Thesis defence of Aïcha Saïd (RMS team): Biosensor using near field millimeter wave propagation

Aïcha SAÏD - RMS team

Thesis of Université Grenoble Alpes prepared at DSYS/STSF/LAIR laboratory (CEA-Leti), under the direction of Sylvain Bourdel, co-supervised by Frédéric Hameau, Rémy Vauché and Alexandre Siligaris.

Composition of the jury
Sylvain BOURDEL - Thesis director - Full professor - Grenoble INP / TIMA
Éric KERHERVÉ - Rapporteur - Full professor - Université de Bordeaux
David DUBUC - Rapporteur - Full professor - Université de Toulouse LAAS
Florence PODEVIN - Examinator - Full professor - Grenoble INP / TIMA
Serge VERDEYME - Examinator - Full professor - Université de Limoges, XLIM
Pierre SABOUROUX - Examinator - Associate professor - Université Aix-Marseille, Institut Fresnel
Frédéric HAMEAU - Thesis supervisor - CEA-Leti
Rémy VAUCHÉ - Co-thesis supervisor - Université d'Aix-Marseille, IM2NP
Alexandre TSILIGARIS - Co-thesis supervisor - CEA-Leti

Title: Biosensor using near field millimeter wave propagation
Keywords: bio-sensor, impedance detector, CMOS, reflection, coefficient phase variation
Abstract:  Traditionally, the diagnosis of melanoma and skin cancer requires, initially, a biopsy prescribed by a doctor. This invasive procedure involves taking a sample for examination under a microscope. Subsequently, a scanner can be used to assess the spread of cancer to other organs. While these solutions reliably and accurately detect various types of melanomas, they remain invasive, such as in the case of a biopsy, or cumbersome and energy-consuming when it comes to a scanner. However, the progress in integrated technologies now allows for the development of systems that can perform initial patient diagnostics and ensure their monitoring without necessarily resorting to invasive, time-consuming and expensive procedures.

Indeed, biological tissues exhibit dielectric behavior. They are characterized by their conductivity and permittivity properties. Consequently, any change in the biological properties of the tissue can be observed through its dielectric properties. This analysis can be carried out by evaluating the interaction of electromagnetic waves with the environment. Therefore, this observation leads to potential advancements in near-field radiofrequency sensor solutions for biomedical analysis.

For novel biomedical applications, such as sweat detection or melanoma identification, solutions from the radiofrequency domain, especially at millimeter-wave (mmW) frequencies, are proposed. Radiofrequency solutions take advantage of non-invasive, integrated, and low-cost systems. Moreover, working in this frequency range takes advantage of shallow penetration into the skin, ensuring a minimal signal interference with tissues beyond the dermis. The objective of this thesis is to develop an integrated system to analyze the variation of the impedance presented by the sensor to detect changes in the dielectric parameters of a given sample.

Throughout this thesis, a study led to the design and validation of an integrated circuit in CMOS 45 nm PD SOI technology, enabling measurement of the phase of the reflected signal from the sensing element in the millimeter-wave band, around 60 GHz. The proposed circuit, based on a reflectometry system, is composed of a directional coupler for transmitting and receiving an RF signal from the sensor, along with an IQ demodulator to provide an output baseband signal and to measure the phase. A second circuit was designed and measured around 60 GHz to enhance detection sensitivity through feedback on the coupler. The designed circuit consists of a leakage-cancelling system, composed of a variable phase shifter and a variable attenuator, fed by the coupler to improve its isolation and thus the system accuracy. Both circuits have been measured to validate their functionality and performance.