Minimized Antenna Based On Composite Right/Left-handed Structures

With the rapid development of the mobile communication, new requirement of the miniaturization of the mobile device is proposed. As a very important part of mobile device, the miniaturization of antenna is of great importance. The conventional microstrip antennas are widely used in communication systems due to the small sizes, low profiles and convenience to be integrated with devices. However, the size of conventional microstrip antennas is relatively in low-frequency band. Although the conventional miniaturization technologies for the microstrip antennas are able to work, they are not quite effective and difficult to learn. So we need new methods to implement the miniaturization of the antenna. In this thesis the composite right/left-handed (CRLH) transmission line (TL) structure is employed for designing the minimized antennas. A novel zeroth-order resonator antenna (ZORA) is designed by using novel CRLH TL structure and modified ground structure, showing higher compactness, enhanced efficiency and bandwidth. The ZORA and improved ZORA are fabricated and measured. In addition, a novel ZORA which is easy to be fabricated is proposed for reducing the manufacture difficulty.The main work and creative points of this thesis can be summarized as follows:1. The status of research on ZORAs are summarized. The common configurations and operation principle of ZORAs are introduced in detail. The behaviors and defects of ZORAs are summarized, and some conventional solutions are described.2. A novel ZORA consisting of new CRLH TL structure is proposed. The return loss, bandwidth, efficiency, pattern and gain are analyzed. The equivalent LC circuit parameters are extracted. The efficiency and the bandwidth are significantly improved by using an L ground compared with the initial antenna. The improved antenna and the initial antenna are fabricated and measured. The experimental results are in good agreement with the simulation results.3. Another type of new CRLH structure is proposed for solving the fabrication problem. This structure is employed for designing a novel ZORA with only one layer of PCB, which makes the antenna structure more optimized and easier to be fabricated. The behaviors of the antenna are analyzed, such as return loss, bandwidth, efficiency, pattern and gain. The property of aperture field distribution is given. The influences of the number of CRLH unit cells and the ground on the antenna performance are analyzed.