Hybrid LEGO-EFIE method applied to antenna problems comprising anisotropic media

Linear embedding via Green’s operators (LEGO) is a domain decomposition method in which complex radiation and scattering problems are modelled and solved by means of interacting electromagnetic "bricks". We propose an extension of LEGO able to handle bodies with anisotropic constitutive parameters and metallic objects (e.g., antennas). Since the anisotropic objects are dealt with LEGO, and the metallic parts are treated with the electric field integral equation (EFIE), we refer to the overall approach as hybrid LEGO-EFIE. The characterization of an electromagnetic brick which embeds an anisotropic object requires solving a volume integral equation (VIE). Since this procedure is carried out for each brick independently, the LEGO approach per se is extremely advantageous over the direct solution of a global VIE for all the bodies at once. Nonetheless, we further mix the hybrid LEGO-EFIE approach with the eigencurrents expansion method in order to tackle relatively larger problems. The technique is used to analyze a reconfigurable plasma antenna array (PAA) comprised of magnetized-plasma tubes placed around a two-dipole antenna array

Development of Electromagnetic Codes to Analyze and Optimize Satellite Propulsion Systems and Communication Antennas

Satellite communication systems have demonstrated their essential role providing timely services for disaster management in a variety of distress situations. Their effectiveness requires high mapping and pointing accuracy in terms of displacement capability, and high gain, high bandwidth, directional, and reconfigurable antennas in terms of communication capability. A Helicon plasma thruster, and an enhanced communication system meet the aforementioned requirements. The former is an electric plasma-based propulsion system that provides an high accuracy attitude control, while the latter could be either an optimized state-of-the-art antenna or an innovative concept based on plasma antennas. In this research work, several computationally efficient codes have been developed to analyze, design and optimize the helicon plasma thruster, and the antenna for an enhanced communication system. The present work progresses starting from the definition of the requisites, and continues to describe the innovative numerical methods: the SPIREs finite-difference frequency-domain electromagnetic solver for magnetized plasma cylinders; the WAVEQM equilibrium condition solver for radiofrequency heated plasmas; the PARTYWAVE particle in cell code for cylindrical geometries, and the Moment Method for antenna design. Their numerical accuracy has been verified, and they have been validated against physical cases

Beam-forming capabilities of a plasma circular reflector antenna

A gaseous plasma antenna array (PAA) is an aggregate of plasma discharges and possibly conventional metallic radiating elements, and it constitutes a promising alternative to metallic antennas for applications in which fast reconfiguration of radiation pattern, and gain is desired; such properties can be achieved by exploiting the electronic switch on/off condition of plasma discharges, and tuning of the plasma parameters. Here, the authors present a reconfigurable PAA that features a central metallic half-wavelength dipole working around 1.45\u2005GHz, surrounded by a planar circular lattice of cylindrical plasma discharges. Customised plasma discharges have been realised, and filled with argon gas at 2\u2005mbar so as to have a complete control on the plasma discharge properties (e.g. plasma frequency, collisional frequency). The magnitude of the reflection coefficient, and the gain pattern on the H-plane have been investigated numerically and experimentally; numerical and experimental results exhibit a good agreement and show that the central intrinsically omnidirectional antenna can provide simple beamforming capabilities upon turning on a subset of plasma discharges; as these plasma discharges are turned on, the authors have observed a maximum gain of 3c5\u2005dBi, a half-power beam width of 80 18, and an angular steering resolution of 3c15 18

Development of Electromagnetic Codes to Analyze and Optimize Satellite Propulsion Systems and Communication Antennas

Satellite communication systems have demonstrated their essential role providing timely services for disaster management in a variety of distress situations. Their effectiveness requires high mapping and pointing accuracy in terms of displacement capability, and high gain, high bandwidth, directional, and reconfigurable antennas in terms of communication capability. A Helicon plasma thruster, and an enhanced communication system meet the aforementioned requirements. The former is an electric plasma-based propulsion system that provides an high accuracy attitude control, while the latter could be either an optimized state-of-the-art antenna or an innovative concept based on plasma antennas. In this research work, several computationally efficient codes have been developed to analyze, design and optimize the helicon plasma thruster, and the antenna for an enhanced communication system. The present work progresses starting from the definition of the requisites, and continues to describe the innovative numerical methods: the SPIREs finite-difference frequency-domain electromagnetic solver for magnetized plasma cylinders; the WAVEQM equilibrium condition solver for radiofrequency heated plasmas; the PARTYWAVE particle in cell code for cylindrical geometries, and the Moment Method for antenna design. Their numerical accuracy has been verified, and they have been validated against physical cases.Gli apparati di comunicazione satellitare hanno dimostrato un ruolo essenziale nel fornire supporto tempestivo nella gestione di situazioni di emergenza. La loro efficacia richiede elevate precisioni di mappatura e di puntamento riferite al controllo d'assetto, mentre richiedono antenne con elevato guadagno, larghezza di banda e riconfigurabili in riferimento alle comunicazioni. Un propulsore elettrico al plasma di tipo Helicon è in grado di soddisfare i requisiti di mappatura e puntamento garantendo un controllo d'assetto di estrema precisione, mentre i requisiti pertinenti al sistema di comunicazione possono essere soddisfatti da una versione ottimizzata delle attuali antenne, o da una antenna innovativa basata sulle antenne al plasma. In questo lavoro di ricerca sono stati sviluppati diversi codici, computazionalmente efficienti, pensati come strumenti di analisi, progettazione e ottimizzazione per propulsori al plasma Helicon e per sistemi di comunicazione avanzati. Il lavoro presentato in questo documento progredisce dalla definizione dei requisiti fino ad una descrizione dettagliata dei singoli codici: SPIREs un solutore elettromagnetico nel dominio della frequenza per plasmi magnetizzati, WAVEQM un solutore delle condizioni di equilibrio per sorgenti di plasmi in radiofrequenza, il codice particellare PARTYWAVE, e un codice per la progettazione di antenne basato sul Metodo dei Momenti. L'accuratezza numerica dei singoli codici è stata verificata, ed essi sono stati validati con test significativi da un punto di vista fisico

A comparative study of radiofrequency antennas for Helicon plasma sources

Since Helicon plasma sources can efficiently couple power and generate high-density plasma, they have received interest also as spacecraft propulsive devices, among other applications. In order to maximize the power deposited into the plasma, it is necessary to assess the performance of the radiofrequency (RF) antenna that drives the discharge, as typical plasma parameters (e.g., the density) are varied. For this reason, we have conducted a comparative analysis of three Helicon sources which feature different RF antennas, namely, the single-loop, the Nagoya Type-III, and the Fractional helix. These antennas are compared in terms of input impedance and induced current density; in particular, the real part of the impedance constitutes a measure of the antenna ability to couple power into the plasma. The results presented in this work have been obtained through a full-wave approach which (being hinged on the numerical solution of a system of integral equations) allows computing the antenna current and impedance self-consistently. Our findings indicate that certain combinations of plasma parameters can indeed maximize the real part of the input impedance and, thus, the deposited power, and that one of the three antennas analyzed performs best for a given plasma. Furthermore, unlike other strategies which rely on approximate antenna models, our approach enables us to reveal that the antenna current density is not spatially uniform, and that a correlation exists between the plasma parameters and the spatial distribution of the current density

Hybrid LEGO-EFIE method applied to antenna problems comprising anisotropic media

Linear embedding via Green’s operators (LEGO) is a domain decomposition method in which complex radiation and scattering problems are modelled and solved by means of interacting electromagnetic "bricks". We propose an extension of LEGO able to handle bodies with anisotropic constitutive parameters and metallic objects (e.g., antennas). Since the anisotropic objects are dealt with LEGO, and the metallic parts are treated with the electric field integral equation (EFIE), we refer to the overall approach as hybrid LEGO-EFIE. The characterization of an electromagnetic brick which embeds an anisotropic object requires solving a volume integral equation (VIE). Since this procedure is carried out for each brick independently, the LEGO approach per se is extremely advantageous over the direct solution of a global VIE for all the bodies at once. Nonetheless, we further mix the hybrid LEGO-EFIE approach with the eigencurrents expansion method in order to tackle relatively larger problems. The technique is used to analyze a reconfigurable plasma antenna array (PAA) comprised of magnetized-plasma tubes placed around a two-dipole antenna array

ADAMANT : a surface and volume integral-equation solver for the analysis and design of helicon plasma sources

We present a full-wave numerical tool, dubbed ADAMANT (Advanced coDe for Anisotropic Media and ANTennas), devised for the analysis and design of radiofrequency antennas which drive the discharge in helicon plasma sources. ADAMANT relies on a set of coupled surface and volume integral equations in which the unknowns are the surface electric current density on the antenna conductors and the volume polarization current within the plasma. The latter can be inhomogeneous and anisotropic whereas the antenna can have arbitrary shape. The set of integral equations is solved numerically through the Method of Moments with sub-sectional surface and volume vector basis functions. This approach allows the accurate evaluation of the current distribution on the antenna and in the plasma as well as the antenna input impedance, a parameter crucial for the design of the feeding and matching network. We report several numerical examples which serve to validate ADAMANT against other well-established numerical approaches as well as experimental data. The numerical accuracy of the computed solution versus the number of basis functions in the plasma is also assessed. Finally, we employ ADAMANT to characterize the antenna of a real-life helicon plasma source