Tunable frequency selective surfaces and true-time-delay lenses for high-power-microwave (HPM) applications

Phased array antennas and agile antenna apertures can potentially play a significant role in the future wireless system, and benefit several strategic areas such as ultra-fast data rate wireless transmission and economically viable solar power transmissions. Despite the conventional use of phased array antennas in many military sectors such as airborne and ground based radar systems, the complexity of the array structures as well as the excessive cost of phase shifters and T/R modules prohibits the phased arrays from being deployed in many strategic and commercial systems. A significant amount of this thesis is dedicated to providing innovative and interdisciplinary solutions that could potentially enable the widespread use of high-power-capable and affordable phased-array technology in the future wireless systems.;In this thesis, the concept of tunable space-fed microwave lens is proposed as a promising approach of realizing affordable agile antenna apertures. Using this approach, the entire system is expected to have wideband operation, a strong capability of handling high RF power levels, and negligible losses with greatly simplified architecture. The proposed planar microwave lenses are composed of numerous true-time-delay (TTD) units, and are extremely suitable in broadband pulsed applications. A linear tuning technique that dose not rely on solid-state devices is also proposed as a potential way of making these lenses tunable.;Each time-delay unit in the proposed microwave lenses is in the form of one unit cell of an appropriately designed frequency selective surfaces (FSSs). In this thesis, the FSSs of choice are composed of multiple impedance sheets separated from each other by thin dielectrics. It is first demonstrated that these FSSs can be made tunable by using a fluidically tuning technique that dose not rely on solid state devices. The resulting tunable FSSs have a wide tuning range and can maintain linearity in high power applications. Subsequently, the power handling capability of these FSSs are studied extensively, and the guidelines of designing extremely high-power capable FSSs are provided. Finally, the design of true-time-delay microwave lenses composed of these FSSs are demonstrated. In particularly, the time-delay units of these lenses can be composed of bandpass, lowpass and all-dielectric type FSSs, depending on the specific application.