Integrated Numerical Techniques For Electromagnetic Modeling Of Antenna-Radome Systems Mounted On Electrically Large Complex Platforms

When enclosed by a radome or mounted on a platform,the antenna system is obviously affected by the nearby structures.In modern antenna engineering,it is necessary to evaluate these effects accurately to tune the antenna design parameters.Hence,it is important to analyze the antenna and the surrounding bodies as an entire structure in reasonable computational time with enough accuracy.The surrounding structures such as the radome and the platform are usually of electrically large sizes,and traditional full-wave methods are difficult to deal with these electrically large problems.For these two types of electrically large problems of antenna-radome system and antenna system mounted on platform,multilevel fast multipole algorithm(MLFMA)accelerated hybrid methods,which combine accurate full-wave volume-surface integral equation(VSIE)solution and efficient high-frequency surface integration(SI)and physical optics(PO),are proposed to realize the fast electromagnetic analyses.The major innovative works of this dissertation are as follows:First,in order to solve the problem of radome-enclosed antennas in the receiving mode,a modified surface integration(MSI),which is based on the equivalence principle,is formulated to improve the accuracy of determining the transmitted fields through the radome due to the incident plane wave.Furthermore,a hybrid method called VSIE-MSI,which combines MSI and MLFMA accelerated VSIE,is proposed to analyze electrically large antenna-radome system in receiving mode.VSIE-MSI greatly reduces the number of unknowns,effectively reduces the computational time,and significantly reduces the computational memory requirement.In addition,compared to the case of freestanding receiving array,VSIE-MSI requires little extra memory to consider the effects of the electrically large radome.Second,an iterative VSIE-MSI method is established.This method further improves computation accuracy,by including the effects of shaded wall of radome under plane wave illumination and the mutual interactions between antennas and radome into the numerical solution of the VSIE in an iterative manner.At the same time,MLFMA is adopted to accelerate the computation of reflection on radome inner surface and coupling between antennas and radome.Therefore,compared with the original VSIE-MSI method,the iterative VSIE-MSI method decreases computational complexity to the order of O(Nlog N)and dramatically reduces the cost CPU time with a little cost of memory.Third,the iterative VSIE-MSI method can also be extended to the analysis of the radiation of radome-enclosed antennas.Furthermore,after slightly improved,this iterative method can be adopted to deal with radome including metal-dielectric composite structures,so that this method can analyze more complex radome.That extends the range of application of the iterative VSIE-MSI method.Then,an iterative VSIE-PO method accelerated by MLFMA,in which the full-wave region is divided into sub-regions,is proposed for fast and accurate analysis of radiation and scattering characteristics of antennas on electrically large platforms.The shadowing coefficient in PO is approximate with reasonable accuracy,which makes MLFMA successfully accelerate the calculation of the coupling between full-wave region and high-frequency region.Compared with traditional method of moments-physical optics(MoM-PO),the MLFMA accelerated VSIE-PO method reduces computational complexity and storage complexity to the order of O(Nlog N).At the same time,the VSIE is applied in the MoM region,so that the hybrid method can be used to analyze the problem of metal-dielectric composite antenna system mounted on electrically large conductor platform.Numerical results show that the hybrid algorithm has good numerical accuracy,excellent convergence and computational resources saving.It is an effective method for fast analysis of complex antennas mounted on electrically large platform.Finally,the MLFMA accelerated iterative-based VSIE-LEPO method is proposed by combining VSIE with large element physical optics(LEPO).Because the basis functions adopted in LEPO include phase information,the number of meshes is greatly reduced and the difficulty of modeling and mesh generation is reduced at the same time.In addition,the amount of storage and computation of VSIE-LEPO is in proportion to the number of full-wave sub-regions,and therefore it is suitable for analysis of the problems in which there is very small number of antennas or concentrated distribution of antennas on electrically large platform.In these cases,VSIE-LEPO consumes less computational time and memory than VSIE-PO.