Study On Fast Hybrid Method For Radiation Performance Of Antennas Mounted On Complex Large-Scale Platform

The rapid development of digital computing and wireless communication have been driving the electromagnetic compatibility to become increasingly significant in the field of military security, especially in solving the complex large weapon platforms, which have the intricate design and fine structures, dense distribution of onboard antennas and nonuniform electrical sizes, such as ships, aircraft and so on. All of these factors have brought great challenges to electromagnetics. Traditional method of moments is not capable of modeling objects with a great number of unknowns due to the limitation of computer resources. High frequency approximation method is suitable for simulating large structures quickly, but unable to analyze complex electromagnetic problems, such as antennas radiation.An efficient iterative Adaptive Integral Method (AIM)-Physical Optics (PO) hybrid method is introduced in this paper for analyzing the performance of antennas mounted on complex electrically-large platforms effectively. The main contents are as follows:(1) The method of moment based on surface-surface configuration is applied to solve the radiation problems, where wire antennas are modeled by equivalent thin-strip structures. The uniform RWG functions used in the surface-surface configuration not only maintain the good accuracy, but also simplify the analysis for the whole system.(2) Detailed work has been done for key points in the implementation of the fast algorithm AIM, including the equivalent transformation of auxiliary base functions, the calculation of the impedance matrix element and FFT acceleration for matrix-vector multiplication. Numerical examples are used to validate the codes.(3) The iterative AIM-PO hybrid method (AIM-PO) is introduced based on traditional MoM-PO hybrid frame to analyze onboard antenna problems, where AIM is employed to effectively simulate the antenna and its surrounding area, and PO is used to handle the rest electrically-large problems. The contribution of PO region is coupled into the matrix equation in the form of additional exciting voltages, which is modified iteratively to achieve stable status of the whole system. The computing complexity is reduced from O(2M2N) to O(Iiter·MN).(4) An efficient iterative AIM-PO hybrid method (EI-AIM-PO) is implemented to speed up the hybrid solution in handling extremely large-scale platforms by employing the effective tree structure, Kd-Tree, which is used on patches of PO region to dramatically accelerate the searching process of the visible part. The computational time of shadow judgement is reduced from O(N2) to O(NlogN) by ray tracing through the Kd-Tree. Numerical examples are discussed to demonstrate the excellent efficiency and accuracy of EI-AIM-PO method.(5) The EI-AIM-PO technique is extended to analyze half-space problems of the antennas installed on large-scale platforms by integrating image theory into the iterative hybrid framework, where the disturbance of infinite planar-medium ground for onboard antennas is described by image current source. Numerical results are used to illustrate the accuracy and efficiency of the approach, compared with the MoM-PO and MLFMM of FEKO.