The millimetre-wave (mmWave) antenna arrays in traditional designs are usually very complicated, bulky and expensive. They suffer compromised radiation efficiency because of high insertion loss caused by the intricate feed networks. In addition, the cross polarization level is degraded, especially for the multibeam antenna arrays. To reduce the complexity and improve the electric characteristics, it is significant to develop mmWave antenna arrays with multi-functionality such as dual polarization, cross polarization suppression, beam switching and power splitting/combining, etc.In this thesis, four designs of sub-mmWave and mmWave dual polarized antenna arrays with low complexity, compact size and good electrical performance are proposed. Firstly, a dual slant polarized cavity-backed slot-coupled patch antenna arrays with modified feed networks is developed. This antenna array features high XPD, simple structure and low profile. Then, a dual polarized 2D multibeam shorted-patch antenna array with high XPD when beams scan to the maximum pointing angles is developed. Differential feed technique is used to design the multibeam antenna array for the first time. The third design is a dual polarized frequency-scanning cross slot antenna array realized on a single laminate. To enable high port isolation and excitation from orthogonal directions, a SIW crossover is proposed. This antenna array shows advantages in terms of low complexity, high XPD, high aperture efficiency and wide beam scanning range. A dual polarized slot-coupled patch antenna array differentially fed by an orthomode transducer is developed in the last design. The feed networks are taken into consideration of designing the subarray antenna. The via-loaded crossover is used to enable structure simplification and triple resonance is excited to improve operation bandwidth. This antenna array features low complexity, high XPD, high radiation efficiency, high gain and high integration.In this thesis, the design methods and synthesis procedures are detailed in order todeliver a comprehensive guide of designing the dual polarized antenna arrays. The design concept and outcomes of these antenna arrays are evaluated in the high frequency fullwave solver. All of the antenna arrays are prototyped and measured for validating the simulations. The measurements are in good agreement with the simulations, evidencing that the proposed antenna arrays have advantages in terms of high XPD, high aperture efficiency, high port isolation, low complexity and low profile. The design concepts depicted in this thesis and the developed antenna arrays could find potential applications in mobile communication systems and satellite communication systems
