Study And Design On The Frequency Reconfigurable Antenna Based On Metamaterials

With the rapid development of electronics and wireless communication industry, the requirements of miniaturization of equipment, high gain, multiband and other indicators are more and more strict. As the signal receiver and transmitter of the system, the miniaturization of antenna is of great importance. The frequency reconfigurable antenna can improve the performance by changing its electrical characteristics, thereby reducing the volume of the communication system, improving the compatibility of the system and reducing the cost. Over the past few years, the metamaterials which has some special physical properties such as negative permittivity, negative permeability and negative refractive index have attracted great attention. A lot of researchers put forward that metamaterials can be used in the traditional antenna to achieve the purpose of miniaturization and multi band of antenna. This paper mainly studies the application of the metamaterials in the frequency reconfigurable antenna. By changing the structure parameters of the metamaterials unit, the resonant mode of antenna can be changed and then the work frequency can be reconstructed. The feasibility of this method is verified through the dispersion characteristics of the metamaterial unit The main work and achievements are summarized as follows:Firstly, this paper briefly introduces research background and the development status of the frequency reconfigurable antenna and metamaterials. And then the left-handed transmission line equations, composite right/left-handed transmission line equation and zeroth order resonant theory are introduced. Finally, this paper briefly introduces the theory of the antenna and the coplanar waveguide.Secondly, a frequency reconfigurable antenna based on ENG-TL(Epsilon-Negative Transmission Line) is designed. The antenna consists of two ENG-TL units. By controlling the ON/OFF status of switches between the metamaterials unit and the radiating patch, the frequency of the antenna can be reconstructed. The antenna has simple structure and stable performance. It has three resonant modes. The work frequency of the antenna covers WLAN(2.4-2.484GHz), Wi MAX(3.3-3.69GHz) and the downlink of C band satellite communication system(3.7-4.2GHz).Finally, two small frequency reconfigurable antennas are designed based on the CRLH-TL(Composite Right/Left-Handed Transmission Line). The two antennas both have two reconstruction modes. One of them only has two single bands. And the other antenna’s mode can be changed between a single band and a dual band. The reconfigurable modes can be changed by controlling the switch status conveniently. These two antennas have size of only 0.082λ×0.111λ×0.004λ(λ correspond to 1.76 GHz wavelength). The simulated and measured results indicate that the antennas maintain a stable radiation pattern when the work bands are changed. The antennas can be used in WLAN(2.4-2.484GHz/5.725-5.825GHz) system, Wi Max(2.5-2.69GHz), ISM2.4GHz and UMTS1750-1780 MHz system.