidate to replace the conventional parabolic reflectors because of its high-gain, low profile, and beam reconfiguration capability. Narrow bandwidth of the reflectarray is the main obstacle for the various uses of the reflectarray. The wide band element with a large phase variation range and a linear phase response is one of the solutions to increase the narrow bandwidth of the reflectarray. Several elements with a large phase range and a linear response have been developed, but their configurations are complex.Simple methods have been investigated in this dissertation to develop wide band elements. A microstrip ring and slot element with a large phase range is introduced and modified for a better linear response. A coupled element with a linear response has been developed. A method is proposed to design a two-layer reflectarray with multi-resonant elements of various sizes for wideband operation. The element dimensions are adjusted by Particle Swarm Optimization routine to achieve the appropriate phase distribution for a predetermined frequency band. In another approach to increase the operation bands, a six-band reflectarray has been developed. As a new application of a reflectarray, a rectifying reflectarray, which is composed of a rectenna and a reflectarray, is introduced in this dissertation. The reflectarray directs RF energy from its aperture to the rectenna located on the feed point of the reflectarray. This configuration eliminates complex feeding networks and design difficulties of the conventional rectenna array. A Double Sided Parallel Strip Line (DSPSL) is adapted for the feeding network of the Archimedean spiral antenna. The DSPSL operate very well to feed the Archimedean spiral antenna over the bandwidth. The research presented in this dissertation suggests useful techniques for wideband reflectarrays, wireless power transmission, and wideband antenna designs.
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