Super-gain miniature antennas with circular polarization and electronic beam steering
Antenna radiation control in terms of shape and polarization is a key element for future communication systems. Directive compact antennas offer new opportunities for wireless applications in terms of spatial selectivity and filtering. This leads to a reduction in electromagnetic pollution by mitigating interferences with other communication systems and reducing battery consumption in compact smart devices (IoT), while enabling also new use modes. However, the conventional techniques for enhancing the directivity often lead to a significant increase of the antenna size. Consequently, the integration of directional antennas in small wireless devices is limited. This difficulty is particularly critical for the frequency bands below 3 GHz if object dimensions are limited to a few centimeters. Super directive/gain compact antennas with beam-steering capabilities and operating on a wideband or on multi-bands are an innovative and attractive solution for the development of new applications in the field of the connected objects. In fact, the possibility to control electronically the antenna radiation properties is an important characteristic for the development of the future generation and smart communication systems. CEA Leti has a very strong expertise in the domain of superdirective antennas demonstrating the potentials of the use of ultra-compact parasitic antenna arrays. This PhD project will take place at CEA Leti Grenoble in the antennas and propagation laboratory (LAPCI). The main objectives of this work are: i) contribution to development of numerical tools for the design and optimization of superdirective compact arrays with beam-steering capabilities; ii) the study of new elementary sources for compact antenna arrays; iii) the realization and experimental characterization of a supergain compact array with circular polarization and beam-steering capabilities. This work will combine theoretical studies and model developments, antenna design using 3D electromagnetic software, prototyping and experimentations.
Microwave Near Field Sensing in Heterogeneous Media
This thesis focuses on the development of microwave near-field sensing techniques for applications in biomedicine, agronomy, and geophysics. The primary objective is to design low-complexity algorithms that effectively solve complex inverse problems related to the characterization and detection of dielectric properties with various geometric distributions in heterogeneous media.
The candidate will begin by conducting a comprehensive review of existing radar-based and advanced signal processing methods. A precise physical model of microwave propagation in near-field conditions will be developed, serving as the foundation for new detection methods based on the concept of physics-driven iterative tomography. The ultimate goal is to formulate efficient algorithms suitable for real-time applications and validate them through experimental implementation. To achieve this, an evolving prototype setup will be developed, progressing from 2D media to more complex 3D scenarios.
This interdisciplinary project combines physical modeling, algorithm development, and practical experimentation. It presents an opportunity to advance the field of microwave imaging, with significant implications for biomedical and environmental applications.
Multiphysical modeling of a dual-frequency induction-heated metallothermic reactor
The recycling of uranium extracted from spent fuel (reprocessed uranium or URT) is of major strategic interest as regards both closure and economics of the cycle as well as for national sovereignty. France has initiated the development of a reprocessing route for this URT, involving an entire production chain relying on SILVA laser enrichment technology.
In this context, the CEA is in charge of developing all the processes in this chain, in particular the steps involved in the conversion of uranium oxide into uranium metal required for laser enrichment. For this purpose, the “Laboratoire d'étude des technologies Numériques et des Procédés Avancés” (LNPA) is studying the transposition of the historical metallothermy process to a cold crucible type reactor. This dual-frequency inductive furnace is designed to melt a two-phase charge consisting of a fluorinated slag and a metal produced in situ by the metallothermic reaction.
Alongside a multi-year technology development program on reduced-scale inactive pilot plants, numerical modeling studies of the reactor are undertaken in order to consolidate the change in working scale and enable system parameters to be optimized before deployment of the technology in active operation on depleted uranium for validation tests. The aim of the proposed thesis work is to develop the magneto-thermo-hydraulic (MTH) multiphysical model of the cold crucible metallothermic furnace.
Design of electrically small antennas for connected object applications
This doctoral project focuses on the design of innovative antennas suited for Internet of Things (IoT) applications, addressing major challenges related to size, performance, and integration. The scientific context is based on the growing demand for electrically small and efficient antennas, capable of seamlessly integrating with IoT devices while maintaining high radiation efficiency. The proposed work involves the creation of electrically small antennas, optimized for performance, tunability, and compatibility with electronic and metallic environments. The designs will explore various types of antennas, such as loops, F-type antennas, top-loaded monopoles, and metallic cage structures, incorporating state-of-the-art tunable components.
The main objectives include benchmarking the performance of these antennas against theoretical physical limits (e.g., Chu/Gustafsson), analyzing dielectric and metallic losses, and achieving dual-band reconfigurability tailored to communication standards. The candidate will use electromagnetic simulation tools, develop behavioral models, and create prototypes, as well as conduct performance tests in anechoic chambers. The expected outcomes are highly efficient, frequency-agile miniature antennas that will advance the understanding of electromagnetic radiation phenomena for compact antennas and meet the requirements of tomorrow's connected objects.