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The monostatic radar cross section (RCS) is an important design parameter for many applications, but accurate RCS prediction of an electrically large structure continues to be a challenging task. High accuracy demands and a complicated geometry often mean that asymptotic methods are not applicable, while a full-wave method has traditionally required very large computational resources. In the present...
Waveguides with anisotropic surface impedance boundaries have been investigated for the purpose of matched feeds for offset reflectors. Matched feeds employ higher order waveguide modes to cancel out cross polarization introduced by the offset geometry. Since the higher order modes propagate at different speeds than the fundamental mode in conventional waveguides, it is challenging to meet phase relationship...
We present a method that enables full-wave analysis of electrically large antennas and platforms, e.g., a detailed telecommunication satellite at Ka-band. Owing to the efficient formulation, even large problems can be solved on relatively modest computing platforms such as laptops or off-the-shelf workstations. The method is based on the higher-order Method of Moments, accelerated by Multi-Level Fast...
Matched feed horns aim to cancel cross polarization generated in offset reflector systems. An analytical method for predicting the mode spectrum generated by inclusions in such horns, e.g. stubs and pins, is presented. The theory is based on the reciprocity theorem with the inclusions represented by current sources. The model is supported by Method of Moments calculations in GRASP and very good agreement...
A Higher-Order Multilevel Fast Multipole Method (HO MLFMM) is presented for the efficient calculation of waveguide scattering parameters in cases where several reflector feeds are mounted on electrically large satellite platforms. The efficiency is obtained by: 1) using a Block Krylov method for solving the HO MLFMM problem for the required large number of right-hand sides and 2) implementing an out-of-core...
We present recent advances in the RF modeling of electrically large antennas and platforms, with an emphasis on reflector antennas and satellite platforms. The Higher-Order Multilevel Fast Multipole Method (HO MLFMM) was introduced recently in the commercial software tool GRASP, and this algorithm is employed in this paper due to the very low memory requirements and the need for very high accuracy...
The inherently high cross polarization of prime focus offset reflector antennas can be compensated by launching higher order modes in the feed horn. Traditionally, the bandwidth of such systems is in the order of a few percent. We present a novel design procedure where the entire matched feed and reflector system can be efficiently optimized. This allows the design parameters of the matched feed to...
The challenges related to the increasing physical size of satellite platforms carry over to a number of related areas, including the design of Compact Antenna Test Ranges (CATRs) capable of handling such structures. In the present paper, we consider the design of a large CATR and use state-of-the-art Computational Electromagnetics (CEM) software, based on full-wave methods to fully include the important...
The design of electrically large antennas can be a significant challenge for computational electromagnetics (CEM) tools, particularly during the final stages of the design process where there are strict requirements for the accuracy. In the present paper, we consider the use of a newly developed accelerated Physical Optics (Fast-PO) and show that this approach allows for a timely and accurate solution...
This paper presents two new modelling algorithms that was recently added to the commercially available GRASP software package for electrically large antenna and scattering problems. In particular, a new higher-order multilevel fast multipole solver (HO-MLFMM) provides very high simulation accuracy while requiring significantly less memory and CPU time than the commonly available low-order MLFMM. At...
We apply two algorithms to full-wave analysis of electrically large reflector antennas with complex surroundings. The new algorithms are a higher-order MLFMM, yielding a considerably faster solution than a low-order MLFMM, and a fast algorithm for current integration. The new techniques allow a significant reduction of the computational burden, thereby extending the range of problems that can be solved...
We consider the application of full-wave methods to electrically large structures with emphasis on an implementation that allows modest computing resources to be used even for very large problems. First, we highlight the recent development of a Multi-level Fast Multipole Method (MLFMM) implementation based on Higher-Order (HO) basis functions, which allow significant time and memory reductions as...
A higher-Order (HO) quadrilateral mesher is presented along with a HO method of moments formulation for unconnected meshes. A numerical example is presented to validate the new formulation.
ABSTRACTAn alternative parameter‐free adaptive approach for the grouping of the basis function patterns in the multilevel fast multipole method is presented, yielding significant memory savings compared to the traditional Octree grouping for most discretizations, particularly when using higher‐order basis functions. Results from both a uniformly and nonuniformly meshed scatterer are presented, showing...
An efficient Body of Revolution Method of Moments formulation is presented in which the unknown surface current density on the generatrix of the rotationally symmetric scatterer is expanded in terms of higher-order hierarchical Legendre basis functions. Careful attention has been paid to fast evaluation of the involved modal Green's functions. The efficient formulation is particularly useful for the...
Results using a new translation operator for the Multi-Level Fast Multipole Method are presented. Based on Gaussian beams, the translation operator allows a significant portion of the plane-wave directions to be neglected, resulting in a much faster translation step.
A generalised admittance matrix technique that enables an accurate full-wave analysis of typical integrated lens antennas in less than 2 minutes is presented. The fast analysis is obtained by rigorously combining two efficient higher-order MoM solvers; a general 3D-MoM solver and a fast BoR-MoM solver for structures with rotational symmetry. The method is very suitable for numerical optimisation of...
This paper presents an efficient technique for full-wave analysis of dielectric lenses with integrated feeding. The feeding section is analysed with a higher-order 3D-MoM algorithm, while the rotationally symmetric lens is analysed with a higher-order BoR-MoM. Each method allows the extraction of a generalized admittance matrix that fully characterizes the region in question. The individual matrices...
The design and optimization of multi-faceted reflect-arrays for satellite applications are presented. The objective of this work is to investigate the performance of a multi-faceted reflectarray designed using a direct optimization technique. To this end, a single-layer multi-faceted reflectarray, that produces a contoured beam for a European coverage in a bandwidth of 17% has been designed. The performance...
The Multilevel Fast Multipole Method (MLFMM) allows for a reduced computational complexity when solving electromagnetic scattering problems. Combining this with the reduced number of unknowns provided by Higher-Order discretizations has proven to be a difficult task, with the general conclusion being that going above 2nd order is not worthwhile. In this paper, we challenge this conclusion, providing...
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