Tri-band CMOS Circuit Dedicated for Ambient RF Energy Harvesting

RÉSUMÉ L'utilisation de systèmes sans fil connait une croissance rapide dans divers domaines tels que les réseaux de téléphonie cellulaire, Wi-Fi, Wi-Max, la radiodiffusion et les communications par satellite. Cette croissance mènera à une quantité considérable d'énergie électromagnétique générée dans l'air ambiant, mais toujours en dessous des limites de sécurité internationales. Ainsi, la recherche au niveau des systèmes de récupération d'énergie RF pour alimenter des appareils électroniques miniaturisés à faible consommation de puissance devient attrayante et prometteuse. Le bloc principal dans un système de récupération d'énergie RF est le redresseur qui détermine l'efficacité et la sensibilité de l'ensemble du système. Étant donné que la puissance RF ambiante est très faible, la quantité d'énergie captée par l'antenne l’est également. En outre, il y a des pertes au niveau du réseau d'adaptation d’impédance qui réduisent encore plus la puissance transmise au bloc redresseur. Par conséquent, la puissance disponible est trop faible pour faire fonctionner des redresseurs classiques. Dans ce mémoire, nous proposons trois redresseurs à trois-étages et à grilles totalement croisées-couplées en utilisant des transistors à faible tension de seuil afin d’opérer à de faibles puissances d'entrée. Les trois redresseurs ont été conçus et intégrés au sein d’une même puce fabriquée en utilisant une technologie CMOS 130nm d’IBM. Ils ont été optimisés à des fréquences de 880MHz, 1960MHz et 2.45GHz respectivement. Les résultats expérimentaux démontrent qu’ils atteignent une efficacité de conversion de puissance maximale de 62%, 62% et 56.2% respectivement. Les mesures montrent également une grande amélioration de l'efficacité à de faibles niveaux de puissance d'entrée. Afin de récupérer l'énergie ambiante de trois principales sources RF au Canada – GSM-850, GSM-1900 et Wi-Fi, un système de redresseur utilisé pour la combinaison de la puissance de ces trois canaux est simulé et analysé. Le système utilise une topologie consistant simplement à connecter les sorties des redresseurs ensemble pour charger le condensateur de charge. En dépit de la grande amélioration de l'efficacité et de la sensibilité dans la plage de 0-5μW, une baisse d'efficacité indésirable se produit aux puissances plus élevées. Ainsi, un nouveau bloc de gestion de l'alimentation est proposé. De plus, une antenne tri-bande est conçue et simulée pour diminuer le volume de l'ensemble du système de récupération d'énergie RF. En particulier, les pertes par réflexion obtenues sont de -25.43dB, -13.92dB et -12.73dB aux fréquences citées plus haut respectivement.---------- ABSTRACT Nowadays, the use of wireless systems has grown rapidly in various domains such as cellular phone networks, Wi-Fi, Wi-Max, radio broadcasting and satellite communications. The growing use of these wireless systems leads to considerable amount of electromagnetic energy generated in ambient air (of course, still below international safety limits). Thus the research in ambient RF energy harvesting system dedicated for powering up low-power-consumption miniaturized electronic devices becomes attractive and promising. The main block in a RF harvesting system is the rectifier which determines the efficiency and sensitivity of the whole system. Since ambient RF power is very low, the amount of power captured by the antenna is extremely low. Besides, there is loss on matching networks, thus the available power given to the rectifier block is too low for traditional rectifiers to operate. Therefore, in this master thesis, three three-stage fully gate cross-coupled rectifiers using low-thresholdvoltage transistors are proposed to overcome the dead zone in low input power range. The three rectifiers optimized at 880MHz, 1960MHz and 2.45GHz frequencies respectively are designed on one chip layout. Their experimental results are retrieved from this custom fabricated integrated circuit using IBM 130nm CMOS technology. They achieve peak efficiencies of 62%, 62% and 56.2% respectively and show great improvements on power conversion efficiency at low input power level. In order to harvest ambient RF energy from the three main RF contributors in Canada – GSM-850, GSM-1900 and Wi-Fi 2.4GHz, a rectifier system used for power combination from these three channels is simulated and analyzed. The system employs a simple topology by connecting the outputs together to charge the load capacitor. In spite of its high improvements on efficiency and sensitivity in 0-5μW range, an undesirable efficiency drop happens at higher input power levels. Thus an idea of power management block is proposed. In addition, a tri-band antenna is designed and simulated so as to decrease the volume of the overall RF energy harvesting system. It achieves return loss of -25.43dB, -13.92dB and - 12.73dB at each desired band respectively

Accretion-modified stellar-mass black hole distribution and milli-Hz gravitational wave backgrounds from galaxy centre

Gas accretion of embedded stellar-mass black holes\,(sBHs) or stars in the accretion disk of active galactic nuclei\,(AGNs) will modify the mass distribution of these sBHs and stars, which will also affect the migration of the sBHs/stars. With the introduction of the mass accretion effect, we simulate the evolution of the sBH/star distribution function in a consistent way by extending the Fokker-Planck equation of sBH/star distributions to the mass-varying scenario, and explore the mass distribution of sBHs in the nuclear region of the galaxy centre. We find that the sBHs can grow up to several tens solar mass and form heavier sBH binaries, which will be helpful for us to understand the black-hole mass distribution as observed by the current and future ground-based gravitational wave detectors\,(e.g., LIGO/VIRGO, ET and Cosmic Explorer). We further estimate the event rate of extreme mass-ratio inspirals\,(EMRI) for sBH surrounding the massive black hole and calculate the stochastic gravitational wave\,(GW) background of the EMRIs. We find that the background can be detected in future space-borne GW detectors after considering the sBHs embedded in the AGN disk, while the mass accretion has a slight effect on the GW background.Comment: 15 pages, 8 figures, Accepted by MNRA

Motion of Cesium Atoms in the One-Dimensional Magneto-Optical Trap

The force to which Cs atoms are subjected in the one-dimensional magneto-optical trap (lD-MOT) is calculated, and properties of this force are discussed. Several methods to increase the number of Cs atoms in the lD-MOT are presented on the basis of the analysis of the capture and escape of Cs atoms in the ID-MOT

ON THE SPECTRAL INSTABILITY AND BIFURCATION OF 2D-QUASI-GEOSTROPHIC POTENTIAL VORTICITY EQUATION

The analysis on hydrodynamic stability of shear flows is an active research direction in fluid dynamics. In this article, the spectral instability and bifurcation of forced shear flows governed by the 2D quasi-geostrophic equation with a generalized Kolmogorov forcing are investigated. We prove that the corresponding eigenvalue problem can be transferred into a family of algebraic equations with infinity number of variables, and the nontrivial solutions to the algebraic equations are expressed in form of continuous fractions. After obtaining the asymptotic estimate for the ratio of the imaginary parts of eigenvalues to a control parameter R as it approaches to infinity, we show that there exists a critical value Rc above which, the forced shear flows become unstable, where the control parameter R is the product of Reynolds number Re and the intensity of the curl of the forcing. To shed light on the bifurcation involved in the losing stability of the forced shear flows, a natural method used to reduce the quasi-geostrophic equation to ODEs is introduced. Based on numerical experiments on the coefficients in the ODEs, we show that both supercritical and subcritical Hopf bifurcations occur in the forced shear flows, which only depend on the type of generalized Kolmogorov forcing

A Parallel Batch-Dynamic Data Structure for the Closest Pair Problem

We propose a theoretically-efficient and practical parallel batch-dynamic data structure for the closest pair problem. Our solution is based on a serial dynamic closest pair data structure by Golin et al., and supports batches of insertions and deletions in parallel. For a data set of size $n$, our data structure supports a batch of insertions or deletions of size $m$ in $O(m(1+\log ((n+m)/m)))$ expected work and $O(\log (n+m)\log^*(n+m))$ depth with high probability, and takes linear space. The key techniques for achieving these bounds are a new work-efficient parallel batch-dynamic binary heap, and careful management of the computation across sets of points to minimize work and depth. We provide an optimized multicore implementation of our data structure using dynamic hash tables, parallel heaps, and dynamic $k$-d trees. Our experiments on a variety of synthetic and real-world data sets show that it achieves a parallel speedup of up to 38.57x (15.10x on average) on 48 cores with hyper-threading. In addition, we also implement and compare four parallel algorithms for static closest pair problem, for which we are not aware of any existing practical implementations. On 48 cores with hyper-threading, the static algorithms achieve up to 51.45x (29.42x on average) speedup, and Rabin's algorithm performs the best on average. Comparing our dynamic algorithm to the fastest static algorithm, we find that it is advantageous to use the dynamic algorithm for batch sizes of up to 20\% of the data set. As far as we know, our work is the first to experimentally evaluate parallel closest pair algorithms, in both the static and the dynamic settings

On the noise effect of test mass surface roughness in spaceborne gravitational wave detectors

Spaceborne gravitational wave detection mission has a demanding requirement for the precision of displacement sensing, which is conducted by the interaction between the laser field and test mass. However, due to the roughness of the reflecting surface of the test mass, the displacement measurement along the sensitive axis suffers a coupling error caused by the residue motion of other degrees of freedom. In this article, we model the coupling of the test mass residue random motion to the displacement sensing along the sensitive axis and derived an analytical formula of the required precision of the surface error for the spaceborne gravitational wave detectors. Our result shows that this coupling error will not contaminate the picometer displacement sensing for the test masses in the LISA pathfinder.Comment: 8 page

Terahertz Artificial Dielectric Lens

We have designed, fabricated, and experimentally characterized a lens for the THz regime based on artificial dielectrics. These are man-made media that mimic properties of naturally occurring dielectric media, or even manifest properties that cannot generally occur in nature. For example, the well-known dielectric property, the refractive index, which usually has a value greater than unity, can have a value less than unity in an artificial dielectric. For our lens, the artificial-dielectric medium is made up of a parallel stack of 100 μm thick metal plates that form an array of parallel-plate waveguides. The convergent lens has a plano-concave geometry, in contrast to conventional dielectric lenses. Our results demonstrate that this lens is capable of focusing a 2 cm diameter beam to a spot size of 4 mm, at the design frequency of 0.17 THz. The results further demonstrate that the overall power transmission of the lens can be better than certain conventional dielectric lenses commonly used in the THz regime. Intriguingly, we also observe that under certain conditions, the lens boundary demarcated by the discontinuous plate edges actually resembles a smooth continuous surface. These results highlight the importance of this artificial-dielectric technology for the development of future THz-wave devices

Probing phase transition in neutron stars via the crust-core interfacial mode

Gravitational waves emitted from the binary neutron star (BNS) systems can carry information about the dense matter phase in these compact stars. The crust-core interfacial mode is an oscillation mode in a neutron star and it depends mostly on the equation of the state of the matter in the crust-core transition region. This mode can be resonantly excited by the tidal field of an inspiraling-in BNS system, thereby affecting the emitted gravitational waves, and hence could be used to probe the equation of state in the crust-core transition region. In this work, we investigate in detail how the first-order phase transition inside the neutron star affects the properties of the crust-core interfacial mode, using a Newtonian fluid perturbation theory on a general relativistic background solution of the stellar structure. Two possible types of phase transitions are considered: (1) the phase transitions happen in the fluid core but near the crust-core interface, which results in density discontinuities; and (2) the strong interaction phase transitions in the dense core (as in the conventional hybrid star case). These phase transitions' impacts on interfacial mode properties are discussed. In particular, the former phase transition has a minor effect on the M-R relation and the adiabatic tidal deformability, but can significantly affect the interfacial mode frequency and thereby could be probed using gravitational waves. For the BNS systems, we discuss the possible observational signatures of these phase transitions in the gravitational waveforms and their detectability. Our work enriches the exploration of the physical properties of the crust-core interfacial mode and provides a promising method for probing the phase transition using the seismology of a compact star.Comment: 18 pages, 14 figure