FERRAH Lisa

Abstract: Analog circuits are essential to the development of information and wireless communication technologies. They operate over a wide frequency range (100 MHz to 300 GHz) and play a key role in mobile communications, filtering, modulation/demodulation, and power management to ensure transmission quality. They also support high-capacity telecommunications infrastructures without major constraints on physical space. However, the rise of the Internet of Things and embedded electronics requires circuits that are increasingly miniaturized and energy-efficient. The miniaturization of radio-frequency components is therefore indispensable to meet the growing demands of embedded systems, combining compactness, performance, and reliability under strict constraints of size, weight, and power consumption. It enables space optimization and the integration of additional functionalities. Nevertheless, this miniaturization faces a fundamental limitation linked to the size of the electromagnetic wave: key elements such as filters, waveguides, and antennas have dimensions that scale with frequency and material properties, which restricts the extent of achievable physical reduction.
This research aims to overcome the fundamental limitation imposed by the electromagnetic wavelength in order to further miniaturize RF components. It focuses on the use of materials with engineered electromagnetic properties, capable of reducing the propagation velocity and guided wavelength while preserving signal quality and minimizing losses.
Conventional dielectric materials, with limited permittivity values (ε between 1.5 and 30) and permeability close to 1, currently restrict the optimization potential of electromagnetic performance. The main objective of this thesis is therefore to design a technological building block in the form of a “slow-wave waveguide,” together with its EM model compatible with RF design tools and adaptable to technological constraints or target frequency bands. This building block will then be demonstrated through the redesign of an RF function (such as a filter, phase shifter, or coupler) with significantly reduced size.
To achieve this goal, three main tasks will be addressed throughout the PhD work:
Design and simulation of slow-wave waveguides
Fabrication of slow-wave waveguides
Advanced electrical and structural characterization