Christophe Conessa

Quantitative Microwave Imaging for Breast Cancer Detection Using a Planar 2.45 GHz System

Microwave imaging is recognized as a potential candidate for biomedical applications, such as breast tumor detection. In this context, the capability of a planar microwave camera to produce quantitative imaging of high-contrast inhomogeneous objects is investigated. The image reconstruction is achieved by means of an iterative Newton-Kantorovich algorithm. Promising numerical simulation results indicate that the planar geometry is suitable for quantitative imaging, as long as the signal-to-noise ratio is higher than 40 dB. Such a requirement is satisfied with the camera due to appropriate data averaging. Furthermore, different calibration techniques are discussed, aiming to reduce the model error, which results from the limitations of the numerical model involved in the reconstruction to accurately reproduce the experimental setup. The experimental work also includes the development of a phantom using a new fluid tissue equivalent mixture based on Triton X-100. As a final result, this paper shows the first reconstructed quantitative images of a high-contrast inhomogeneous 2-D object obtained by using experimental data from the camera.

Breast Phantoms for Microwave Imaging

Herein, we study the dielectric properties of various mixtures susceptible to be used in manufacturing of reference inhomogeneous breast phantoms dedicated to the experimental validation of microwave breast imaging systems in the 0.5-6-GHz frequency range. Particularly, we investigate the stability over time and temperature of these properties and their reproducibility for a given mixture, as well as the ability of some mixtures to mimic the various breast tissues, i.e., to show dielectric properties close to that given by one-pole Debye models that describe the mean relative dielectric permittivity of various tissue types.

Towards a planar Microwave Tomography system for early stage breast cancer detection

In this paper, the advantages of planar Microwave Tomography (MT) applied to early stage breast cancer detection are presented. In the proposed planar configuration, the breast is compressed between two dielectric plates in a configuration similar to that of X-ray mammography. This approach would allow the future implementation of a dual modality imaging system where the advantages of both techniques can be exploited. The research efforts made both at DRÉ/L2S (Supelec) and Poly-grames (École Polytechnique de Montréal), for the development of a planar MT system are described, as well as, the key features of the latter. A numerical validation is used to show how the breast compression can lead to an enhancement of the reconstructed images.

Improvement of HF RFID Tag Detection With a Distributed Diameter Reader Coil

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 cm2. 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 cm2 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.

Improving LF reader antenna volume of detection for RFID token tag thanks to Identical Coaxial Loops (ICLs) and in/out-of phase multiple-loops structures

This work concerns the prototyping of a low cost PCB based multiple loops antenna for LF 125 kHz RFID application. The multiple loops structure is considered for the context of small tags traceability, for example token tags such as circular HitagS (1-2 cm of diameter). The targeted volume is 20×20×10 cm3 for the moment. The position of the tag can be parallel or orthogonal to the reader antenna plane, with a variation of the angle position, and is moving inside the volume of detection (small objects in a storage basket in practice). The dedicated conception of a reader antenna is necessary because the application targets a volume of detection rather than maximum range detection. Additionally, the position of the tag is not known. The design considerations are based on a combination of Identical Coaxial Loops (ICL) and in/out-of phase loops structures whose advantages are discussed in terms of mutual inductance in the simulation part. An optimum diameter of 7,5 cm is noticed for square loops case. The realization of this structure shows qualitatively good results for our objectives and emphasizes a tradeoff between the two effects of coupling due to the two structures combined. As the tag is moving inside the volume, with an orientation (tag position test) unknown, our observations drive to the conclusion that the detection will be effective. Some perspectives are also clearly identified to improve the structure in the future.

Detecting range and coupling coefficient tradeoff with a multiple loops reader antenna for small size RFID LF tags

This 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 40×40×10 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 ML.

Sub-coil in reader antenna for HF RFID volume detection improvment

This paper proposes a reader antenna, improving the inductive coupling with a small coil whatever its position or orientation against the reader antenna. Sub-coils are inserted and the turn number is optimized in order to improve efficiency of the inductive coupling in the case of HF RFID volume detection in keeping constant the magnetic energy generated by the reader.

Design of 1cm 2 coils for HF RFID instruments tracking with detection range improvement

This paper concerns an application of magnetic coupling RFID technology at 13.56 MHz (HF band) for tracking devices such as instruments. The tag size is defined to be ergonomically small compared to the hand, and fixed inside a maximum surface of 1 cm2. The case of multiple detections is considered, and consequently the reader surface of control is considered wide enough to include several instruments at the same time during a logistic control process. The use of such a small RFID tag is almost impossible using a large reader loop of 15×30 cm2, as chosen for the tests. The key idea of the paper is then the addition of a resonator that enables to create the mandatory physical link by means of magnetic coupling between the tag coil and the resonator coil and between the resonator coil and the reader loop. Finally the detection range is highly improved by the presence of this resonator and results demonstrate that it is possible to detect these small RFID “1 by 1 cm2 tags” at a distance of 1.5 cm to 3 cm, depending on their orientations.

Distributed Diameter sub-Coil Twisted Loop Antenna in non-radiative WPT

This letter focuses on the high-frequency wireless power transfer by electromagnetic induction and its dependence on the lateral misalignment and tilt of the small receiving coil relative to the transmitting coil. We combine two structures, the twisted loop antenna (TLA) and subcoils of a distributed diameter coil (DDC) for transmitting designs. Our system is then referred to as TLA-DDC. The radius of the subcoils is parametrically varied for different distances between the coils and performed in two positions for each distance (coaxial position when the receiving coil is parallel to the plane of the transmitting coil, and center position for the perpendicular orientation of both coils). Then, using different radii for the transmitting DDC TLA when the receiving coil is moved onto its surface allows us to obtain a greater value of efficiency at different positions: up to 2.4 times for the peak value and 1.5 for the average value for receiving coil in parallel plane. The efficiency of the magnetic coupling is determined by means of power efficiency with a comparison between the DDC TLA antennas and a standard coil antenna corresponding to the same inductance value.

Reader antenna including resonators for HF RFID detection

In this article, HF RFID reader antenna including small resonant coil, operating with the magnetic coupling with the reader coil, is reported. The proposed system is used to improve surface and volume of small tag detection. The performances of such system are validated by maximization of input impedance (load modulation principle) and equivalent mutual inductance between the reader dual-coils and the tag coil compared to a conventional RFID reader antenna. Analytical formulas of theses parameters are developed. The proposed system is validated by detection measurements in parallel and perpendicular configurations between the reader and the tag coils.