Optimal Design Of Antennas And Scattering Characteristic Research Of Moving Objects Based On FEM

With the improvement of numerical processing techniques, Finite Element Method (FEM), developed on the basis of interpolation and variational principle, is widely used in research in the field of electromagnetics with its powerful ability to process complex problems and stable and accurate solution results. In wireless systems, all electromagnetic waves are transmitted and received by antennas. Thus, optimal design of antennas is essential for a wireless system. Electromagnetic scattering analysis of high-speed moving objects is an important topic in computational electromagnetics, and has great significance on the development of stealth and anti-stealth technology of high-speed moving objects and the research in the field of space-borne microwave remote sensing. The thesis mainly focuses on the optimal design of antennas and electromagnetic scattering analysis of moving objects based on FEM.Firstly, the genetic algorithm is utilized to optimize a dual-band circularly polarized antenna which could be used in BeiDou Navigation Satellite System (BDS). The antenna structure can be reconstructed adaptively according to module value of return loss and axis ratio with the combined programming for High Frequency Structure Simulator(HFSS) and Matlab, which simplifies the design process of antennas enormously. By embedding two pairs of T-shaped slots close to the boundary of a circular patch, this antenna can operate in the bands of uplink and downlink of BDS. Compared to the traditional process of antenna design, antenna optimization with genetic algorithm can adjust the antennas’ structure flexibly and obtain a dual-band circularly polarized antenna with simple structure and good performance.Secondly, electromagnetic scattering analysis of moving objects is studied with the Lorentz transformation based on FEM. This method not only has good adaptability and high accuracy of FEM, but also reduces the calculation error in the electromagnetic scattering analysis of moving objects combined with Lorentz transformation. The method is verified by calculating the reflection and transmission coefficients of infinite moving dielectric slab. On basis of that, the radar cross sections (RCS) and Doppler effect of two-dimensional conducting objects in different velocities are calculated under the circumstances of various incident angles and objects’materials. Numerical examples show that the effects of the motion on the radar cross sections and Doppler are non-negligible for high-speed objects. The Doppler effects are related with the incident angle, the velocity vector of the object and the scattering angle, and symmetrical corresponding to the direction of the motion of the body.