1— In this paper we describe the design of shaped dielectric dome antennas radiating a secant-squared beam at 60GHz. The design methodology consists in a binary Genetic Algorithm combined with an asymptotic method of analysis based on the Geometrical Optics / Physical Optics technique. The dome antenna is made in Rexolite and is excited by a compact pyramidal horn antenna. The use of matching layers coated on both sides of the dome enables one to reach a 5GHz band around the central frequency.

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, epsivr=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.

This article reports experimental results on the influence of low-power millimeter wave (MMW) radiation at 60 GHz on a set of stress-sensitive gene expression of molecular chaperones, namely clusterin (CLU) and HSP70, in a human brain cell line. Selection of the exposure frequency is determined by its near-future applications for the new broadband civil wireless communication systems including wireless local area networks (WLAN) for domestic and professional uses. Frequencies around 60 GHz are strongly attenuated in the earth's atmosphere and such radiations represent a new environmental factor. An exposure system operating in V-band (50-75 GHz) was developed for cell exposure. U-251 MG glial cell line was sham-exposed or exposed to MMW radiation for different durations (1-33 h) and two different power densities (5.4 microW/cm(2) or 0.54 mW/cm(2)). As gene expression is a multiple-step process, we analyzed chaperone proteins induction at different levels. First, using luciferase reporter gene, we investigated potential effect of MMWs on the activation of transcription factors (TFs) and gene promoter activity. Next, using RT-PCR and Western blot assays, we verified whether MMW exposure could alter RNA accumulation, translation, or protein stability. Experimental data demonstrated the absence of significant modifications in gene transcription, mRNA, and protein amount for the considered stress-sensitive genes for the exposure durations and power densities investigated. The main results of this study suggest that low-power 60 GHz radiation does not modify stress-sensitive gene expression of chaperone proteins.

A computer-aided design (CAD) tool is proposed for the analysis and optimization of multi-shell Integrated Lens Antennas (ILAs) of arbitrary three-dimensional (3-D) shape and dielectric constitution. The analysis of the lens performance is carried out using the conventional hybrid geometrical / physical optics (GO/PO) method. The optimization of the lens shape is based on a binary genetic algorithm (GA) coupled to the GO/PO kernel. The ILAs considered here are single- and double-shell lenses of arbitrary shape. Two designs of single-shell lenses made in Rexolite and ceramic materials are presented and compared for non axis-symmetric Gaussian far-field specifications. The drawbacks of single-shell geometries are highlighted, and a double-shell ILA is designed in order to maximize the power transfer efficiency of the antenna. These results demonstrate that double-shell configurations can improve significantly the performance of ILAs of moderate size.

This paper presents the theoretical performance (input impedance, -10 dB return-loss bandwidth, radiation patterns and surface efficiencies) of reduced size substrate lenses fed by aperture-coupled microstrip patch antennas. The diameter of the extended hemispherical homogeneous dielectric (/spl epsiv//sub r,lens/) lenses varies between one and five wavelengths in free-space, in order to obtain radiating structures whose directivity is comprised between 10 and 25 dB. A lot of configurations of lenses are investigated using the finite-difference time-domain methods technique and compared in the 47-50 GHz band as a function of their diameter, extension length and dielectric constant. In particular, the analysis of internal reflections-in time and frequency domains-shows that the latter have potentially a strong influence on the input impedance of small lens antennas, even for low values of /spl epsiv//sub r,lens/(2.2), whereas the usual limit (beyond which anti-reflection coatings are required) is /spl epsiv//sub r,lens/=4. We also demonstrate that the diffraction limit of reduced size lenses is reached for extension lengths varying between 50% and 175% of the extension of synthesized ellipses, depending on the lens material and diameter. Finally, we show that superdirective structures with surface efficiencies reaching 250% can be obtained with small lens diameters, justifying the interest in reduced size lens antennas.