Caractérisation d’une antenne microbande couplée par une ouverture de forme rectangulaire.Application à la réalisation d’une antenne multibande.

Abstract

The main purpose of this thesis was to study, modeling and design of printed antennas. Three main parts have formed the body of this thesis. In the first part, we have developed two methods for modeling a rectangular microstrip antenna with a rectangular aperture in the ground plane. The first method is based on the determination of hybrid dyadic Green’s functions in the spectral domain, while in the second method, we have applied the finite difference time domain for the analysis of the microstrip antenna. The two methods have been validated by comparing our numerical results with experimental measurements as well as with results obtained using the HFSS simulation software. The second part has been devoted to the study of performances of two multi-antennas systems. Each system has eight radiating elements having as a basic element a microstrip patch. The main difference between these two systems lies in the excitation technique, where the radiating elements of the second multi-antenna system have been fed through apertures cut into the ground plane. The performances in terms of adaptation and isolation for these two systems have been discussed. Results concerning the radiation patterns and gain have been also presented. In the third part of this thesis, our efforts were directed towards the design of a new tri-band triangular monopole antenna structure. A rectangle-shaped aperture has been etched on the radiating element to generate the second resonant frequency. To obtain the third resonant frequency, a pair of symmetrical L-shaped parasitic elements has been added on both sides of the triangular monopole antenna. A coplanar waveguide feeding mechanism has been used to provide good performances on all bands. The CST simulation software has been used in the optimization of the parameters of the proposed antenna. A prototype of the proposed antenna has been fabricated in the RF laboratory of the INRS in Montreal, Canada. The simulated results in terms of reflection coefficient and radiation pattern have been compared with experimental measurements and a good agreement has been obtained. Measured and simulated results demonstrate that the proposed antenna can achieve three desired operating bands, higher isolation characteristic between adjacent bands. A stable gain and a good omnidirectional radiation in the H-plane have also been achieved. As a result, the performances offered by the proposed antenna are very promising for practical WLAN/WiMAX applications.