Metamaterial Based Multi-band Antenna

Metamaterial is currently a hot research topic. And multi-band antenna, with a small size and low cost, therefore be a good candidate for communication. When metamaterial is used in multi-band antenna, it provides new elements for antenna development. The main content of this paper is to study the impedance and radiation characteristics of metamaterial-based multi-band antenna, it aims to design a multi-band as well as multi-mode antenna, and to improve the antenna performance.The main contents are as follows:First, a triple-band antenna based on the complementary ring resonator (CSRR) and composite left/right-handed transmission line (CRLH) is designed, the principles of CSRR and CRLH are explained, their equivalent circuit models are built, then my antenna structure is designed, simulation and analysis results are given. By adjusting the structure of antenna, the impedance of the antenna is improved. The operating bandwidth of -10dB, respectively, at three antenna operating frequency is 3.85～4.01GHz,5.46～6.76GHz, and 7.986～8.121GHz, the relative bandwidth is 4%,21.28%, and 1.7%. Then according to the results of simulated surface current, the principle of the triple-band antenna is theoretically analyzed well. Finally, the measurements of radiation characteristics and impedance characteristics of the antenna are obtained, and the results are compared with the simulation results, which are in good agreement. The cause of small errors is also analyzed.Then two kinds of dual-band circular-polarized antennas based on metamaterial are designed. The coaxial-fed dual-band circular-polarized antenna is fed by a coaxial line on a single point, and the microstrip-fed dual-band circular-polarized antenna is fed by a microstrip line. The matching of the antenna is also completed. For the first antenna fed by coaxial, at first, the geometry is completed, which is simulated by CST. After dual-band circular-polarized mode of antenna is achieved, the antenna structure is changed slightly to achieve better results. Then the principle of the antenna is analyzed. When adding a metal slit on the patch, a left-handed capacitor structure is achieved, with via between the patch and the floor, the left inductor is achieved, forming a metamaterial-based antenna structure. Then the equivalent circuit model of the antenna is given and analyzed, including the principle of circular polarization. Then, for the coaxial-fed antenna, the geometric model is finished at first, and then the simulation results are used to change the structure of antenna slightly to achieve better results. The -10dB bandwidth of the antenna is 2.085～2.089GHz and 2.310～2.343GHz, with gain of 2.6dB and 6.3dB. For the microstrip-fed antenna, with the use of metal on the gap of the patch, left capacitor structure is formed. But for inductive of antenna, it is formed by two vertical metal stub. When the angle between them is proper, a surface current angled of 90° can be gained, achieving a circular-polarized antenna. The -10dB bandwidth of the antenna is 2.17～2.20GHz and 2.45～2.46GHz, with gain of 8.1dB and 7.4dB.