Wide Band Antenna Array for Synthetic Aperture Radar Applications

Abstract or Introduction

In this thesis, a PSO optimization algorithm is applied using a developed technique to synthesize the radiation patterns required for high-resolution land imaging SAR and satellite communications using planar rectangular or concentric circular arrays. The goal of the PSO algorithm is to get the excitation coefficients of the array elements, which are, then, Microstrip patch antennas with linear or circular polarization are proposed to construct the synthesized-beam arrays required for the considered application.

A wide band rectangular patch antenna with U-slot is proposed for planar arrays with linear polarization. A square patch antenna with four truncated corners and four axial slots is designed for planar rectangular and circular arrays. Finally, a square patch antenna with two L-shaped slots inserted at diagonally opposite corners is designed for planar concentric circular arrays. Turnstile arrays of either dipole elements or U-slotted microstrip patch antennas excited with circulating phase shift are proposed to construct planar arrays with circular polarization for land-imaging SAR systems and satellite communications.

Synthetic Aperture Radar (SAR) is used for remote sensing to create two-dimensional images of land covers on the earth’s surface. Such a land-imaging system has a great importance in many civilian and military applications. The SAR uses the radar antenna to scan a ground area to provide microwave images with fine spatial resolution. The SAR is typically mounted on an aircraft or spacecraft, and usually has a form of side-looking radar. It uses the Doppler and time delay information of the ground reflected wave to generate a two-dimensional image with the desired azimuth resolution (direction of motion) and range resolution (normal to the direction of motion), respectively.

The SAR operation requires a physical antenna of radiation pattern with foot print of high aspect ratio and a mechanism capable of achieving beam steering and beam shaping. The SAR antenna array should be rigid, planar, deployable, and as lightweight as possible. A side-looking SAR system requires an antenna with a flat-topped beam pattern in the plane of the azimuth direction and a cosecant-squared beam shape in the plane of the range direction. For satellite communications with the ground stations, an isoflux beam is required for uniform coverage and continuity during the communication session.