Research On Technique Of Surface Wave Driven Plasma Antenna And Its Array

The rapid development of modern mobile communication systems set higher demands toward antennas in front of communication systems. Communication antennas are developing towards the trend of frequency reconfiguration and pattern reconfiguration. Compared with traditional metal antennas, plasma antennas have their special characteristics: Firstly, by controlling the parameters of the plasma, the input impedance, radiation pattern, antenna efficiency and bandwidth of the plasma antenna can be dynamically reconfigured. Secondly, the plasma antenna would turn into a normal dielectric material without excitation, letting its radar cross section negligible. Thus plasma antennas have strategic significance in the military and civil field.The thesis theoretically analyses the radiation mechanism of the surface driven plasma antenna. The numerical model of DI-FDTD (Direct Integration Finite-Difference Time-Domain) method is constructed for the unmagnetized plasma antenna and the model of PLRC-FDTD (Piecewise Linear Recursive Convolution FDTD) method is constructed for the magnetized plasma antenna. On the basis of these models, the influences of plasma parameters on the antenna's near and far field characteristics and the pattern reconfigurability of the antenna is discussed. The main work and creative points of the thesis are as follows:(1) Research on the radiation performance of the unmagnetized plasma antenna and optimization of its performance. Considering requirements in real applications of antennas, a model of a cylindrical plasma antenna encapsulated in a dielectric tube and excited by a capacitively coupling sleeve is built. The DI-FDTD algorithm is utilized to perform simulation on the far-field radiation pattern and the antenna efficiency of the unmagnetized plasma antenna. Simulation results show that the permittivity of the dielectric tube have obvious effects on the far-field radiation pattern and efficiency of the antenna. Thus the radiation performance of a plasma antenna can be optimized by properly setting the permittivity of the dielectric tube.(2) Research on the radiation performance of the magnetized plasma antenna and the technology of dynamically tuning its performance. The PLRC-FDTD method is employed to numerically analysis the input impedance, radiation pattern and antenna efficiency of the magnetized plasma antenna. Numerical results show that the variation of the external magnetic fields have obvious effects on the performance of the antenna. Thus the external magnetic field can be used to dynamically control the bandwidth and radiation pattern of the magnetized plasma antenna.(3) Investigation on the performance of the magnetized plasma antenna with a non-uniform plasma distribution. Considering the situation that the plasma excited in a dielectric tube may be non-uniformly distributed, the model of a both axially and radically non-uniformly distributed magnetized plasma antenna is designed. By using the PLRC-FDTD method, its influence is numerically analyzed. Simulation results show that the non-uniform plasma distribution leads the input impedance of the antenna to shift slightly toward lower frequency and causes the radiation efficiency to fall a bit. However, the magnetized plasma antenna with 15% axial-nonuniform and 10% radial-nonuniform distribution has still achieved 76% radiation efficiency.(4) Research on the radiation performance of the plasma antenna array and design of the pattern reconfiguration. The DI?FDTD numerical model of the plasma antenna array is constructed and utilized to simulation its radiation performance. Simulation results show that the change of plasma parameters of one antenna in the array will draw obvious influences on the radiation pattern and direction of the array. On this basis, the plasma antenna arrays of four elements, six elements and eight elements are designed to realize the dynamic reconfigurability of the radiation pattern.