Amélioration des caractéristiques des patchs microbandes pour les applications ultra large bande.

Abstract

The thesis work aims to design wideband planar circularly polarized patch antennas with high radiation stability in a large scale of simplicity and repeatability in terms of frequency. The first proposed geometry is a broadband circularly polarized CPW-fed slot patch antenna. This latter consists of two unequal L-shaped arms, feeding asymmetricallyshaped slot at two opposite corners to achieve wider circularly polarized bandwidth in stable radiation, without any external polariser. The antenna performance exhibits a wide 3–dB axial ratio bandwidth (3–dB ARBW) of 2.8 GHz; starting from 7.4 GHz until 10.2 GHz, within the 10–dB impedance bandwidth (10–dB IBW) of 3.2 GHz (7–10.2 GHz). Results show a stable radiation in the broadside direction, in which the antenna shows a maximum gain of 4 dBi in bidirectional broadside radiation. The measurement results show very good concordance with those of simulation. The second proposed antenna is a circularly polarized spirally shaped patch antenna, covering an ultra wide frequency band. A wide 3–dB axial ratio bandwidth (3–dB ARBW) of 2.53 GHz is obtained; starting from 7.91 GHz up to 10.44 GHz, within a 10–dB impedance bandwidth (10–dB IBW) of 7.5 GHz, covering the frequency range of 4.5 GHz to 12 GHz with a high stability in the main beam direction of θ = 20◦, ϕ = 135◦. As well as, a high peak gain of 8.85 dBi is reached at 10.2 GHz within the operating frequency range. Compared to many works in the literature, the proposed antennas then have the advantages of being simple planar, having wide CP bands and they radiate efficiently in high stability in terms of the direction of the main lobe.