Study Of Simulation And Optimization For Large Antenna And Array Based On Paralle FDTD

In the research of long distance communication, radar detection, deep sapce detection and electronic attack, the antennas with high gain and good directional performance have played an important role for a long time. In order to meet these requirements, reflector antennas with large diameter or large scale arrays are used in engineering, and this may lead to large electrical size of antennas. In the simulation and design of large reflector antennas and large arrays, the traditional methods such as high frequency methods, full wave methods and Array synthesis methods can not take calculation accuracy and efficiency into account. To solve these problems, the fast and accurate methods to simulate beam waveguide reflector antennas with large electrical size and ultra wideband antenna arrays are studied. So the design cycle will be shortened, and the cost will be reduced. The main contributions of this paper are briefly summarized as follows.Firstly, in the full-wave simulation of large antennas and arrays, the main problem is long time and large memory cost. In order to solve the problem, finite different time domain(FDTD) method with non-uniform meshes and its key technologies are studied. The calculation time of FDTD method is reduced significantly. Then the parallel FDTD method with non-uniform meshes and symmetric boundary condition is presented to solve the radiation problems of antennas with symmetric structures, the mesh number and calculation time are reduced by half. The parallel algorithm is used to simulate arc tapered transformed-TEM horn antenna and reflect array antenna, and the accuracy of the algorithm is verified. At last, the parallel etfficiency of the algorithm is tested. The results indicate that the parallel efficiency reaches 80%.Secondly, a hybrid method combined by body-of-revolution FDTD (BOR-FDTD) with three dimension non-uniform meshed FDTD is realized, and the software JBORAO is designed. Firstly, a software used for the optimization of rotational symmetry antenna is achieved, which is based on parallel BOR-FDTD and hybrid optimization algorithm. The software is used for the optimization of conical horn antennas and fast simulation of rotational parabolic antennas. As the beam waveguide reflector antenna has a large electrical size, it is difficult to solve the radiation problem with full wave method. But the structure of the beam waveguide is partial rotational symmetry, so the hybrid method combined by body-of-revolution FDTD (BOR-FDTD) with three dimensional non-uniform meshes FDTD is used. The calculation time is reduced significantly while the accuracy is also ensured.What is more, the parallel technique is used to speed up the calculation. Then the hybrid method was used to simulate a scaled model of the beam waveguide reflector antenna, the results are in good agreements with EM software. At last, a technique combined by the hybrid method and optimization algorithm is presented, which is used for the optimization of an X-band beam waveguide reflector antenna. The gain of the beam waveguide reflector antenna is improved significantly, and the side lobe level (SLL) is also reduced.Thirdly, a method used for the fast calculation of time-domain far field radiation for ultra wide band pulse antenna array is studied. Based on active element pattern (AEP), a fast method to calculate the power pattern and energy pattern of- large arrays by using the time-domain far fields of a small array is presented. Firstly, the far fields of an arc tapered transformed-TEM horn antenna array with five elements are used to calculate the far fields of an array with eleven elements. By comparison with pattern multiplication method and full wave method, the results indicate that the method in this paper can take the array coupling and calculation efficiency into account. What is more, an array with eleven elements has been optimized, the side lobe level was reduced after optimization. Then the fast method for planar arrays is studied, the far fields of an array with 121 elements (11×11) has been calculated by using the far fields of an array with 25 elements (5×5). The accuracy of the method has been verified, and the power pattern and energy pattern of an array with 450 elements (15×30) has also been calculated. At last, the method combined with Taguchi algorithm is used to analysis the effects from the unstable factors of arrays.Fourthly, the electromagnetic interaction of the ground targets and radiation fields from ultra wide band antenna is studied. Firstly, a half-space FDTD method with non-uniform meshes is presented. The 1D modified Maxwell's equations are discretized in non-uniform meshes, and the plane wave is injected into half space problems which contains layered ground, the meshes and calculation time are reduced. Then the method is used to simulate the scattering problems of aground objects and buried objects which interacted by Gaussian pulse plane wave, the accuracy of the method is verified. What is more, based on the plane wave approximation of the radiation far field from antennas, the coupling problems of aground oscilloscope case and buried mine which interacted by the radiation fields of an arc tapered transformed-TEM horn antenna is simulated. Compared with the uniform meshes FDTD method, the calculation speed of the presented method is improved. At last, the building couplings interacted by radiation fields of the airborne ultra wide band antenna array is simulated.