J. Lanteri

Whole-microwave system modeling for brain imaging

In this paper, we present the results of a whole-system modeling of a microwave measurement prototype for brain imaging, consisting of 160 ceramic-loaded antennas working around 1 GHz. The modelization has been performed using open source FreeFem++ solver. Quantitative comparisons were performed using commercial software Ansys-HFSS and measurements. Coupling effects between antennas are studied with the empty system (without phantom) and simulations have been carried out with a fine numerical brain phantom model issued from scanner and MRI data for determining the sensitivity of the system in realistic configurations.

Quantitative millimeter-wave imaging in W-band

In this paper, we present quantitative image reconstructions (i.e. permittivity and conductivity profiles) from synthetic and experimental data. First, we perform the qualitative imaging for localizing the target in order to determine the investigation domain. Second, we solve the inverse-scattering problem via an iterative algorithm based on a Conjugate Gradient (CG) method.

Antenna measurement using cylindrical coefficients modes(CMCs) in non-anechoic environnement

This paper presents Exponential Tapered slot antenna (ETSA) radiation pattern measurement in Non Anechoic Environment. It suggests a method based on CMC decomposition and modal filtering in order to get rid of perturbations. First Cylindrical Near-field to Far-field Transformation and calculation of CMC are described. Then a simulation on an ETSA and a Perfect Electric Conductor (PEC) obstacle is done. Simulation results are presented for a frequency of 2 GHz. Far-field pattern cut at theta=90° is presented. Comparison between the simulated radiation pattern of ETSA without obstacle and the one of ETSA with PEC after filtering is proposed. A good agreement between these two curves is observed.

Millimeter-wave imaging of foreign object debris (FOD) based on two-dimensional approach

In this paper, we present the results of image reconstructions of foreign object debris (FOD) based on 2D algorithms in the W-band (75-110 GHz). To test the feasibility of using 2D reconstruction algorithms, we first studied the relevance of two-dimensional assumption in the working frequency band for different typical debris. Thanks to the short wavelength (2.7 to 4 mm), most debris can be considered as two-dimensional. The reconstruction of complex permittivity profile for dielectric (lossy or lossless) and perfectly conducting targets is carried out using 2D-TM and 2D-TE algorithms using characteristic elements (VV, VH, HV and HH) of the scattering matrix with polarimetric measurements in multistatic configuration.

Electronical beam scanning using integrated CMOS continuous 0°–360° phase shifter

A phase shifter designed in a 130 nm CMOS technology is presented. It consists of a variable gain amplifier in cascade with a 2.45 GHz LC differential quadrature oscillator and allows to get a continuous phase step from 0° to 360°. An application to dynamic beam scanning is presented and a 1° accuracy of the scanning angle is demonstrated for an 8×1 planar antenna array with phase control.

94 GHz printed reflectors using C-shape patches

Folded printed Fresnel zone plate reflector is presented for helicopter collision avoidance radar at 94 GHz. The achievement of a folded structure, requires printed elements that perform a 180deg phase difference of the reflected phase between two orthogonal polarizations. For this purpose, C-shape patches were designed. A prototype of 130 mm diameter was made and measured. The first section describes the reflector design with a focus on the C-shape patches mode of operation. The second part shows the concept validation by the mean of antennas radiation pattern measurements as well as in flight measurements of the antenna mounted on the detection radar.

Improvement of Reflectarray Performances at Millimeter Waves by Reduction of the Cell Size

In this paper we discuss the advantages and limitations of reducing the cell size of reflectarrays elements. Reflectarrays have demonstrated their utility at mm-Wave because of their compactness, flexibility and quasi-optical feed that reduces losses. Several applications have been covered such as the automotive cruise control including beam scanning. Most of them use λ/2 cell sizes. We have investigated and compared performances of reflectarrays with 15mm and 50mm diameters using λ/2 and λ/4 cell sizes at 94GHz. Measurements on reduced cell size reflectarrays have demonstrated a loss of 1 dB over 60◦ beam scanning whereas it is of 3 dB for the λ/2 structure in the case of the smaller reflector. Nevertheless, this effect is not demonstrated on the largest one because of the phase compensation range that is limited by the variation in the patch dimensions. The maximum corrected phase values are of 320◦ and 240◦ for λ/2 and λ/4 cells respectively. Furthermore a program based on the ray tracing theory has been developed in order to evaluate the influence of the cell size on the array performances.