This letter focuses on 13.56 MHz high-frequency radio frequency identification (RFID) in the case of small tags detection, with an effective area below 1 cm 2. In such an identification system, based on load modulation principle, the magnetic coupling coefficient k and quality factor of the RFID reader coil are the key parameters. The main goal of this letter is to improve the detection of small tags over a given surface of 10 × 10 cm 2 by modifying the reader coil structure, and consequently the coupling coefficient k. Several coil designs are compared experimentally by distributing the diameters of their turns among three possible values. The design of the coils is based on empirical formulas that are in good agreement with experimental measurements. Electromagnetic simulations are performed to confirm the magnetic field distribution of the different designs. The results show that distributed diameter coil (DDC) as RFID reader coil is clearly efficient in this context of the RFID detection. The DDC structures determine the k factor, and, as k is low, the quality factor Q is a second parameter that can improve, in a second step, the RFID detection performances in function of the tag position and orientation.

This paper concerns a ground penetrating radar system (GPR) presenting beam forming ability. This ability is due to a great flexibility in the emission of wavefronts. The innovative concept is to use an array of antennas which can reconfigure itself dynamically, in order to focus on a desired target. This antennas system can act as a new microwave sensor to detect and characterize buried targets in an inhomogeneous medium which is the case study in various application fields such as geophysics, medical, planetology,… Its electronics are in development with the DORT (Time reversal technique) method integration for optimizing the localization of buried target. This paper aims are to present the antenna optimization used in the GPR applications. Typical antennas used in GPR are generally Vivaldi ones directly on the ground. Especially, in the context of the space mission ExoMars 2020, the radar antenna is set on a mobile station at a distance of about 30 cm from the ground to avoid any contact. However, they are limited by their important size, due to the lowest frequency of their bandwidth. Results of this work concern an increase of the antenna bandwidth by shifting the lowerband limit, making it a UWB type without changing its size. As low frequency waves can spread deeper into probed medium, this optimization can improve the radar data inversion performances.

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International audienceThe WISDOM (500MHz - 3GHz) GPR is one of the instruments that have been selected as part of the Pasteur payload of ESA's 2018 ExoMars Rover mission. One of the main scientific objectives of the mission is to characterize the nature of the shallow sub-surface on Mars and WISDOM has been designed to explore the first ∼ 3 meters of the sub-surface with a vertical resolution of a few centimetres. In order to illustrate and quantify the WISDOM performance, measurements in cold artificial and controlled conditions have been performed by the prototype. The objectives of this experiment were the detection of home made internal layering and the possible detection of a wedge included in the permafrost filled with different material with known characteristics. Some results and comparisons with a simple simulation are presented here and show the WISDOM performances

This paper proposes an HF (High Frequency) transmitting coil less sensitive to the angular and position misalignments of the small receiving coil. The DDC (Distributed Diameter Coil) shape and TLA (Twisted Loop Antenna) allow respectively minimizing the disturbance of the magnetic link due to the lateral misalignment and the relative tilting direction of the transmitting coil to the receiving coil. The magnetic coupling link obtained from DDC TLA coils is illustrated by comparison with conventional TLA in the case of HF RFID.