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International audience; In this paper, a rectangular slotted waveguide array is proposed for high power microwave applications. The antenna has been designed in the context of implementing a nonlethal high power transmission device onboard a drone to stop and neutralize non-cooperative vehicles. The proposed antenna comprises 16 slotted waveguides and a beamforming network, which is folded to maximize the compactness of the antenna. It has been specifically designed to send maximum EM energy in the range 20°-30° off-axis direction to avoid undesired ground reflections during operations. It has the ability to withstand a peak power of 500 kW. A measured gain of 27.7 dBi has been obtained at 3.15 GHz. The antenna has been successfully used to stop a car engine from a distance of approximately 9 meters.

International audience; In this paper, a detailed study and the optimization of a Negative Impedance Converter (NIC) circuit are presented to increase the bandwidth of a passive metasurface. The design and optimization procedure take into account the biasing and the effect of the transistors. The optimization ensures that the load can be realized with passive components.

International audience; This paper presents a metasurface reflector, characterized with a 0° reflection phase, which can be tuned to operate at any frequency within the band [1.1 – 1.7 GHz] and in two orthogonal polarizations independently. The proposed metasurface, based on a double layer of periodic metallic patches and varactors, behaves like an artificial magnetic conductor (AMC). By varying the capacitance values of the varactors, the positions of the resonant frequencies of the AMC can be tuned in real time. The proposed solution offers the possibility to overcome the narrow band characteristics of AMC structures and to control the two orthogonal polarizations independently.

The radiation of a series gap in a coplanar waveguide (CPW) line has been studied for Ku band applications. While theoretical models usually describe accurately the capacitance of the gap, they fail to include the radiation loss. This paper shows that it is a relevant phenomenon in Ku Band when the width of the line is close to 1mm and low precision etching is employed (low cost printing technology). Additionally, a technique for the reduction of such losses is presented and evaluated.

In this paper, the electromagnetic properties of two difier- ent High Impedance Surfaces (HIS) with or without Electromagnetic Band Gap (EBG) in difierent conflgurations are investigated for mutual coupling reduction in small antenna arrays. The resonant mechanisms of these structures are studied using transmission calculations in a par- allel plate waveguide. An optimum conflguration is then proposed. It is shown that a good isolation performance can be achieved without the need of metallic vias when the structure is embedded in a metal- lic cavity, which limits signiflcantly the number of HIS cells needed to perform a good isolation and the cost of manufacture.

This paper presents an anti-jam GPS array. The antenna is comprised of 4 small size radiating cavities filled with two stacked patches and a series of dielectric substrates and a foam layer. The main features of the antenna are low profile shape and low inter-element coupling. The antenna design is compatible with high impedance surface (HIS) insertion, which can potentially improve the anti-jam capabilities of the array by providing further inter-element coupling reduction.

In this article, HIS-like resonators are proposed for mutual coupling reduction between the elements of a small array. First, a methodology is proposed for the design of HIS-like resonators. Then, a reference array made of two cavity backed patches working in L-band is designed. HIS-like resonators are then introduced in the array in order to reduce couplings between the patches in E-plane configuration. These two arrays are then manufactured with modular parts, providing the possibility to replace the patches and tune the HIS-like resonators resonant frequency. Simulated and measured S-parameters are illustrated, showing the capability of these structures to reduce significantly mutual couplings.

An original method of characterization of high impedance surfaces (HIS) is presented to exhibit electric field patterns. The electric field frames are obtained through a resistive film located in the near field domain of the HIS. The film heating is recorded using an infrared camera and gives after post-processing electric field magnitude profiles. We applied this technique to a HIS specially tuned for reducing mutual coupling in a global navigation satellite systems (GNSS) array designed for the E5 Galileo band. The mushroom-like HIS, designed and realized with the help of simulation, is located near the ground plane of a micro-strip line which allows S parameter characterization. Present measurement enables near field characterization and field structure analysis, and is therefore a complement to usual analysis. Moreover, the technique shows the very special field structure, including sub-lambda details, created by the HIS and more generally by metamaterial structures.

We propose a web-based collaborative CAD system allowing for the remote communication and data exchange between radiologists and researchers in computer vision-based software engineering. The proposed web-based interface is implemented in the Java Advanced Imaging Application Programming Interface. The different modules of the interface allow for 3D and 2D data visualization, as well as for the parametric adjustment of 3D reconstruction process. The proposed web-based CAD system was tested in a pilot study involving a limited number of liver cancer cases. The successful system validation in the feasibility stage will lead to an extended clinical study on CT and MR image databases.

A novel hybrid method based on plane wave spectra interactions has been presented for field calculation of GPR antenna patterns. The method has been employed for two validation cases involving a dipole and a TEM horn antenna. This method offers the possibility to investigate the performance of a wide range of complex antennas operating in the presence of the ground at standoff distances. The advantage of the method is that, it substantially reduces the computational resources needed and additionally, it offers the possibility of selecting the best method for the analysis of the antenna and the ground sub-domains. The analysis of the ground sub-domain leads to a database for the response of the soil plus the target. Using these data, the performance of a complex antenna positioned at any desired distance or orientation relative to the ground, can be modelled and optimised with minimal computational impact.

Much attention is being given to the challenge of detecting buried non-metallic mines and National and International programs are underway to develop more effective detection and clearance systems. Conventional metal detectors respond to the metal content of a mine, hence the minimum metal or plastic mine remains largely undetectable by current technology, particularly in areas where battlefield debris and shrapnel cause a high false alarm rate. Ground Probing Radar (GPR) offers useful performance improvements in these situations and used in conjunction with metal detector arrays can result in an improved fused performance in terms of increased signal to clutter ratio. This paper considers several aspects of the performance of GPR systems, in particular the antenna elements and arrays of antennas. Examples of the radar images of mines and the factors that influence image quality are presented.