M'Hamed Drissi

Optimization of Reduced-Size Smooth-Walled Conical Horns Using BoR-FDTD and Genetic Algorithm

An accurate optimization tool has been developed to design arbitrarily-shaped axis-symmetrical devices. It is based on the combination between a genetic algorithm (GA) and a finite-difference time-domain (FDTD) solver formulated in a cylindrical coordinate system. For validation purposes, this tool is applied to design several smooth-walled compact conical horns with a large flare angle (90°) in the 60-GHz band. The unavoidable phase distortions appearing in the horn aperture are compensated by loading the horn mouth with thin shaped dielectric lenses made in Rexolite. Based on these test cases, several synthesis strategies are discussed and compared in order to select the best antenna prototype among those synthesized. A scaled version of this prototype has been fabricated to operate around 29.5 GHz. The numerical and experimental results are in excellent agreement. Horn size reduction rates up to 80% have been reached.

Size reduction of dielectric-loaded horn antennas combining a Body-of-Revolution (BoR) - FDTD solver and a Genetic Algorithm (GA)

This paper presents an electromagnetic synthesis tool for the design of axis-symmetrical radiating structures has been described. It is based on the combination of a fast BoR-FDTD solver coupled to a real-coded GA. To reduce the computation time, grid-computing techniques have been applied. The implementation has been validated through the synthesis of conical horn antennas loaded with shaped lenses at 60GHz. The proposed designs have shown that a 60% size reduction can be achieved. Experimental results will be presented during the Conference.

Synthesis of small axis-symmetrical shaped integrated lens antennas: Comparison between full-wave and high-frequency optimization strategies

A CAD tool based on real-coded GA and BoR-FDTD has been implemented for the synthesis of axis-symmetrical radiating structures of moderate size. It has been validated numerically via the optimization of small-size single-shell integrated lens antennas (ILAs) fed by dielectric-loaded circular waveguide. It has been shown that shaping the lens surface using BoR-FDTD enables one to enhance the peak directivity compared to the GO predictions. Comparison with the performance of two lens prototypes synthesized with our BoR-FDTD/GA and GO / PO-GA tools has highlighted the limitations of the GO / PO approach.

Printed bowtie antenna fed by electromagnetic coupling

Printed planar antennas are widely used in many current applications. One of the main limitations is their narrow bandwidth. To improve this last parameter, several shapes have been studied, namely: bowtie, spiral, logarithmic antennas, ... The investigated results indicate that the radiating performances are influenced, as expected, by the dielectric substrate, the radiating element shape and the feeding circuits. In the present research, printed bowtie antennas fed by electromagnetic coupling from an embedded microstrip line are investigated, An impedance transformer circuit is optimized and the obtained performances are compared to those given by a simple 50 /spl Omega/ microstrip line. Measurements of return loss and radiation patterns are also presented and compared to the calculated ones.

Compact shaped horn antennas in metallized foam technology

We describe in this paper the synthesis of directive axis-symmetrical compact shaped horn antennas. The proposed CAD tool is based on the combination between a FDTD solver in cylindrical coordinates and a genetic algorithm. A low-cost fabrication technique using a metallized foam 3-D technology is employed for experimental validations in Ka-band. The measurement results are in excellent agreement with the numerical predictions. Radiation efficiencies up to 89% have been obtained at 29.5 GHz.