Miniaturization and miniature antenna electronic reconfiguration for the IOT.

Keywords  : 
Electromagnetism, Radiofrequency, Miniaturization, Compact Antenna, Microtechnology,

Abstract :
The miniaturization of antennas for the Internet of Things (IoT) represents a significant technological challenge, as it requires reducing antenna dimensions while preserving reliable communication performance. This progress is key to enabling more compact and efficient IoT devices, which are crucial for seamless and ubiquitous wireless connectivity across diverse environments. Nevertheless, miniature antennas are inherently constrained by fundamental physical limits in bandwidth, gain, and efficiency. These parameters are closely related to the antenna’s electrical size, establishing unavoidable performance bounds for electrically small antennas.
The central objective of this thesis is to investigate the design of a miniature antenna that can be integrated into an RF chip package, while ensuring sufficient bandwidth and efficiency for IoT applications. Since achieving a wide bandwidth is unfeasible within these constraints, the antenna must rely on a frequency-agile system. While fundamental boundaries on the bandwidth and directivity of small antennas have driven a significant body of work, it is only recently that authors have proposed radiation efficiency bounds, owing to the greater physical complexity of dispersion phenomena. In relation to the analysis of these boundaries, a survey of antennas reported in the literature with small electrical sizes is presented and discussed in light of these new limits.
A dedicated theory chapter examines the quality factor limits of resonant antenna structures. Equivalent circuit models, based on Chu’s equivalent spherical mode circuits, are proposed for both a canonical dipole and a planar loop on a substrate. The developed models were shown to yield accurate results over a defined bandwidth and demonstrated strong potential for advancing the understanding of the limitations of such structures, as well as the influence of surrounding lossy media.
Investigations on antenna structures suitable for cubic antenna designs were also conducted. After evaluating different candidate architectures, an optimized design was proposed for RF chip package integration. Two prototypes were fabricated and measured during the course of this work. The first served as a proof of concept, while the second incorporated a novel multiple-feed system to enhance the antenna’s frequency agility. Both prototypes were thoroughly analyzed, demonstrating the practical feasibility of the proposed approach.

Jury members :

• Tan Phu VUONG, UNIVERSITY PROFESSOR - Grenoble INP - UGA : Supervisor
• Robert STARAJ, UNIVERSITY PROFESSOR - Côte d’Azur University : Examiner
• Ala SHARAIHA, UNIVERSITY PROFESSOR - Rennes University : Reviewer
• Anja SKRIVERVIK, PROFESSOR -Federal Institute of Technology Lausanne : Reviewer
• Pascal XAVIER, UNIVERSITY PROFESSOR - Grenoble INP - UGA : Examiner
• Christophe DELAVEAUD, RESEARCH DIRECTOR - CEA Grenoble Center : CoSupervisor
• Laure HUITEMA, ASSISTANT PROFESSOR HDR - Limoges University : Examinerr
• Erika VANDELLE, DOCTOR OF SCIENCE - CSEM : Examiner