Radiowave propagation and antennas for high data rate mobile communications in the 60 GHz band

The 60 GHz MIMO systems are seen as some of the best candidates for the implementation of future high data-rate short range communications systems such as wireless personal area networks (WPAN). Although the performance of MIMO systems has been studied thoroughly theoretically and experimentally at lower frequencies like at 2 and 5 GHz, there is a clear lack of measurement data and experimental performance evaluations of MIMO techniques at 60 GHz. Furthermore, more effort is still needed in the design and evaluation of compact low cost 60 GHz antennas for communication applications. In the first part of the thesis, the first 60 GHz MIMO channel measurement system is presented. It is based on a previously developed 2 and 5 GHz sounder and frequency converters. This system uses virtual antenna arrays to create the channel matrix. A measurement campaign is reported. In order to improve the delay resolution, two other MIMO measurement systems are presented, based on an ultra wide band (UWB) sounder and a vector network analyzer (VNA). Those systems allow full characterization of the MIMO channel in the delay and angular domains. In the second part of this work, the performance of multi-antenna techniques is evaluated based on the measurement data obtained in the first part of the thesis. Three of the most promising multi-antenna techniques, namely MIMO, antenna selection MIMO, and beam steering, are analyzed and compared. The presented results indicate that the mutual information of the measured MIMO channel is quite close to that of the independent and identically distributed (i.i.d.) MIMO Rayleigh channel. Furthermore, in realistic conditions it is seen that MIMO-antenna selection often leads to lower mutual information than traditional MIMO with the same number of RF chains. Moreover, it is shown that when considering phase shifters with realistic losses, MIMO technique almost always outperforms beam steering technique. In the last part of the thesis a 60 GHz planar omnidirectional antenna is presented. This antenna is very suitable for communications applications since it has low profile and uses a metal layer only on one side of the substrate. Therefore, it can be manufactured easily and at very low cost. In addition, an advanced quasi full 3-D radiation pattern measurement system has been developed to evaluate probe-fed antennas. Very good measurement repeatability is reported. The radiation of the probe is analyzed and is seen to be the main limitation of the dynamic range of the measurement setup

Le Miroir historial de Jacques d’Armagnac : un monument bibliophilique pour un prince ambitieux

Lorsque Jacques d’Armagnac commande la première pièce de sa future bibliothèque, un monumental Miroir historial de près de 1 350 feuillets, il est alors au sommet de sa carrière politique, soutenu par le roi Louis XI qui a fait de lui l’un des seigneurs les plus puissants de son époque. Plus qu’un simple témoignage de son pouvoir, ce triple manuscrit nous éclaire sur la vie et les aspirations de ce personnage malmené par l’histoire. Le luxe ostentatoire de cet ouvrage se développe à travers les quelque cinq cents miniatures qui l’agrémentent. Réalisées par des enlumineurs particulièrement productifs au cours du xve siècle, les images du Miroir historial illustrent, par leur relative banalité iconographique, les méthodes de travail des ateliers de l’époque. Elles donnent cependant de précieux indices sur l’identité des différents historieurs qui y ont travaillé et relance, une fois encore, le débat sur l’attribution des images de cet immense manuscrit, un débat qui dure maintenant depuis plus d’un siècle.When Jacques d’Armagnac ordered the first piece of his coming library – a monumental Miroir historial composed of almost 1 350 folios – he is at the summit of his political career, supported by King Louis XI who turned him into the most powerful lords of his time. This triple manuscript is far more than the expression of his power ; it enlightens us as to the life and the figure, so manhandled by history, he has aspired to be. The luxury of this work is developed through five hundreds miniatures which enliven it. Made during the fifteenth century by particularly productive illuminators, pictures of this Miroir historial illustrate with some kind of banality the working method of the workshops from that time. Nevertheless, it gives important clues on the identity of the illuminators who worked on this great manuscript and reopens again the debate on the attribution of this pictures, an on-going debate for more than a century

Complex event recognition through wearable sensors

Complex events are instrumental in understanding advanced behaviours and properties of a system. They can represent more meaningful events as compared to simple events. In this thesis we propose to use wearable sensor signals to detect complex events. These signals are pertaining to the user's state and therefore allow us to understand advanced characteristics about her. We propose a hierarchical approach to detect simple events from the wearable sensors data and then build complex events on top of them. In order to address privacy concerns that rise from the use of sensitive signals, we propose to perform all the computation on device. While this ensures the privacy of the data, it poses the problem of having limited computational resources. This problem is tackled by introducing energy efficient approaches based on incremental algorithms. A second challenge is the multiple levels of noise in the process. A first level of noise concerns the raw signals that are inherently imprecise (e.g. inaccuracy in GPS readings). A second level of noise, that we call semantic noise, is present among the simple events detected. Some of these simple events can disturb the detection of complex events effectively acting as noise. We apply the hierarchical approach in two different contexts defining the two different parts of our thesis. In the first part, we present a mobile system that builds a representation of the user's life. This system is based on the episodic memory model, which is responsible for the storage and recollection of past experiences. Following the hierarchical approach, the system processes raw signals to detect simple events such as places where the user stayed a certain amount of time to perform an activity, therefore building sequences of detected activities. These activities are in turn processed to detect complex events that we call routines and that represent recurrent patterns in the life of the user. In the second part of this thesis, we focus on the detection of glycemic events for diabetes type-1 patients in a non-invasive manner. Diabetics are not able to properly regulate their glucose, leading to periods of high and low blood sugar. We leverage signals (Electrocardiogram (ECG), accelerometer, breathing rate) from a sport belt to infer such glycemic events. We propose a physiological model based on the variations of the ECG when the patient has low blood sugar, and an energy-based model that computes the current glucose level of the user based on her glucose intake, insulin intake and glucose consumption via physical activity. For both contexts, we evaluate our systems in term of accuracy by assessing wether the detected routines are meaningful, and wether the glycemic events are correctly detected, and in term of mobile performance, which confirms the fitness of our approaches for mobile computation

Laboratory measurements of the performances of the Sweeping Langmuir Probe instrument aboard the PICASSO CubeSat

The Sweeping Langmuir Probe (SLP) is one of the instruments on board the triple-unit CubeSat PICASSO, an ESA in-orbit demonstrator launched in September 2020, which is flying at about 540 km altitude. SLP comprises four small cylindrical probes mounted at the tip of the solar panels. It aims to perform in situ measurements of the plasma parameters (electron density and temperature together with ion density) and of the spacecraft potential in the ionosphere. Before the launch, the instrument, accommodated on an electrically representative PICASSO mock-up, was tested in a plasma chamber. It is shown that the traditional orbital-motion-limited collection theory used for cylindrical Langmuir probes cannot be applied directly for the interpretation of the measurements because of the limited dimensions of the probes with respect to the Debye length in the ionosphere. Nevertheless, this method can be adapted to take into account the short length of the probes. To reduce the data downlink while keeping the most important information in the current-voltage characteristics, SLP includes an on-board adaptive sweeping capability. This functionality has been validated in both the plasma chamber and in space, and it is demonstrated that with a reduced number of data points the electron retardation and electron saturation regions can be well resolved. Finally, the effect of the contamination of the probe surface, which can be a serious issue in Langmuir probe data analysis, has been investigated. If not accounted for properly, this effect could lead to substantial errors in the estimation of the electron temperature.</p

BRAMS: The Belgian RAdio Meteor Stations

In the last months, the Belgian Institute for Space Aeronomy has been developing a Belgian network for observing radio meteors using forward scattering technique. This network is called BRAMS for Belgian RAdio Meteor Stations. Two beacons emitting a circularly polarized pure sine wave toward the zenith act as the transmitters at frequencies of 49.97 and 49.99 MHz. The first one located in Dourbes (Southern Belgium) emits a constant power of 150 Watts while the one located in Ieper (Western Belgium) emits a constant power of 50 Watts. The receiving network consists of about 20 stations hosted mainly by radio amateurs. Two stations have crossed-Yagi antennas measuring horizontal and vertical polarizations of the waves reflected off meteor trails. This will enable a detailed analysis of the meteor power profiles from which physical parameters of the meteoroids can be obtained. An interferometer consisting of 5 Yagi-antennas will be installed at the site of Humain in order to determine the angular detection of one reflection point, allowing us to determine meteoroid trajectories. We describe this new meteor observing facility and present the goals we expect to achieve with the network

A study of the operative treatment for loss of nerve substance in peripheral nerves

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50233/1/1050110304_ftp.pd

A microwave transmission-line network guiding electromagnetic fields through a dense array of metallic objects

We present measurements of a transmission-line network, designed for cloaking applications in the microwave region. The network is used for channelling microwave energy through an electrically dense array of metal objects, which is basically impenetrable to the impinging electromagnetic radiation. With the designed transmission-line network the waves emitted by a source placed in an air-filled waveguide, are coupled into the network and guided through the array of metallic objects. Our goal is to illustrate the simple manufacturing, assembly, and the general feasibility of these types of cloaking devices.Comment: 6 pages, 6 figure

RoutineSense: A Mobile Sensing Framework for the Reconstruction of User Routines

Modern smartphones are powerful platforms that have become part of the everyday life for most people. Thanks to their sensing and computing capabilities, smartphones can unobtrusively identify simple user states (e.g., location, performed activity, etc.), enabling a plethora of applications that provide insights on the lifestyle of the users. In this paper, we introduce routineSense: a system for the automatic reconstruction of complex daily routines from simple user states, implemented as an incremental processing framework. Such framework combines opportunistic sensing and user feedback to discover frequent and exceptional routines that can be used to segment and aggregate multiple user activities in a timeline. We use a comprehensive dataset containing rich geographic information to assess the feasibility and performance of routineSense, showing a near threefold improvement on the current state-of-the-art

Detection of hypoglycemic events through wearable sensors

Diabetic patients are dependent on external substances to balance their blood glucose level. In order to control this level, they historically needed to sample a drop a blood from their hand and have it analyzed. Recently, other directions emerged to offer alternative ways to estimate glucose level. In this paper, we present our ongoing work on a framework for inferring semantically annotated glycemic events on the patient, which leverages mobile wearable sensors on a sport-belt