This book addresses analysis and design of high gain transmitarray lens antennas which can be used in satellite communication, radar application system, imaging, and medical applications. Different types of transmitarray antennas are proposed. A new design of transmitarray from one dielectric sheet with etchings of different heights is discussed. A single structure multi-focused transmitarray in the near-field (NF) and/or far-field (FF) is designed by using a chess-board arrangement of unit-cell elements. Multi-focused transmitarray antennas for FF/FF, FF/NF, and NF/NF are investigated. Reflectarrays / transmitarrays of a transparent hemispherical dielectric resonator antenna integrated with solar cells for small satellite and clean energy are proposed. Integration between these antennas and solar cells serves as a cover protection for the solar cell from environment which increases the efficiency of solar cells. A design of compact multi-function graphene lens antenna in terahertz (THz) band is also proposed. Tunability of graphene conductivity introduces multi-function characteristics of a single array structure in the THz band.