Fast and Accurate Simulation Technique for Large Irregular Arrays

A fast full-wave simulation technique is presented for the analysis of large irregular planar arrays of identical 3-D metallic antennas. The solution method relies on the Macro Basis Functions (MBF) approach and an interpolatory technique to compute the interactions between MBFs. The Harmonic-polynomial (HARP) model is established for the near-field interactions in a modified system of coordinates. For extremely large arrays made of complex antennas, two approaches assuming a limited radius of influence for mutual coupling are considered: one is based on a sparse-matrix LU decomposition and the other one on a tessellation of the array in the form of overlapping sub-arrays. The computation of all embedded element patterns is sped up with the help of the non-uniform FFT algorithm. Extensive validations are shown for arrays of log-periodic antennas envisaged for the low-frequency SKA (Square Kilometer Array) radio-telescope. The analysis of SKA stations with such a large number of elements has not been treated yet in the literature. Validations include comparison with results obtained with commercial software and with experiments. The proposed method is particularly well suited to array synthesis, in which several orders of magnitude can be saved in terms of computation time.Comment: The paper was submitted to IEEE Transaction on Antennas and Propagation on 01 - Feb.- 2017. The paper is 12 pages with 18 figure

An Ultra-wideband Battery-less Positioning System for Space Applications

An ultra-wide bandwidth (UWB) remote-powered positioning system for potential use in tracking floating objects inside space stations is presented. It makes use of battery-less tags that are powered-up and addressed through wireless power transfer in the UHF band and embed an energy efficient pulse generator in the 3-5 GHz UWB band. The system has been mounted on the ESA Mars Rover prototype to demonstrate its functionality and performance. Experimental results show the feasibility of centimeter-level localization accuracy at distances larger than 10 meters, with the capability of determining the position of multiple tags using a 2W-ERP power source in the UHF RFID frequency band.Comment: Published in: 2019 IEEE International Conference on RFID Technology and Applications (RFID-TA

Simulation of a Radio-Frequency Quadrupole with the Method of Moments

The Myrrha project aims at developing a sub-critical reactor driven by a LINear ACcelerator (LINAC). A Radio-Frequency Quadrupole (RFQ) is a RF cavity placed at the beginning of the accelerator. Its goal is focusing the beam, bunching it and giving it its first acceleration. The quality of the beam inside further sections of the LINAC is very sensitive to the quality of the output beam of the RFQ. For a high-current beam LINAC, the undesired effects due to repulsive forces between charges may be very strong. The goal of this thesis is to develop a fast and accurate solver for RFQ simulations. The Method of Moments (MoM) is a boundary element solver widely used to solve the harmonic Maxwell’s equations for radiation and scattering problems. The MoM is used for the first time in this thesis to obtain the electromagnetic fields produced inside the accelerator by the RF source. In order to reduce the computation time, innovative fast methods for low-frequency problems with the MoM have been developed: they are based on an appropriate pre-conditioner and some SVD compressions on top of a local approximation of the Green function for radiation. Besides, a beam dynamics solver based on an efficient particle-to-particle interaction has been developed. It relies on several smart physical approximations allowing a good complexity and on an efficient implementation on Graphics Processor Unit (GPU) with OpenCL, while preserving in their concept a good platform independence.(FSA - Sciences de l'ingénieur) -- UCL, 201

Stabilization of the modelling of a Radio-Frequency Quadrupole based on quasi-Helmholtz projectors

International audienceThis paper presents a stabilization of a Radio-Frequency Quadrupole simulation based on the quasi-Helmholtz projectors. A boundary element method applied to this case undergoes a low-frequency breakdown i.e the associated system of equations becomes increasingly ill-conditioned for decreasing frequencies. This in practice implies that the convergence of iterative methods which are used to solve the linear system is poor. This paper reports that a quasi-Helmholtz projectors based stabilization is sufficient to handle the level of realism required by applications

A kernel-based method for dense-mesh problems

Fast methods for the evaluation of the EFIE operator at a given current distribution undergo some difficulties at low frequency. In particular,it is well known that the MLFMA at low frequency undergoes a breakdown due to the translation operator that becomes unstable. In this paper, an innovative method that provides a fast way to calculate the evaluation of the EFIE operator at a given current distribution and for low-frequency problem is presented. It is based on local Taylor approximation of the Green’s function coupled with one-time (once and for all geometry) SVD compression technique

Mutual coupling analysis in non-regular arrays of SKALA antennas with the HARP approach

Wideband arrays devoted to radio-astronomy are analyzed. The Macro Basis Functions (MBFs) approach is used and improvements on the interpolatory approach are proposed for the fast interaction between MBFs: application to wire-antennas, DFT approach for the harmonic decomposition and specific to extremely small distances between antennas

Simulation of a radio frequency quadrupole with the Method of Moments

A Radio Frequency Quadrupole (RFQ) is an essential part of linear accelerator (LINAC). It is situated at the very beginning of the accelerator and has three important functions: focusing, bunching and acceleration. The RFQ prepares the beam before its injection into the strong acceleration cavities and so it impacts the behaviour of the beam in the whole accelerator. Hence, it must be designed as reliable and efficient as possible. At the present time, the simulation of the electromagnetic fields and beam dynamics are carried out with some approximations in order to obtain a reasonable computation time. However, faster and more accurate solvers would first allow us to better understand the RFQ technology for high beam currents and second would potentially allow us to perform some numerical optimization. Our main objective is to develop a fast and accurate solver for the electromagnetic fields and for the beam dynamics. Our laboratory is specialized in fast methods for the electromagnetic fields simulation of antennas. Our solvers are based on the Method of Moments (MoM) in the frequency domain. This method could be applied as well for the electromagnetic fields simulation in accelerating cavities. One of the main advantages of the MoM in comparison to finite elements is that it requires only unknowns on the surface of the cavity. For high beam current, it would be very convenient to be able to calculate simultaneously the equations of motion and the Maxwell’s equations since the fields scattered due to the space charge can be as strong as the source fields. Such a simulation is so-called a self-consistent simulation

Stabilization of the modelling of a radio-frequency quadrupole based on quasi-Helmoltz projectors

This paper presents a stabilization ofa Radio-Frequency Quadrupole simulation based on the quasi-Helmholtz projectors. A boundary element method applied to this case undergoes a low-frequency breakdown i.e the associated system of equations becomes increasingly ill-conditioned fordecreasing frequencies. This in practice implies that the convergence of iterative methods which are used to solve the linear system is poor. This paper reports that a quasi-Helmholtz projectors based stabilization is sucient to handle the level of realismrequired by applications

Low-cost near field pattern measurement technique for aperture array characterization

This paper describes a low-cost innovative technique to characterize aperture arrays based on a near field pattern measurement. This measurement is used to validate a numerical method code, based on the method of moments, capable of realizing accurate electromagnetic simulations of very large non-regular arrays containing up to thousands of elements which are tens of wavelengths in diameter. A practical application of the technique and the code can be found for low frequency aperture arrays in radio astronomy applications, such as the SKA telescope

Characterization of SKA-AAlow Antenna elements in the array environment

The electromagnetic modeling and testing is presented for antenna elements devoted to the low frequency band of the Square Kilometre Array (SKA) telescope [1]. Covering a band from 70 to 450 MHz, these elements consist on a log-periodic dipole array (LPDA) model and they have been designed for maximum sensitivity across the band in the region +/- 45 degrees from zenith. A 16-element array (AAVS0 - Aperture Array Verification System 0) has been built in Lords Bridge, Cambridge, UK, and it is being tested to validate the electromagnetic properties of the antenna elements and front-end. We focus on the modeling of these elements and compare simulated and measured data for simulation software validation