Noncontact sensing technologies have become increasingly central in a variety of fields, ranging from industrial monitoring to healthcare applications. In this context, the thesis focuses on the development and implementation of innovative techniques, electronic circuits, and devices for contactless sensing via wireless coupling, responding to the growing interest in noncontact measurement methods. The themes treated in this thesis regard both the scenario of distant noncontact sensing in the electromagnetic far field, and proximate wireless sensing, leveraging on near-field electromagnetic interactions. Each domain is distinctly characterized by its specific technologies, applications, and methodologies, reflecting their operational ranges and fundamental principles. In the domain of distant wireless sensing, the thesis investigates the use of electromagnetic waves for unobtrusive level monitoring of granular solids in silos. This system, developed employing a commercial frequency-modulated continuous-wave radar sensor, demonstrates the potential of this technology in unobtrusive monitoring in agricultural and industrial environments. Considering the proximate wireless sensing domain, the thesis provides an analysis of noncontact interrogation of passive sensors and it presents different approaches and applications. It addresses the challenges and offers solutions for enhancing the reliability and accuracy of contactless measurements, which can be advantageously independent of the interrogation distance. This can path the way to the development of low-cost, disposable and sustainable devices for healthcare and industrial applications. In particular, the thesis presents a system for the noncontact measurement of the resonant frequency of piezoelectric MEMS resonators. The technique exploits magnetic coupling between interrogation and sensor units, and it is innovatively applied for temperature sensing exploiting a thin-film piezoelectric on silicon (TPoS) aluminium nitride (AlN) disk resonators and a contactless interrogation time-gated technique. Furthermore, the thesis presents a flexible patch for body temperature measurement, combining contact sensing with contactless readout, and exploiting magnetic coupling between interrogation and sensor units. The flexible patch, forming the sensor unit, is composed of an inductive coil for magnetic coupling, a ceramic capacitor used as the temperature sensing element exploiting its temperature coefficient of capacitance and an additional inductor to make the resonant frequency of the resulting resonant RLC circuit independent from the bending of the patch. Similarly, interrogation techniques have been applied to a novel method for contactless interrogation of an inductive sensor used for detecting conductive targets. The system features a solenoidal coil connected with a capacitor to form a resonating LC circuit, whose resonant frequency changes when a conductive target is introduced in the generated magnetic field. An external interrogation coil electromagnetically coupled to the inductive sensor enables the wireless measurement for conductive target detection. Lastly, the study introduces an advanced technique for the contactless interrogation of passive resistive sensors. The novel approach exploits the resonant frequency stability and the high quality factor of a quartz crystal resonator, used as a resonant element, with a series-connected resistor acting as the sensing element. This method overcomes the limitations of amplitude measurements techniques typically affected by the interrogation distance.
Le tecnologie per la misurazione di grandezze fisiche senza contatto sono diventate sempre più centrali in vari settori, che vanno dal monitoraggio industriale alle applicazioni sanitarie. In questo contesto, la tesi si concentra sullo sviluppo e l'implementazione di tecniche innovative, circuiti elettronici e dispositivi per la rilevazione senza contatto. L’analisi presentata all'interno di questa tesi considera lo scenario del rilevamento senza contatto a distanza nel campo elettromagnetico lontano (far-field) e al rilevamento senza contatto di prossimità, sfruttando le interazioni elettromagnetiche in campo vicino (near field). Nell’ambito del rilevamento senza contatto a distanza, la tesi indaga l'uso delle onde elettromagnetiche per il monitoraggio non invasivo del livello di solidi granulari all’interno di silos. Questo sistema, sviluppato impiegando un sensore radar commerciale a onda continua modulata in frequenza, dimostra il potenziale di questa tecnologia nel monitoraggio non invasivo e senza contatto in contesti agricoli e industriali. Considerando invece lo scenario del rilevamento senza contatto di prossimità, la tesi fornisce un'analisi dell'interrogazione senza contatto di sensori passivi e ne presenta diversi approcci e applicazioni. Vengono affrontate le problematiche delle misurazioni senza contatto, proponendo alcune soluzioni per migliorarne l'affidabilità e l'accuratezza, permettendo in particolare di renderle indipendenti dalla distanza di interrogazione. In particolare, la tesi presenta un sistema per la misurazione senza contatto della frequenza di risonanza di risonatori MEMS piezoelettrici. La tecnica proposta sfrutta l'accoppiamento magnetico tra un’unità di interrogazione ed un’unità sensore ed è applicata in modo innovativo per la rilevazione della temperatura, sfruttando le proprietà dei risonatori a disco in nitruro di alluminio (AlN) su silicio sottile piezoelettrico (TPoS) ed una tecnica di interrogazione senza contatto a tempo commutato. Inoltre, la tesi presenta un’etichetta flessibile per la misurazione della temperatura corporea, che combina il rilevamento a contatto della temperatura con una lettura senza contatto dell’unità sensore sfruttandone l'accoppiamento magnetico con un unità di interrogazione. L’etichetta flessibile, che costituisce l'unità sensore, è composta da una bobina induttiva che consente l'accoppiamento magnetico, un condensatore ceramico utilizzato come elemento sensibile alla temperatura, sfruttandone il coefficiente di temperatura della capacità, ed un induttore aggiuntivo utilizzato per rendere la frequenza di risonanza del circuito risonante RLC indipendente dalla flessione dell’etichetta. In modo analogo, le tecniche di interrogazione proposte sono state applicate ad un nuovo metodo per l'interrogazione senza contatto di un sensore induttivo, utilizzato per rilevare target conduttivi. Il sistema proposto presenta una bobina avvolta collegata con un condensatore per formare un circuito LC risonante, la cui frequenza di risonanza cambia quando un target conduttivo viene introdotto nel campo magnetico generato dalla bobina stessa. Attraverso una bobina di interrogazione esterna, accoppiata elettromagneticamente al sensore induttivo, è possibile interrogare senza contatto il sensore induttivo, permettendo quindi la rilevazione a distanza di target conduttivi. Infine, lo studio esposto in questa tesi introduce una tecnica avanzata per l'interrogazione senza contatto di sensori resistivi passivi, sfruttando risonatori a cristallo di quarzo come dispositivo risonante e basandosi sulla stima del fattore di qualità del circuito che costituisce l’unità sensore. Il metodo proposto supera i limiti delle tecniche basate su misure di ampiezza, legati in particolare all'influenza della distanza di interrogazione
Techniques, Circuits and Devices for Noncontact Sensing through Wireless Coupling / Zini, Marco. - (2024 Jun 20).
Techniques, Circuits and Devices for Noncontact Sensing through Wireless Coupling
ZINI, Marco
2024-06-20
Abstract
Noncontact sensing technologies have become increasingly central in a variety of fields, ranging from industrial monitoring to healthcare applications. In this context, the thesis focuses on the development and implementation of innovative techniques, electronic circuits, and devices for contactless sensing via wireless coupling, responding to the growing interest in noncontact measurement methods. The themes treated in this thesis regard both the scenario of distant noncontact sensing in the electromagnetic far field, and proximate wireless sensing, leveraging on near-field electromagnetic interactions. Each domain is distinctly characterized by its specific technologies, applications, and methodologies, reflecting their operational ranges and fundamental principles. In the domain of distant wireless sensing, the thesis investigates the use of electromagnetic waves for unobtrusive level monitoring of granular solids in silos. This system, developed employing a commercial frequency-modulated continuous-wave radar sensor, demonstrates the potential of this technology in unobtrusive monitoring in agricultural and industrial environments. Considering the proximate wireless sensing domain, the thesis provides an analysis of noncontact interrogation of passive sensors and it presents different approaches and applications. It addresses the challenges and offers solutions for enhancing the reliability and accuracy of contactless measurements, which can be advantageously independent of the interrogation distance. This can path the way to the development of low-cost, disposable and sustainable devices for healthcare and industrial applications. In particular, the thesis presents a system for the noncontact measurement of the resonant frequency of piezoelectric MEMS resonators. The technique exploits magnetic coupling between interrogation and sensor units, and it is innovatively applied for temperature sensing exploiting a thin-film piezoelectric on silicon (TPoS) aluminium nitride (AlN) disk resonators and a contactless interrogation time-gated technique. Furthermore, the thesis presents a flexible patch for body temperature measurement, combining contact sensing with contactless readout, and exploiting magnetic coupling between interrogation and sensor units. The flexible patch, forming the sensor unit, is composed of an inductive coil for magnetic coupling, a ceramic capacitor used as the temperature sensing element exploiting its temperature coefficient of capacitance and an additional inductor to make the resonant frequency of the resulting resonant RLC circuit independent from the bending of the patch. Similarly, interrogation techniques have been applied to a novel method for contactless interrogation of an inductive sensor used for detecting conductive targets. The system features a solenoidal coil connected with a capacitor to form a resonating LC circuit, whose resonant frequency changes when a conductive target is introduced in the generated magnetic field. An external interrogation coil electromagnetically coupled to the inductive sensor enables the wireless measurement for conductive target detection. Lastly, the study introduces an advanced technique for the contactless interrogation of passive resistive sensors. The novel approach exploits the resonant frequency stability and the high quality factor of a quartz crystal resonator, used as a resonant element, with a series-connected resistor acting as the sensing element. This method overcomes the limitations of amplitude measurements techniques typically affected by the interrogation distance.File | Dimensione | Formato | |
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