Localization with multicomponent seismic array

International audienceSeismo-volcano source localization is essential to improve our understanding of volcano systems. The lack of clear seismic wave phases prohibits the use of classical location methods. Seismic antennas composed of one-component (1C) seismometers provide a good estimate of the back-azimuth of the wavefield. The depth estimation, on the other hand, is difficult or impossible to determine. In order to determine the source location parameters (back-azimuth and depth), we extend the 1C seismic antenna approach to 3Cs. This communication discusses a high resolution location method using a 3C array survey (3C-MUSIC algorithm) with data from two seismic antennas installed on an andesitic volcano in Peru (Ubinas volcano). After introducing the 3C MUSIC processing, we evaluate the robustness of the location method on a full wavefield 3D synthetic dataset generated using a digital elevation model of Ubinas volcano and an homogeneous velocity model. Results show that the back-azimuth determined using the 3C array has a smaller error than a 1C array. Only the 3C method allows the recovery of the source depths. Finally, we applied the 3C-MUSIC to two seismic events recorded in 2009. Therefore, extending 1C arrays to 3C arrays in volcano monitoring allows a more accurate determination of the source epicenter and now an estimate for the depth

Quaternion-valued robust adaptive beamformer for electromagnetic vector-sensor arrays with worst-case constraint

A robust adaptive beamforming scheme based on two-component electromagnetic (EM) vector-sensor arrays is proposed by extending the well-known worst-case constraint into the quaternion domain. After defining the uncertainty set of the desired signal׳s quaternionic steering vector, two quaternion-valued constrained minimization problems are derived. We then reformulate them into two real-valued convex quadratic problems, which can be easily solved via the so-called second-order cone (SOC) programming method. It is also demonstrated that the proposed algorithms can be classified as a specific type of the diagonal loading scheme, in which the optimal loading factor is a function of the known level of uncertainty of the desired steering vector. Numerical simulations show that our new method can cope with the steering vector mismatch problem well, and alleviate the finite sample size effect to some extent. Besides, the proposed beamformer significantly outperforms the sample matrix inversion minimum variance distortionless response (SMI-MVDR) and the quaternion Capon (Q-Capon) beamformers in all the scenarios studied, and achieves a better performance than the traditional diagonal loading scheme, in the case of smaller sample sizes and higher SNRs

Computation Reduction for Angle of Arrival Estimation Based on Interferometer Principle

Advancement in wireless technology and the oncoming of the Internet of Things (IoT) marked an incredible growth in the wireless connectivity, ultimately concluding to a major expansion in the mobile electronics industry. Today, around 3.1 billion users are reported being connected to the internet, along with 16.3 billion mobile electronic devices. The increasing connectivity has lead to an increase in demand for mobile services, consequently, increasing demand for location services and mobility analytics. The most common location tracking or direction finding devices are found in the form of Global Positioning System (GPS) which provides location data for a client device using satellites-based lateration techniques. However, the use of the GPS is fairly limited to large distances and often tend to fail when smaller distances are concerned. This thesis aims to dive into the study of different direction finding algorithms based on angle of arrival estimation specifically pertaining to the indoor location tracking and navigation, also known as hyperlocation. The thesis will go over the main elements used in direction finding systems while looking at some of the present research done in this respective field of interest. Afterwards, the thesis will focus on a specific angle of arrival estimation algorithm which is widely being used for hyerplocation solutions and propose an alteration in the algorithm in order to achieve a faster runtime performance on weaker processors. A comparison between the accuracies will be made between the original algorithm and the suggested solution, followed by a runtime comparison on different processing units

Ocean parameter estimation with high-frequency signals using a vector sensor array

Tese de dout., Engenharia Electrónica e Telecomunicações (Processamento de Sinal), Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2012Vector sensors began to emerge in 1980s as potential competitors to omni directional pressure driven hydrophones, while their practical usage in underwater applications started in the last two decades. The crucial advantage of vector sensors relative to hydrophones is that they are able to record both the omni-directional pressure and the three vectorial components of the particle velocity. A claimed advantage of vector sensors over hydrophones is the quantity of information obtained from a single point spatial device, which potentially allows for high performance small aperture Vector Sensor Arrays (VSA). The capabilities of such small aperture VSA have captured the attention for their usage in high-frequency applications. The main contribution of this work is the understanding of the gain provided by vector sensors over hydrophones whenever ocean environmental parameter estimation is concerned. In a rst step a particle velocity-pressure joint data model is proposed and an extended VSA-based Bartlett estimator is derived. This data model and estimator, initially developed for estimating direction of arrival, are generalized for ocean parameter estimation, assuming a particle velocity capable physical model - the TRACEO model. The highlighted capabilities of the VSA are rst demonstrated for angle of arrival estimation, where a variety of spatial con gurations of hydrophone arrays are compared to that of a vertical VSA. A vertical VSA array con guration is then used for estimating geoacoustic bottom properties from short range acoustic data, using two VSA-based techniques: the generalized Bartlett estimator and the re ection coe cient estimator proposed by Harrison et al.. The proposed techniques where tested on experimental VSA data recorded in shallow water area o the Island of Kauai (Hawaii) during the MakaiEx 2005 experiment. The obtained results are comparable between techniques and inline with the expected values for that region. These results suggest that it is indeed possible to obtain reliable seabed geoacoustic properties' estimates in a frequency band of 8-14 kHz using a small aperture VSA with only a few sensors.Fundação para a Ciência e a Tecnologia (FCT

Ein Beitrag zur effizienten Richtungsschätzung mittels Antennenarrays

Sicherlich gibt es nicht den einen Algorithmus zur Schätzung der Einfallsrichtung elektromagnetischer Wellen. Statt dessen existieren Algorithmen, die darauf optimiert sind Hunderte Pfade zu finden, mit uniformen linearen oder kreisförmigen Antennen-Arrays genutzt zu werden oder möglichst schnell zu sein. Die vorliegende Dissertation befasst sich mit letzterer Art. Wir beschränken uns jedoch nicht auf den reinen Algorithmus zur Richtungsschätzung (RS), sondern gehen das Problem in verschiedener Hinsicht an. Die erste Herangehensweise befasst sich mit der Beschreibung der Array-Mannigfaltigkeit (AM). Bisherige Interpolationsverfahren der AM berücksichtigen nicht inhärent Polarisation. Daher wird separat für jede Polarisation einzeln interpoliert. Wir übernehmen den Ansatz, eine diskrete zweidimensionale Fouriertransformation (FT) zur Interpolation zu nutzen. Jedoch verschieben wir das Problem in den Raum der Quaternionen. Dort wenden wir eine zweidimensionale diskrete quaternionische FT an. Somit können beide Polarisationszustände als eine einzige Größe betrachtet werden. Das sich ergebende Signalmodell ist im Wesentlichen kompatibel mit dem herkömmlichen komplexwertigen Modell. Unsere zweite Herangehensweise zielt auf die fundamentale Eignung eines Antennen-Arrays für die RS ab. Zu diesem Zweck nutzen wir die deterministische Cramér-Rao-Schranke (Cramér-Rao Lower Bound, CRLB). Wir leiten drei verschiedene CRLBs ab, die Polarisationszustände entweder gar nicht oder als gewünschte oder störende Parameter betrachten. Darüber hinaus zeigen wir auf, wie Antennen-Arrays schon während der Design-Phase auf RS optimiert werden können. Der eigentliche Algorithmus zur RS stellt die letzte Herangehensweise dar. Mittels einer MUSIC-basierte Kostenfunktion leiten wir effiziente Schätzer ab. Hierfür kommt eine modifizierte Levenberg- bzw. Levenberg-Marquardt-Suche zum Einsatz. Da die eigentliche Kostenfunktion hier nicht angewendet werden kann, ersetzen wir diese durch vier verschiedene Funktionen, die sich lokal ähnlich verhalten. Diese Funktionen beruhen auf einer Linearisierung eines Kroneckerproduktes zweier polarimetrischer Array-Steering-Vektoren. Dabei stellt sich heraus, dass zumindest eine der Funktionen in der Regel zu sehr schneller Konvergenz führt, sodass ein echtzeitfähiger Algorithmus entsteht.It is save to say that there is no such thing as the direction finding (DF) algorithm. Rather, there are algorithms that are tuned to resolve hundreds of paths, algorithms that are designed for uniform linear arrays or uniform circular arrays, and algorithms that strive for efficiency. The doctoral thesis at hand deals with the latter type of algorithms. However, the approach taken does not only incorporate the actual DF algorithm but approaches the problem from different perspectives. The first perspective concerns the description of the array manifold. Current interpolation schemes have no notion of polarization. Hence, the array manifold interpolation is performed separately for each state of polarization. In this thesis, we adopted the idea of interpolation via a 2-D discrete Fourier transform. However, we transform the problem into the quaternionic domain. Here, a 2-D discrete quaternionic Fourier transform is applied. Hence, both states of polarization can be viewed as a single quantity. The resulting interpolation is applied to a signal model which is essentially compatible to conventional complex model. The second perspective in this thesis is to look at the fundamental DF capability of an antenna array. For that, we use the deterministic Cramér-Rao Lower Bound (CRLB). We point out the differences between not considering polarimetric parameters and taking them as desired parameters or nuisance parameters. Such differences lead to three different CRLBs. Moreover, insight is given how a CRLB can be used to optimize an antenna array already during the design process to improve its DF performance. The actual DF algorithm constitutes the third perspective that is considered in this thesis. A MUSIC-based cost function is used to derive efficient estimators. To this end, a modified Levenberg search and Levenberg-Marquardt search are employed. Since the original cost function is not eligible to be used in this framework, we replace it by four different functions that locally show the same behavior. These functions are based on a linearization of Kronecker products of two polarimetric array steering vectors. It turns out that at least one of these functions usually exhibits very fast convergence leading to real-time capable algorithms

Understanding magmatic processes and seismo-volcano source localization with multicomponent seismic arrays

Dans cette thèse, nous étudions le problème de la localisation de sources sismo-volcanique, à partir des données enregistrées par des réseaux de capteurs composés de nouveaux sismomètres à trois composantes (3C). Nous nous concentrerons sur le volcan Ubinas, l'un des plus actifs au Pérou. Nous développons une nouvelle approche (MUSIC-3C) basée sur la méthode MUSIC permetant de retourner les 3 paramètres utiles (lenteur, azimut et incidence). Pour valider notre méthodologie, nous analysons des sources synthétiques propagées en tenant compte de la topographie du volcan Ubinas. Dans cette expérience, les données synthétiques ont été générées pour plusieurs sources situées à différentes profondeurs sous le cratère Ubinas. Nous utilisons l'algorithme MUSIC-3C pour les relocaliser. Nous traitons également des données réelles provenant d'une expérience de terrain menée sur le volcan Ubinas (Pérou) en 2009 par les équipes de recherche de l'IRD-France (Institut de Recherche pour le Déveleppment), UCD l'Irlande (projet VOLUME) et l'Institut de Géophysique du Pérou (IGP). Nous utilisons l'algorithme MUSIC-3C pour localiser les événements explosifs (type vulcanien), ce qui nous permet d'identifier et d'analyser les processus physiques de ces événements, à la suite de cette analyse, nous avons trouvé deux sources pour chaque explosion situées à 300 m et 1100 m en dessous du fond du cratère actif. Basé sur les mécanismes éruptifs proposés pour d'autres volcans du même type, nous interprétons la position de ces sources ainsi que les limites du conduit éruptif impliqué dans le processus de fragmentation.In this thesis, we study the seismo-volcanic source localization using data recorded by new sensor arrays composed of three-component (3C) seismometers deployed on Ubinas stratovolcano (Peru). We develop a new framework (MUSIC-3C) of source localization method based on the well-known MUSIC algorithm. To investigate the performance of the MUSIC-3C method, we use synthetic datasets designed from eight broadband isotropic seismic sources located beneath the crater floor at different depths. The fundamental scheme of the MUSIC-3C method exploits the fact of the cross-spectral matrix of 3C array data, corresponding to the first seismic signal arrivals, provides of useful vector components (slowness, back-azimuth and incidence angle) from the seismic source. Application of the MUSIC-3C method on synthetic datasets shows the recovery of source positions. Real data used in this study was collected during seismic measurements with two seismic antennas deployed at Ubinas volcano in 2009, whose experiment conduced by volcanic teams of IRD-France (l'Institute de Recherche pour le Déveleppment), Geophysics group University College Dublin Ireland and Geophysical Institute of Peru (IGP). We apply the MUSIC-3C algorithm to investigate wave fields associated with the magmatic activity of Ubinas volcano. These analysis evidence a complex mechanism of vulcanian eruptions in which their seismic sources are found at two separated sources located at depths of 300 m and 1100 m beneath the crater floor. This implies the reproduction of similar mechanisms into the conduit. Based on the eruptive mechanisms proposed for other volcanoes of the same type, we interpret the position of this sources as the limits of the conduit portion that was involved in the fragmentation process.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Quaternion-Valued Adaptive Signal Processing and Its Applications to Adaptive Beamforming and Wind Profile Prediction

Quaternion-valued signal processing has received more and more attentions in the past ten years due to the increasing need to process three or four-dimensional signals, such as colour images, vector-sensor arrays, three-phase power systems, dual-polarisation based wireless communica- tion systems, and wind profile prediction. One key operation involved in the derivation of all kinds of adaptive signal processing algorithms is the gradient operator. Although there are some derivations of this operator in literature with different level of details in the quaternion domain, it is still not fully clear how this operator can be derived in the most general case and how it can be applied to various signal processing problems. In this study, we will give a detailed derivation of the quaternion-valued gradient operator with associated properties and then apply it to different areas. In particular, it will be employed to derive the quaternion-valued LMS (QLMS) algorithm and its sparse versions for adaptive beamforming for vector sensor arrays, and another one is its application to wind profile prediction in combination with the classic computational fluid dynamics (CFD) approach. For the adaptive beamforming problem for vector sensor arrays, we consider the crossed- dipole array and the problem of how to reduce the number of sensors involved in the adap- tive beamforming process, so that reduced system complexity and energy consumption can be achieved, whereas an acceptable performance can still be maintained, which is particularly use- ful for large array systems. The quaternion-valued steering vector model for crossed-dipole arrays will be employed, and a reweighted zero attracting (RZA) QLMS algorithm is then pro- posed by introducing a RZA term to the cost function of the original QLMS algorithm. The RZA term aims to have a closer approximation to the l0 norm so that the number of non-zero valued coefficients can be reduced more effectively in the adaptive beamforming process. For wind profile prediction, it can be considered as a signal processing problem and we can solve it using traditional linear and non-linear prediction techniques, such as the proposed QLMS algorithm and its enhanced frequency-domain multi-channel version. On the other hand,it using traditional linear and non-linear prediction techniques, such as the proposed QLMS algorithm and its enhanced frequency-domain multi-channel version. On the other hand,wind flow analysis is also a classical problem in the CFD field, which employs various simulation methods and models to calculate the speed of wind flow at different time. It is accurate but time-consuming with high computational cost. To tackle the problem, a combined approach based on synergies between the statistical signal processing approach and the CFD approach is proposed. There are different ways of combining the signal processing approach and the CFD approach to obtain a more effective and efficient method for wind profile prediction. In the combined method, the signal processing part employs the QLMS algorithm, while for the CFD part, large eddy simulation (LES) based on the Smagorinsky subgrid-scale (SGS) model will be employed so that more efficient wind profile prediction can be achieved

Low-frequency Antennas, Transparent Ground Planes, and Transponders for Communication Enhancement in Unfavorable Environments

The communication environment has a major influence on the performance of wireless networks. Unlike antennas, receivers, processors, and other components of a typical wireless system, the designer has almost no control over the communication channel. Therefore, it is imminent that the adverse effects of the communication channel such as path-loss, multi-path, lack of a clear line of sight, and interference are among the most limiting factors in designing and operating wireless networks. Recent investments in infrastructures such as cell-phone towers, communication satellites, routers, and networking devices have been aimed at reducing the aforementioned adverse effects. However, wireless ad hoc networks (WANET) cannot rely on pre-existing infrastructures such as access points or routers. In this thesis, a number of solutions are presented to enhance communication and navigation in harsh environments. 1) At lower frequencies, the defects of the communication channel are less prominent, which has led militaries to use UHF and VHF frequency bands for communication. A number of optically transparent UHF antennas are developed and embedded in the windows of military vehicles to reduce their visual signature. 2) Direction finding at low frequencies using baseline method results in an exorbitantly large array of sensors. However, a vector sensor consisting of three orthogonal two-port loop antennas can be used. A simple and accurate circuit model for the two-port loop antenna is developed for the first time that can be used for direction of arrival estimation over a wide range of frequencies and angles. 3) Using a conventional radio repeater with ad-hoc systems requires a communication protocol and decreases the throughput by a factor of two for every repeater in the chain. A full-duplex repeater, capable of simultaneously transmitting and receiving at the same frequency, is developed for the 2.4 GHz ISM band.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/143898/1/manikafa_1.pd