Jerome Rossignol

An experimental study on magnetic near-field (NF) scanning of printed circuit board (PCB) emission radiation is developed in this paper. The design and installation of the electromagnetic (EM) NF scanner is introduced. The test bed of magnetic NF emission in the microwave frequency range is described. The methodology of the microstrip magnetic NF probe is discussed. The probe calibration process was performed following the IEC 61967-1 NF scanning standard. The NF scanner functioning is tested with passive microstrip circuit square loop probe and device under test (DUT) PCB radiation in the test plan positioned at 1-mm above the ground plane. Based on the standard test with I-shape 50-$Ω$ transmission line (TL), the calibration process of radiated magnetic field was validated by comparison between HFSS__ simulation and experimentation in very wideband frequency from 0.1-GHz to 3-GHz. Then, a nonstandard TL based DUT was experimented. Accordingly, the cartographies of scanned magnetic NF at two different test frequencies, 2 GHz and 3 GHz, are discussed. The NF scanner is under development for targeting the EMC radiated emission of PCB dedicated to operate in 6G wireless communication.

Previous studies have shown that the incorporation of sulfonated metallophthalocyanines into sensitive sensor materials can improve electron transfer and thus species detection. Herein, we propose a simple and easy alternative to the use of generally expensive sulfonated phthalocyanines by electropolymerizing polypyrrole together with nickel phthalocyanine in the presence of an anionic surfactant. The addition of the surfactant not only helps the incorporation of the water-insoluble pigment into the polypyrrole film, but the obtained structure has increased hydrophobicity, which is a key property for developing efficient gas sensors with low sensitivity to water. The obtained results show the effectiveness of the materials tested for the detection of ammonia in the range of 100 to 400 ppm. It is shown by comparing the microwave sensor responses that the film without nickel phthalocyanine (hydrophilic) produces greater variations than the film with nickel phthalocyanine (hydrophobic). These results are consistent with the expected results since the hydrophobic film is not very sensitive to residual ambient water and therefore does not interfere with the microwave response. However, although this excess response is usually a handicap, as it is a source of drift, in these experiments the microwave response shows great stability in both cases.

This paper proposes an innovative approach for the real-time detection and quantification of ammonia using machine learning models and a microwave gas sensor. The objective is to predict in real time the ammonia concentration over a range of 0 to 400 ppm. The used sensor is a microwave multi-resonator recovered by a sensitive material (TiO2) put in the presence of ammonia in the air at room temperature. The sensor response is the reflected coefficient (magnitude and phase for each used frequency). The experiments are monitored by a mass spectrometer which defines the ground truth used to train machine learning models. Several regressors are tested and compared using time samples of the sensor response and Pearson’s correlation is applied on the data to extract the relevant features. The influence of the type of sensor response on the machine learning performances is studied as well as the ability of the models to adapt to a given data set of random concentrations never seen during training. The best models are Random Forest (MAE: 34 ppm, R²: 0.87) and Multi Layer Perceptron (MAE: 31 ppm, R²: 0.88) obtained with the magnitude and phase response of the sensor. The last one gives the best prediction time (3.44 ms) and can be used for real time embedded ammonia concentration measurements.

Molecularly imprinted sol–gel silica (MIS) coupled to a microwave sensor was designed and used to detect phenylacetaldehyde (PAA), a chemical tracer of wine oxidation. The developed method is fast, cheap and could replace the classical chromatographic methods, which require a tedious sample preparation and are expensive. To reach our objective, five MIS and their control non-imprinted silica (NIS) were synthesized and their extraction capacity toward PAA was studied in hydro alcoholic medium. The selected polymers, based on this first step, were subjected to a selectivity study in the presence of PAA and three other competing molecules. The best polymer was integrated in a microwave sensor and was used to assess PAA in red wine. The developed sensor was able to detect PAA at the µg·L⁻¹ level, which is below the off-flavour threshold.

Sensors based on "resonance phenomenon" span a broad spectrum of important current applications including detection of biological and chemical agents, and measurements of physical quantities. Resonance phenomena occur with all types of waves: electromagnetic, optic, and acoustic. This review reports about the most recent advances in the design and applications of resonant "passive" sensors, i.e. resonant sensors able to operate with a distant power source and/or able to communicate with a distant transceiver. The sensors considered in this review include acoustic, magnetoelastic, and electromagnetic transducers. They are presented through their relevant technological aspects and through they major advantages which include their integrability within embedded systems and/or systems requiring energy autonomy. Furthermore, the use of these resonant sensors is illustrated in a large variety of applications, ranging from environmental monitoring, structural health monitoring, food packaging monitoring, wearable or implanted sensors for the monitoring of physiological parameters in healthcare related applications, to IoT and future industry monitoring applications.

A molecularly imprinted silica (MIS) coupled to a microwave sensor was used to detect three fungicides (iprodione, procymidone and pyrimethanil) present in most French wines. Chemometric methods were applied to interpret the microwave spectra and to correlate microwave signals and fungicide concentrations in a model wine medium, and in white and red Burgundy wines. The developed microwave sensor coupled to an MIS and to its control, a nonimprinted silica (NIS), was successfully applied to detect the three fungicides present in trace levels (ng L⁻¹) in a model wine. The MIS sensor discriminated the fungicide concentrations better than the NIS sensor. Partial Least Squares models were suitable for determining iprodione in white and red wines. A preliminary method validation was applied to iprodione in the white and red wines. It showed a limit of detection (LOD) lower than 30 ng L⁻¹ and a recovery percentage between 90 and 110% when the iprodione concentration was higher than the LOD. The determined concentrations were below the authorized level by far.

In this paper, authors propose a study on microwave gas sensors and the influence of critical key parameters such as the sensitive material and the circuit conception process. This work aims to determine the influence of these parameters on the quality of the final response of the microwave gas sensor. The fixed geometry of the sensor is a microstrip interdigital capacitor coated with a sensitive layer excited with two 50 Ω SMA ports. The sensitive material has been chosen in order to interact with the target gas: ammonia. Indeed, this gas interacts with phthalocyanine and metal oxides like hematite, TiO₂. To explore the effect of the circuit manufacturing process, three series of samples are prepared. The first series of sensors is produced by classical UV photolithography (process) in the laboratory. The second series of sensors is produced by a subcontractor specialized in rf circuits. The third series is obtained by the experimental platform of the FEMTO-ST laboratory with EVG620 Automated Mask Alignment System Nanoimprint lithography in a clean room. To examine the reliability of this gas sensor at room temperature, it was exposed to different ammonia gas concentrations from 100 to 500 ppm in an argon flow to eliminate coadsorption phenomena. According to the recorded frequency responses, the reflection and transmission coefficients show a change of resonance amplitude due to electrical characteristic modification. This can be correlated to the presence of gaseous ammonia. The chemical nature of the sensitive material layer has a major influence at the excited frequency range. The process of conception influences the sensor sensitivity. The analysis of the results shows a strong correlation between the injected ammonia concentration and its frequency response. The influence of the critical key parameters cited is discussed here.

This work presents new elements of understanding for the microwave-based gas sensors behavior at room temperature. A TiO₂-covered microstrip interdigital capacitor was submitted to various ethanol concentrations and showed a proportional response in the 1–10 GHz microwave range. For each concentration and right after ethanol injection, the sensor response presented a slight overshoot which is often found in gas sensors studies. Near ambient pressure photoemission experiments (NAP-XPS) were conducted to explore the physicochemical causes of this overshoot, and demonstrated the formation of an ethoxide during ethanol adsorption.

This proposal is devoted to a collaborative approach dealing with microwave microscopy experiments. The application is dedicated to an electromagnetic field cartography above circuits and the influence of nanometric material layer deposition on the circuits. The first application is associated to a microstrip ring resonator. The results match with the simulated fields. The second application is focused on the effects of a dielectric layer deposited on the circuit and its impact in terms of electromagnetic propagation.