Design of Dielectric Dome Antennas with Shaped and Pencil Beams at Millimeter Waves

The aim of this paper is to contribute to the determination of the potentialities of dielectric dome antennas for shaped beam applications at millimetre waves. To this end, the shapes of the dielectric interfaces of the dome are optimized so that its far-field radiation patterns comply with desired specifications. Our synthesis methodology combines a binary Genetic Algorithm (GA) and an asymptotic method of analysis based on the Geometrical Optics / Physical Optics (GO/PO) technique. This CAD tools allows modelling multi-shell / multi-material dielectric dome antennas of arbitrary shapes. Its main capabilities are firstly described (flow chart, representation of the dielectric interfaces, binary differential coding, convergence of the algorithm, etc.). Then two dome antennas are designed at 60 GHz. Both of them are made of a low-k material (namely Rexolite, ε_r=2.53). The first antenna prototype radiates an axis-symmetric secant-squared beam for high speed indoor communication systems in V-band. The second dome antenna radiates a circularly-symmetric Gaussian-like beam. In contrast to the first prototype, the dome shape and the feed dimensions have been optimised simultaneously. This design strategy enables one to improve significantly the radiation performance of the dome. Experimental results are in good agreement with the numerical results. The impact of the multiple internal reflections is also highlighted.