Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

Miniature and directive antenna design with frequency agility over several octaves

Département Systèmes

Laboratoire Antennes, Propagation, Couplage Inductif

01-09-2019

SL-DRT-19-0423

serge.bories@cea.fr

The 'New Space' sector pushes for innovative solutions concerning on board micro-satellites antenna design. With smaller satellites, the miniaturization of directive and extremely wide band antenna represents a solution to fill the requirements of a lot of services. The double circular polarization needs to be ensure properly over more than 2 octaves. The CEA Leti antenna laboratory proposes to skirt the classical antenna physical limitation (bandwidth / miniaturization) by tuning the antenna on a smaller instant sub-band that can be shifted with reconfigurable RF components. This is the concept of antenna aperture tuning. The novelty of the PhD subject is to extend the tuning range over several octaves thanks to tunable capacitors developed at CEA Leti. The challenge consists to optimize the miniaturization of the antenna structure while limiting the impact of losses introduced by the tunable capacitors and get a performance stability over several octaves. Prototypes will be realized and measured in the CEA Leti or CNES anechoic chamber.

Study of new solutions for the security of embedded systems

Département Systèmes

Laboratoire Sécurité des Objets et des Systèmes Physiques

01-02-2019

SL-DRT-19-0426

pierre-henri.thevenon@cea.fr

In recent years, the number of connected systems has increased exponentially and is expected to reach several tens of billions by 2020. Most of these devices integrate seldom, if ever, security and can create massive attacks involving a large number of objects. In the embedded systems used in IOT and I-IOT, hardware and software solutions currently exist and provide cryptographic primitives to secure a communication interface or data storage. However, these solutions are not always correctly implemented and didn't deal with all the issues of security. Based on the study of existing attack scenarios, standards and regulatory documents, this thesis will define the needs in terms of security of an embedded system throughout its life cycle. Particular attention should be paid to threat detection, hardware and software integrity, system resilience, and the definition of a new commissioning interface. New solutions will be studied and developed in order to address issues not integrated in current embedded devices. The implementation of these new solutions will be the first step in the development of a new component called a security supervisor. One day, this component could be integrated in most of embedded systems in order to strengthen defence in depth.

Wireless Communication Relying on Artificial Intelligence

Département Systèmes

Laboratoire Sans fils Haut Débit

01-09-2019

SL-DRT-19-0430

jean-baptiste.dore@cea.fr

In wireless communications, we are used to design transmit signals that enable straightforward algorithms for symbol detection for a variety of statistical channel and system models. In practice, real systems have many impairments (non-linear power amplifiers, antennae coupling effects, finite resolution quantization) that cannot be fully captured by tractable models. Artificial Intelligence-based approaches could be a disruptive but yet promising alternative. More precisely one can expect benefits of IA based approach in case of complex communication scenarii and when mathematical models are intractable. The first challenge of this PhD project is to assess the potential of IA in the design of a signal processing algorithms. The second challenge is to develop tailored learning methods that exploit a dataset to enable future communication systems to be self-configurable regarding its environment.

Flexible nanosensors matrix for impact detection on sensitive surface

Département Systèmes

Laboratoire Autonomie et Intégration des Capteurs

01-09-2019

SL-DRT-19-0434

elise.saoutieff@cea.fr

The aim of the PhD thesis is to implement a matrix of flexible piezoelectric nanosensors, which enable the 3D reconstruction of a force or deformation field. The nanosensors based on GaN nanowires obtained by directed growth are fabricated and assembled at CEA. The candidate will tackle experimental aspects, which include the fabrication and the assembly of sensors and sensor networks (matrix) via controlled growth and deposition processes, first-level flexible electronic layers (interconnects), system integration on an object (mechatronics) and finally signal collection and processing through a dedicated reading electronics, to be designed based on the competences present in our laboratory. In parallel, the candidate will carry out studies at the fundamental level, such as investigating the mechanical transfer between the nanowire and its environment and its effect on the generated signal under deformation, or the study of the piezoelectric / pyroelectric coupling intrinsic to GaN nanowires. For this purpose, the candidate will have access to multi-physics simulation tools. Finally, investigations on the choice of materials and the characterisation thereof (structural, mechanical, thermal, optical, electrical) will be pertinent and may pursued. More generally, this PhD thesis will also provide the opportunity to develop applicable solutions in various fields such as deformation and impacts detectors for predictive maintenance, sensitive surfaces or electronic skin.

Adaptative frequency tuning electronic systems for broadband vibration energy harvesting

Département Systèmes

Laboratoire Autonomie et Intégration des Capteurs

01-10-2019

SL-DRT-19-0436

pierre.gasnier@cea.fr

Energy harvesting is a theme whose goal is to supply power to communicating Wireless Sensor Nodes (WSN) by replacing their electrical power source (battery, cables) or by increasing their energy autonomy. Vibration energy harvesting, in particular, makes it possible to exploit the mechanical energy of an environment and convert it into electricity in order to supply the WSN. The proposed PhD thesis will focus on the use of the piezoelectric transduction to convert vibration energy into electricity. One of the major drawbacks of these harvesters is their frequency selectivity: the use of mechanical resonators amplifies ambient vibrations, but the harvested power drastically drops when the harvester and the environment are no longer tuned in frequency, which degrades the operability of the system and therefore its reliability. For the adoption of this type of system by industry, one of the main major barriers is therefore this frequency selectivity. This can be solved by means of so-called "broadband" harvesters and/or with the ability to be dynamically tuned by an electronic system. Indeed, coupled to an intelligent electronics, a "strongly coupled" harvester can see its mechanical behaviour modified (change in its stiffness for example) which makes it possible to 1) follow the evolution of the input frequency (a motor whose rotation frequency slows down, ...) and/or 2) compensate for its own intrinsic properties (its resonance frequency that decreases with temperature, ageing...). The core of the proposed work therefore focuses on electronics and power management circuits that adapt the mechanical behaviour of such harvesters according to the input vibration. The CEA and the Savoie Mont-Blanc University (SYMME Laboratory) have already proposed high-performance techniques to carry out this frequency tuning. However, the automatic adjustment part of these circuits has not been investigated. The objective of the thesis is to propose, dimension, simulate, realize and test innovative electronic architectures allowing automatic tuning and maximum power point tracking of a piezoelectric harvester. After a state of the art study on frequency adjustment means and techniques, a system study and electromechanical simulations will have to be carried out, which will make it possible to select the relevant implementations (Full analog, or mixed digital-analog). Particular care will be taken to ensure that the proposed circuit is low power and takes up little space, since the ultimate goal is to build a circuit that is autonomous in terms of energy and consumes a negligible proportion of the harvested electrical energy. At the end of the Phd work, the selected architecture(s) will then be proposed to the integrated circuit design department for miniaturization. A complete demonstrator (harvester + tuning technique + adjustment circuit) is targeted at the end of this thesis.

Enhancements of Deterministic Ultra-Reliable Low Latency Communication (URLLC) Protocols by opportunism

Département Systèmes

Laboratoire Sans fils Haut Débit

01-09-2019

SL-DRT-19-0442

mickael.maman@cea.fr

The fifth-generation cellular mobile networks are expected to support ultra-reliable low latency communication (URLLC) services. The requirements of URLLC applications are: - End-to-end latency down to 1ms - Determinism (i.e. whether the latency is stable) down to 1µs - Reliability (i.e. success probability of transmitting a certain number of bytes within a certain delay) between 99.999% and 1-10^-9 - Availability (i.e. percentage of time end-to-end communication service are delivered according to an agreed QoS) up to 99.99% - Connection density (i.e. the number of devices fulfilling a target QoS per area) of 10^6/km² for massive deployment or 100/m² in certain area - Lifetime up to 15 years All requirements can hardly be reached together. During the PhD, we will focus on a flexible tradeoff between reliability and latency. Some proposals propose to exploit diversity in terms of time, frequency, space, antenna, interface to improve the latency/reliability limits. Moreover, in the case of URLLC applications, the strict latency requirements could exclude protocols that rely on retransmission. In this PhD, we propose to study a novel transmission and allocation (PHY/MAC) method providing a flexible tradeoff between reliability and latency. For that purpose, we propose to enhance URLLC deterministic protocols (providing the minimal QoS) by opportunism. Taking into account that URLLC applications have a range of requirements (in terms of reliability and latency), our approach will mix resource reservation and opportunistic use of the spectrum. On the one hand, we will exploit existing or propose deterministic protocols to provide the minimal QoS requirements (e.g., minimal reliability, minimal availability, maximal latency without jitter) in order to ensure low latency and reliable communications. This approach will bound the performance. On the other hand, we will enhance the QoS (ultra-reliable or ultra-low latency) thanks to an opportunistic approach. This complementary protocol will share limited resources (shared/unused) for heterogeneous URLLC services and will improve the reliability by exploiting spatial and frequency diversity and propose a better latency (but with jitter). Thanks to this approach, we are allowed to overbook the shared resource and we can naturally provide heterogeneity management.

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