Marc Thevenot

Directive photonic-bandgap antennas

This paper introduces two new photonic bandgap (PBG) material applications for antennas, in which a photonic parabolic reflector is studied. It is composed of dielectric parabolic layers associated to obtain a PBG material. The frequency gap is used to reflect and focus the electromagnetic waves. This device has been designed using a finite-difference time-domain (FDTD) code. FDTD computations have provided the theoretical reflectors directivity. These results are in good agreement with measurements, and it appears that the PBG reflector presents the same directivity as a metallic parabola. A second application uses a defect PBG material mode associated with a metallic plate to increase the directivity of a patch antenna. We explain the design of such a device and propose experimental results to validate the theoretical analysis.

An electromagnetic bandgap resonator antenna

This paper introduces a new explanation of the electromagnetic bandgap (EBG) material properties using the study of the EBG structures in the frequency domain and reciprocal space. Once the behavior of such a material is understood, the properties of the EBG are used in order to make an EBG antenna. The antenna is realized with dielectric EBG rods. Its directivity is increased compared to a simple patch antenna. Such a device allows us to obtain a high gain with a very thin structure.

Circularly polarized metallic EBG antenna

This letter describes the concept and the realization of a directive and circularly polarized antenna using an electromagnetic band gap material whose circular polarization is generated by the structure itself. Experimental and simulated results are presented for an antenna operating at 5GHz.

Mutual Synthesis of Combined Microwave Circuits Applied to the Design of a Filter-Antenna Subsystem

A mutual-synthesis approach is presented for the design of subsystems combining two microwave circuits. In this paper, we are focused on subsystems combining a filter and an antenna. In a first step, the methodology consists of synthesizing the global subsystem, which realizes both filtering and radiation functions, with respect to overall specifications. Considering circuits interactions within the subsystem, the resulting constraints are distributed optimally between the two circuits. The latter mutual synthesis then leads, on one hand, to a set of optimal impedances for their connection and, on the other hand, to the corresponding ideal characteristics of each circuit. A solution can then be selected by carrying out a compromise between the simplicity of achieving the characteristics of each circuit and the performances and compactness of the subsystem. In a second step, the circuits are designed independently with respect to the synthesized characteristics. Compared to a classical synthesis approach, where circuits are synthesized independently with respect to a common reference impedance (generally 50 or 75 Omega), the proposed mutual synthesis allows to simplify the global subsystem since interactions between the two circuits are considered and used optimally. The technique is illustrated with the design of a filter-antenna at Ku-band.

Global Design of an EBG Antenna and Meander-Line Polarizer for Circular Polarization

This letter describes a comprehensive approach to design circularly polarized electromagnetic band-gap(EBG) antennas. Some solutions have already been proposed to that end, but they require the design to be started from scratch. With the proposed method, the circular polarization will be obtained through the use of a meander-line polarizer (MLP) located above an existing linearly polarized EBG antenna. Thanks to a global approach, a 20-dBi circularly polarized antenna, boasting an axial ratio (AR) lower than 1 dB over the 29.530 GHz frequency band, has been conceived, realized, and successfully measured.

Investigations of the Effects of Mutual Coupling in Reflectarray Antennas

In this paper, we investigate the effects of mutual coupling in reflectarray antennas because this remains one of the most critical points in reflectarray design. By including the scattering-matrix effect in the synthesis procedure, we demonstrate that the mutual coupling between the cells affects not only the reradiated phases, but also the magnitude of the reradiated waves, which is the originality of the paper. This paper highlights the interactions between the cells, leading to a better understanding of the radiation patterns behavior. A full-wave simulation is used to successfully validate the synthesis procedure and the effects of mutual coupling. The presented approach is currently confined to the case of identical cells with reactive loads as phase-compensation elements.

Efficient design of rectifying antennas for low power detection

This article is dedicated to the design of rectifying antenna for wireless energy transfer at 2.45 GHz in the special case of low input power (typically <−10 dBm). As the rectifiers present an important non-linear behavior with such power levels, specific design guidelines must be respected in order to optimize the structure. Different rectifying circuits have been studied and their performances have been evaluated through the definition of a Figure of Merit. The effects of the antenna impedance have also been investigated to improve the performances. Two test-circuits have been manufactured and measured to validate the simulation results and to confirm the interest of a global design approach with such rectifying structures.

Phase Center Study of the Electromagnetic Band Gap Antenna: Application to Reflector Antennas

Recent studies have shown that the electromagnetic band gap (EBG) antenna can be used to feed a reflector, especially to realize multibeam coverage with geostationary satellite. However, it is necessary to evaluate its performances in terms of aperture efficiency to compare this solution to the classical ones. Among all the parameters which contribute to the aperture efficiency, one of the most important is the phase center, which has never been determined for EBG antennas. This is the aim of this letter. After defining a simple method to calculate the phase center of the EBG antennas, the position and the frequency evolution of this parameter will be studied. Then, the performances of such a feed associated with a Side Fed Offset Cassegrain Antenna (SFOCA) will be evaluated and compared with a classical feed for reflector, a Potter horn

Interlaced feeds design for a multibeam reflector antenna using a 1-D dielectric PBG resonator

The 1-D dielectric resonator PBG allows to generate directive and interlaced reflector feeds in order to obtain optimal focal fed antenna efficiency and closely spaced beams. Our passive system is supposed to replace the complex, active and heavy reflector feeds.

1D dielectric electromagnetic band gap (EBG) resonator antenna design

This article presents a new methodology allowing to design a planar electromagnetic band-pap antenna (choice of theebg material, sizing, feeding). This kind of antenna has already been presented.ebg antennas are very thin (compared with parabolic reflectors) high gain antennas. This article makes easier the realization ofebg antennas whatever the operating frequency, the gain, or still the bandwidth. A study about the sensitivity of the material properties on the performances is also presented. Finaly two exemples using this design method are described.RésuméCet article décrit une méthodologie complète inédite permettant de dimensionner et de réaliser une antenne planaire à bande interdite électromagnétique (Choix du matériau, de la configuration, dimensionnement, alimentation...). Le fonctionnement de ce type d’antenne a déjà été publié. Les antennesbie sont des antennes directives à encombrement réduit en épaisseur (En comparaison avec par exemple une antenne parabolique). Cet article facilite la réalisation des antennesbie quelques soient la fréquence, le gain ou encore la bande de fonctionnement. Une partie concerne également la sensibilité des éléments du matériau sur les performances de l’antenne. Enfin, deux exemples concrets utilisant cette méthode de conception sont présentés.