Author: Davide Galetti.
Title: Non-ferromagnetic metal detecting system for agricultural applications.
Tutor: Luca Vincetti
Co-tutor: Stefano Lenzini, Riccardo Ferretti Corradi.
Abstract: The purpose of this thesis is to design a detection system for non-ferromagnetic metals for agricultural applications.
After a literature study on the existing industrial detection techniques the balanced coil principle has been selected. The design of the proposed system has been performed through simulations in which the effects of the environment were also considered.
A prototype has been realized and measurements in different environmental conditions have been conducted. The collected data are exposed in comparison with simulations. Experimental measurements show that the proposed system is suitable for agricultural applications. Non-magnetic metal pieces are detected with an acceptable accuracy even in the most difficult environmental conditions. Finally, possible improvement and future works are illustrated.
Author: Natale Cardile.
Title: Design and prototyping of a sensor for monitoring grain level in agricultural machinery.
Tutor: Luca Vincetti
Co-tutor: Stefano Lenzini, Federico Melli.
Abstract: During the last years, electromagnetic sensors, due to their high precision and low cost, have been increasingly used in many fields. In this thesis work, the attention has been focused on the development of a capacitive sensor for level detection and monitoring of the filling status of crop materials within agricultural machines. After an in-depth analysis of the state of the art of level sensors and the possible solution to be employed, the interdigital co-planar capacitive sensor has been chosen. In literature, this sensing topology has been used for dielectric permittivity characterization of liquids, moistures, and gasses. Nevertheless, its working principle can be exploited for the purpose of this thesis. In fact, this type of sensors can be shaped to fulfil the sensitivity requirements of the sample under test. Furthermore, this is a planar solution that can be realized on a low-cost PCB while maintaining a low encumbrance. First, a theoretical and numerical study on the electrical properties of the sample materials has been conducted. Then, through numerical simulations, the sensor has been designed by taking into account the sample characteristics and the front-end electronics sensitivity. Finally, a prototype has been realized and experimental measurements have been carried out in a realistic environment. The measurements show satisfactory results in term of height level sensitivity of the crop sample.
Author: Riccardo Ferretti Corradi.
Title: Design and Prototyping of Microstrip Resonators for electromagnetic characterization of dietectric materials.
Tutor: Luca Vincetti
Co-tutor: Stefano Lenzini, Luca Ferrari.
Abstract: The exact characterization of the electromagnetic properties of dielectric material is increasingly required in different industrial fields.
The purpose of this thesis is to design and prototype a sensor able to measure these properties that has to be included in agricultural machinery. The samples to analyze are, then, different agricultural products that have a non-uniform density.
The chosen technology is based on a resonant measurement technique that relies on microstrip resonators. In fact, due to its working principles, this technology could be used without the need to make a resonant cavity at low frequency that would be a major issue in terms of size.
After a literature study on the existing permittivity measurements techniques the design of the chosen method has been performed through simulations. Then, different prototypes have been realized and measurements on different samples have been conducted.
Finally, the collected data are exposed jointly with some possible future improvements.
Author: Anna Maria Ricotta.
Title: Design and prototyping of beam steerable antennas array for V2X applications.
Tutor: Luca Vincetti
Co-tutor: Stefano Lenzini, Moreno Maini
Abstract: In the last years, patch antennas gained popularity in wireless applications thanks to its low size, low weight and low cost, characteristics which makes them very attractive also for automotive applications.Vehicular networks, nowadays, receive great attention and different technologies have been studied to allow V2X communications, i.e., Vehicle-to-Vehicle, Vehicle-to-Infrastructure and Vehicle-to-Pedestrian. The main goals of these communications are road safety and traffic efficiency. In particular, for direct vehicular transmissions, a 75 MHz of band has been allocated in the vicinity of 5.9 GHz.The purpose of this thesis is to provide a possible solution for the design of an array of patch antennas suitable for vehicular applications. The proposed antenna array consists of a 4×4 configuration composed by a 4-element corporate-fed array in which each radiating element is made up of a 4-element series-fed array. Furthermore, the switched line approach is used to tilt the radiation pattern of 10°, 20° and 30°. In this way, by reaching the desired beam direction, it is demonstrated that this structure can be used for real time beam steering applications. The design and simulations are accomplished using CST Microwave Studio, moreover, physical prototypes are made to verify the feasibility of the antenna. The proposed solution shows satisfactory performances and good agreement between simulated and measured results can be observed.
Author: Federico Melli.
Title: Design and prototyping of low profile 3D antennas for roof-top LTE vehicular applications.
Tutor: Luca Vincetti
Co-tutor: Enrico Coscelli, Stefano Lenzini
Abstract: Cellular communication is becoming more and more important for the connected vehicles applications. In particular LTE is the last implemented cellular standard for automotive communication. These thesis has been developed in collaboration with Ask Industries and its aim is to provide the project of new types of radiating elements which works at LTE frequency bands. The material used, which is metallic sheets, and the 3D shape are the peculiarity of these antennas. The 3D shape allows to have a low profile and to efficiently occupy the small available volume. The trend is to put two LTE antennas under the shark-fin case in order to exploit the MIMO functionalities. In the former part of the work, the design criteria and the simulations results are presented. In the latter part the prototyping process is described and a comparison between experimental measurements and simulations is shown. To evaluate the performances of these antennas, a PCB antenna model of the company’s portfolio is used as benchmark. The 3D prototypes reached the performances of a standard PCB antenna, but the use of metal sheets ,instead of PCB, can dramatically decrease production costs.Eventually some possible improvements are suggested.
Author: Giacomo Mellone.
Title: Novel laser source for flow cytometry applications.
Tutor: Luca Vincetti
Co-tutor: Matthieu Chafer, Fetah Benabid
Abstract: Flow cytometry is a technology for cell counting and cell sorting. It presently is an essential tool in biomedical applications such as DNA sequencing or diagnosis of health disorders. The current cytometers rely on exciting a stream of suspended cells by up to three lasers, each emitting at different wavelengths, and recording the light from scattering and fluorescence of the cells, which are tagged with specific fluorescent bio-markers. The recorded light is then processed to extract information related to cell counting, sorting and structure.
A key performance parameter in a cytometer is the laser power and its spectral coverage. Having a large set of visible and UV lasers available allows increasing the instrument flexibility, inspecting more physical and chemical properties of the particles at a time. So far, the common laser technology is limited in providing both sufficient power density and spectral coverage. Furthermore, having more than three different lasers implies an increase in costs and complexity.
The intent of the present work is to explore a new laser source developed by the company GLOphotonics and coined CombLas. This radiation source emits a comb of laser lines in the UV-VIS and NIR. It is based on Stimulated Raman Scattering (SRS) in a hydrogen-filled Hollow-Core Photonic Crystal Fibre (HC-PCF). This work reports on the properties and the generation of the rotational and vibrational Stokes and anti-Stokes lines. Such a Raman comb is generated and analyzed using two types of HC-PCFs: a Kagome lattice HC-PCF and a Tubular lattice HC-PCF, which are pumped with a compact 532nm DPSS laser.
The conversion efficiency to the higher order Raman lines is proportional to the pump laser pulse energy, which in the case of our laser decreases of repetition rate. On the other hand, the cytometer signal strongly depends on the laser average power, and hence on the repetition rate. Hence, this requires a trade-off in operating in sufficiently high energy to generate a strong Raman comb, and sufficiently low so to have the required high repetition rate. In the case of our system, when the DPSS laser is emitting its maximum energy of 115 μJ at 50kHz, the Raman comb is well populated by a total number of 31 rotational and vibrational Stokes and anti-Stokes lines, and spanning from 368 nm to 1075 nm. However, at a repetition rate of 210kHz, the maximum pulse energy is reduced to 22 μJ, and 2 only vibrational lines survive.
Two higher order Raman lines have been studied and sent in the cytometer: the first consists of the first order rotational Stokes @549nm and the second consists of first order vibrational anti-Stokes @435nm. Those have been extracted both using a grating and bandpass filters. In the second case, the quality and power of laser beam proved to be better for our intents. The measurements were conducted on running Rainbow Fluorescent particles in the Flow Cytometer and the relation between power, repetition rate and correct beads illumination has been investigated. Fluorescence histograms show that a comb generated with a pump operating at a repetition rate as low as 180kHz and average power as low as 4 mW provided good results.
In comparison with state-of-the-art and cytometry requirements, the current results from this novel source are promising and demonstrate the viability of such Raman comb Raman for Flow Cytometry applications. However, improvements must be done to further increase the repetition rates whilst still generating a strong comb, allowing to illuminate the greater number of cells possible.
Author: Stefano Lenzini.
Title: Complex permittivity measurement techniques of solid and liquid materials at microwave frequencies.
Tutor: Luca Vincetti
Abstract: The measurement of the materials dielectric permittivity is nowadays required in the industrial eld and is very useful in what is concerning the microwave sector.
In this thesis different existing measurement techniques are analyzed and compared.Some of them are exploited for the characterization of two materials: an hydraulic oil, new and used, and a speci c crop sample. In particular the performed techniques are: the coaxial probe and the resonant cavity one. For the rst the commercial sensor HP85070B is used. For the second technique two different types of cavities are considered: a cylindrical resonant cavity and a coaxial resonant cavity.
The cylindrical cavity is initially studied through simulation for discover the best ways of using it, then the measurements are performed.The coaxial resonant cavity is designed for satis es different parameters such as the frequency range.
Finally, an analysis of the obtained data and possible future improvements are given.