This paper presents microwave tomographic reconstructions of the complex permittivity of lossy dielectric objects immersed in water from experimental multiview near-field data obtained with a 2.45-GHz planar active microwave camera. An iterative reconstruction algorithm based on the Levenberg-Marquardt method was used to solve the nonlinear matrix equation which results when applying a moment method to the electric field integral representation. The effects of uncertainties in experimental parameters such as the exterior medium complex permittivity, the imaging system geometry and the incident field at the object location are illustrated by means of reconstructions from synthetic data. It appears that the uncertainties in the incident field have the strongest impact on the reconstructions. A receiver calibration procedure has been implemented and some ways to access to the incident field at the object location have been assessed.

The paper is focused on the characterization of objects immersed in water using laboratory-controlled data obtained in the microwave frequency range. Experiments performed at the laboratory represent, at a reduced scale, the electromagnetic characterization of objects buried at a shallow depth in the sea, with the objects and the emitting and receiving antennas being immersed. Characterization is taken here as an inverse scattering problem whose data, whilst limited in aspect, consist of the values of the time-harmonic scattered electric fields measured at several discrete frequencies on a single line of a few receivers. The modelling of the wave-object interaction is performed through a domain integral representation of the fields in a two-dimensional transversemagnetic configuration. The inverse scattering problem is solved by means of two iterative algorithms tailored for homogeneous objects: the so-called level-set method and a binary specialized contrast source inversion method. Emphasis is put both on the experimental features and their modelling, and the results obtained for different types of objects are presented.

We are concerned, herein, with the conception and the design of printed UWB antennas and with the analysis of their performances through figures of merit. State of the art gives the opportunity to exploit some empirical considerations about the shape and the methodology of conception. A simple structure is simulated by means of CST Microwave Studio to show the possibility of fulfilling, at a defined level, UWB antenna requirements such as matching, fidelity and quasi-isotropy of the radiation pattern with a simple micro-strip design and a standard technology.

International audienceThis paper summarizes some tests with Low Frequency (LF, 125 kHz) RFID tags of two types: Card and Token. These tests were done in order to evaluate the feasibility of an identification/traceability of tags which size is constrained and supposed to be detected inside a delimited volume of 40x40x10 cm3. As the size of the antenna tag is supposed to be very small, we improve the detection range and volume of definition by designing different reader antennas. Reader antennas presented are of two types whether they are based on single (SL) or multiple loops (ML). Detection range was evaluated for planar antennas (3 SL and one ML). Volume of definition for the detection was estimated by designing two-level prototypes of ML antennas. Results are discussed about the optimization possibility of detection range and volume thanks to M