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In this paper we propose the use of the Multilevel Domain Differentiated (MDD) model to analyze structures with fine details, non-uniform meshes, and large overall sizes. The MDD method is able to significantly improve the spectral properties of the EFIE MoM matrix for broad-band analysis, employing a multi-scale representation of the solution to deal differently with different scales. Here the method...
Several approaches to improve the numerical efficiency of the spectral-to-spatial domain transformation of the single-layered cylindrical mixed-potential Green's function are presented. Additionally, a method to compute the radiated far-field due to a previously determined equivalent surface current distribution on the substrate/air interface is presented as well. The numerical efficiency depends...
Electric propulsion is a commercially attractive solution for attitude and position control of geostationary satellites. Hall-effect ions thrusters generate a localized plasma flow in the surrounding of the satellite, whose impact on the communication system needs to be qualitatively and quantitatively assessed. An electromagnetic modelling tool was developed and integrated into a commercial numerical...
This communication presents promising applications of the integral equation formulation of the inverse source problem. The technique is based on the extraction of equivalent sources on a 3-D closed surface enclosing the Antenna Under Test (AUT) from near or far field measured radiation patterns upon rigorous application of the equivalence principle. Such sources allow malfunction detection and design...
A method to efficiently apply Domain-Decomposition (DD) to the MoM via the Synthetic Function eXpansion (SFX) is presented. Special emphasis is placed on the automatic generation of block subdivision of an arbitrary structure, which is key for all DD approaches. The DD-SFX approach is integrated within an FFT-based fast solver. Numerical experiments are presented in order to validate the method.
The electromagnetic solution of surface integral equations for perfect conductors is not unique when the scatterer is a closed object and the frequency is an eigenfrequency of the interior cavity. A possible solution known in literature is the regularization of the problem through a dual surface approach. Here a simple and automatic procedure to discern closed and open portions of an arbitrary object,...
Entire-domain basis functions are introduced for the analysis of scattering from bodies with flat portions, and of radiation from planar apertures; they are defined via the application of the sampling theorem of Shannon. These basis functions are particularly convenient for polygonal contours; however, arbitrary contours can be treated in the same framework with a very minor pre-processing time. A...
In this paper we present the design of a quad-band reconfigurable antenna for GSM/DCS/PCS communications, to be mounted inside vehicles. The optimization technique here adopted is based on the Genetic Algorithm, coupled with an efficient full-wave analysis. This approach is applied to a realistic sample case. The performances, in terms of antenna matching, achieved through this novel approach are...
In this communication we present a novel algorithm to design a sparse array starting from a mask (inequality) specification on the radiation pattern. The algorithm allows constraints on the excitation coefficients (e.g. amplitude dynamic, including phase-only) and considers the radiation pattern of the elements (which need not be all equal). The proposed algorithm exploits a joint application of alternating-projection...
This work removes this limitation and generalizes our previous approach to the case of completely unstructured meshes. Generalized modified solenoidal functions will be presented that, while keeping the condition number of the EFIE solenoidal part constant with the number of unknowns, will be a linear combination of standard Rao Wilton-Glisson (RWG) basis functions defined on arbitrary meshes.
Full-wave optimisation of large arrays is computationally intensive problem even with the most advanced solvers. The paper presents a procedure for the full-wave optimisation of arrays based on a space mapping (SM) procedure. The approach combines the efficiency of MoM-based accelerated modelling techniques with physics-based coarse models to reach unprecedented efficiency in terms of accuracy and...
This communication presents the application of the source reconstruction technique to the processing of measured data in tasks such as the filtering of disturbances such as undesired coupling with the supporting structure or the feeding and in NF-NF transformation. The filtering technique is based on the dual-equation formulation of the source reconstruction method in order to obtain equivalent sources...
A planar periodic structure obtained by 2D repetition of a unit cell consisting of a width-modulated microstrip line is considered. The variation of the modulation parameters in different regions of the surface can be exploited to locally control the phase velocity of the surface waves and the surface impedance of the structure. In this context, analysis and solutions are presented aiming to guarantee...
We want to reconstruct equivalent sources on a “reconstruction surface” ΣR that encloses a volume Ω where the equipment under test (EUT) lies; the EUT encompasses the antenna(s) and possible neighboring scatterers, as need in the application of interest. We employ the equivalence theorem to represent the fields outside the reconstruction surface ΣR and on it. Note that it is typically desirable or...
This paper presents a new complete entire-domain basis functions set for the current induced on a smooth curved portion of a scatterer surface. The set is obtained generalizing to the case of curved surfaces the Generalized Shannon Basis functions introduced in [3]. The basic idea is presented here together with preliminary numerical results.
This communication presents a novel technique to deal with undesired interaction of the AUT with cables and other nearby disturbances. Its key features are: i) it allows removal of the effect of disturbances on antenna pattern, ii) it requires only approximate geometrical knowledge of the AUT and disturbing objects and iii) it is a fast data post-processing step that puts no special requirements on...
Multiresolution (MR) basis has been effectively applied as preconditioner of the electric field integral equation (EFIE) discretized with the method of moments (MoM). The developed MR basis can be generated on completely arbitrary shaped geometries, without any topological limitation, and has been extended to structures formed by surfaces connected to wires. The MR basis functions are described as...
We have proposed an algorithm able to identify open and closed parts of a generic geometry. This information is essential to apply different integral equation formulations to different parts of the structure: the EFIE to open parts and the CFIE to the closed ones. The application of the CFIE is necessary to avoid internal resonances of the structure, but this formulation can not be applied simply...
In this work we presented a new optimization procedure that allows one to reduce SAR in MRI exam and control the polarization. Contrary to other shimming procedures controlling the polarization of the field consent us to control the power delivered to the entire system. Consequently SNR is improved and the proposed method would be used also in 1.5 T and 3 T MRI. Such kind of technique was tested in...
Work in the direction of multi-functional antennas has been done in the past with a reconfigurable antenna tunable on a broad band. This communication presents an approach whereby a single multi-port antenna reconfigurable by switches is designed to serve several systems. A highly efficient full-wave simulation tool based on the Method of Moments (MoM) makes it practical to perform electromagnetic...
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