Antenna design via current control of antenna currents using theory of Characteristic Modes

An approach for designing antennas using the concept of current control and reactive loading is presented. This scheme is based on a modal analysis referred to as Characteristic Modes (CM) which is used to obtain physical insight about the antenna´s behavior and to modify/improve the antenna´s currents to achieve the desired goals. The scheme could be applied to obtain wideband impedance and radiation pattern behavior; however, the reactive loads may exhibit a non-foster behavior which requires active devices. If the wideband condition is relaxed, the technique can be applied to design multiband antennas for various applications where the loads can be foster (lumped elements). The technique was applied to a Universal Serial Bus (USB) and Radio Frequency Identification (RFID) antennas and yielded a much improved antenna performance.