379 research outputs found

    A novel quaternion linear matrix equation solver through zeroing neural networks with applications to acoustic source tracking

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    Due to its significance in science and engineering, time-varying linear matrix equation (LME) problems have received a lot of attention from scholars. It is for this reason that the issue of finding the minimum-norm least-squares solution of the time-varying quaternion LME (ML-TQ-LME) is addressed in this study. This is accomplished using the zeroing neural network (ZNN) technique, which has achieved considerable success in tackling time-varying issues. In light of that, two new ZNN models are introduced to solve the ML-TQ-LME problem for time-varying quaternion matrices of arbitrary dimension. Two simulation experiments and two practical acoustic source tracking applications show that the models function superbly

    Exploiting Redundancy for UWB Anomaly Detection in Infrastructure-Free Multi-Robot Relative Localization

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    Ultra-wideband (UWB) localization methods have emerged as a cost-effective and accurate solution for GNSS-denied environments. There is a significant amount of previous research in terms of resilience of UWB ranging, with non-line-of-sight and multipath detection methods. However, little attention has been paid to resilience against disturbances in relative localization systems involving multiple nodes. This paper presents an approach to detecting range anomalies in UWB ranging measurements from the perspective of multi-robot cooperative localization. We introduce an approach to exploiting redundancy for relative localization in multi-robot systems, where the position of each node is calculated using different subsets of available data. This enables us to effectively identify nodes that present ranging anomalies and eliminate their effect within the cooperative localization scheme. We analyze anomalies created by timing errors in the ranging process, e.g., owing to malfunctioning hardware. However, our method is generic and can be extended to other types of ranging anomalies. Our approach results in a more resilient cooperative localization framework with a negligible impact in terms of the computational workload

    Ultra-Wideband Trained Artificial Neural Networks for Bluetooth Proximity Detection in Small Crowded Areas

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    Estimating the distance between indoor users is increasingly important in unexpected ways. One specific example is the need for electronic contact tracing demonstrated during the recent global pandemic. Smartphones are now routinely equipped with Bluetooth Low Energy radios, among other sensors, and these can be used for proximity detection based on received signal strength that is subject to errors due to poor modelling of the indoor propagation environment. Some high-end smartphones have now also been equipped with ultra-wideband ranging radios that provide a much more precise range measurement. This thesis demonstrates the concept of using a limited number of UWB-equipped smartphones to gather data to train Artificial Neural Networks (ANN) to improve short-range distance estimation among Bluetooth users. The trained RSSI to range model can be used for proximity determination by other Bluetooth users in small, crowded areas. Two ANN algorithms were trained using RSSI measurements from three BLE advertising channels and UWB range as ground truth and training data. The initial training and testing were conducted in a semi-empty office laboratory with 2130 observations. The RF model used 1917 samples (90% of data) for training and 213 samples (10%) for testing, while the CNN method used 1704 samples (80% of data) for training and 426 samples (20%) for evaluation. The trained neural network models were tested in two other office environments under different user conditions. The results indicate that the ANN models can estimate proximity in a new environment without further training with a mean error of less than 1.2 metres, within a range of up to 6 metres at line-of-sight (LOS). In highly constrained non-line-of-sight (NLOS) areas in the first office room, the proposed models provided proximity accuracy better than 2.9 metres. Furthermore, during testing across two adjacent office environments, each containing a single BLE device with complex furniture arrangements, the ANN models showed the proximity between the BLE devices with an error of less than 2-3 metres

    Localizability Optimization for Multi Robot Systems and Applications to Ultra-Wide Band Positioning

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    RÉSUMÉ: RÉSUMÉ Les Systèmes Multi-Robots (SMR) permettent d’effectuer des missions de manière efficace et robuste du fait de leur redondance. Cependant, les robots étant des véhicules autonomes, ils nécessitent un positionnement précis en temps réel. Les techniques de localisation qui utilisent des Mesures Relatives (MR) entre les robots, pouvant être des distances ou des angles, sont particulièrement adaptées puisqu’elles peuvent bénéficier d’algorithmes coopératifs au sein du SMR afin d’améliorer la précision pour l’ensemble des robots. Dans cette thèse, nous proposons des stratégies pour améliorer la localisabilité des SMR, qui est fonction de deux facteurs. Premièrement, la géométrie du SMR influence fondamentalement la qualité de son positionnement pour des MR bruitées. Deuxièmement, les erreurs de mesures dépendent fortement de la technologie utilisée. Dans nos expériences, nous nous focalisons sur la technologie UWB (Ultra-Wide Band), qui est populaire pour le positionnement des robots en environnement intérieur en raison de son coût modéré et sa haute précision. Par conséquent, une partie de notre travail est consacrée à la correction des erreurs de mesure UWB afin de fournir un système de navigation opérationnel. En particulier, nous proposons une méthode de calibration des biais systématiques et un algorithme d’atténuation des trajets multiples pour les mesures de distance en milieu intérieur. Ensuite, nous proposons des Fonctions de Coût de Localisabilité (FCL) pour caractériser la géométrie du SMR, et sa capacité à se localiser. Pour cela, nous utilisons la Borne Inférieure de Cramér-Rao (BICR) en vue de quantifier les incertitudes de positionnement. Par la suite, nous fournissons des schémas d’optimisation décentralisés pour les FCL sous l’hypothèse de MR gaussiennes ou log-normales. En effet, puisque le SMR peut se déplacer, certains de ses robots peuvent être déployés afin de minimiser la FCL. Cependant, l’optimisation de la localisabilité doit être décentralisée pour être adaptée à des SMRs à grande échelle. Nous proposons également des extensions des FCL à des scénarios où les robots embarquent plusieurs capteurs, où les mesures se dégradent avec la distance, ou encore où des informations préalables sur la localisation des robots sont disponibles, permettant d’utiliser la BICR bayésienne. Ce dernier résultat est appliqué au placement d’ancres statiques connaissant la distribution statistique des MR et au maintien de la localisabilité des robots qui se localisent par filtrage de Kalman. Les contributions théoriques de notre travail ont été validées à la fois par des simulations à grande échelle et des expériences utilisant des SMR terrestres. Ce manuscrit est rédigé par publication, il est constitué de quatre articles évalués par des pairs et d’un chapitre supplémentaire. ABSTRACT: ABSTRACT Multi-Robot Systems (MRS) are increasingly interesting to perform tasks eÿciently and robustly. However, since the robots are autonomous vehicles, they require accurate real-time positioning. Localization techniques that use relative measurements (RMs), i.e., distances or angles, between the robots are particularly suitable because they can take advantage of cooperative schemes within the MRS in order to enhance the precision of its positioning. In this thesis, we propose strategies to improve the localizability of the SMR, which is a function of two factors. First, the geometry of the MRS fundamentally influences the quality of its positioning under noisy RMs. Second, the measurement errors are strongly influenced by the technology chosen to gather the RMs. In our experiments, we focus on the Ultra-Wide Band (UWB) technology, which is popular for indoor robot positioning because of its mod-erate cost and high accuracy. Therefore, one part of our work is dedicated to correcting the UWB measurement errors in order to provide an operable navigation system. In particular, we propose a calibration method for systematic biases and a multi-path mitigation algorithm for indoor distance measurements. Then, we propose Localizability Cost Functions (LCF) to characterize the MRS’s geometry, using the Cramér-Rao Lower Bound (CRLB) as a proxy to quantify the positioning uncertainties. Subsequently, we provide decentralized optimization schemes for the LCF under an assumption of Gaussian or Log-Normal RMs. Indeed, since the MRS can move, some of its robots can be deployed in order to decrease the LCF. However, the optimization of the localizability must be decentralized for large-scale MRS. We also propose extensions of LCFs to scenarios where robots carry multiple sensors, where the RMs deteriorate with distance, and finally, where prior information on the robots’ localization is available, allowing the use of the Bayesian CRLB. The latter result is applied to static anchor placement knowing the statistical distribution of the MRS and localizability maintenance of robots using Kalman filtering. The theoretical contributions of our work have been validated both through large-scale simulations and experiments using ground MRS. This manuscript is written by publication, it contains four peer-reviewed articles and an additional chapter

    Hybrid UWB-Inertial TDoA-based Target Tracking with Concentrated Anchors

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    In this paper, hybrid radio/inertial mobile target tracking for accurate and smooth path estimation is considered. The proposed tracking approach builds upon an Ultra WideBand (UWB)-based positioning algorithm, based on the Linear Hyperbolic Positioning System (LinHPS), with Time Difference of Arrival (TDoA) processing and anchors concentrated on a single hotspot at the center of the environment where the target moves. First, we design an Adaptive Radio-based Extended Kalman Filter (AREKF), which does not require a priori statistical knowledge of the noise in the target movement model and estimates the measurement noise covariance, at each sampling time, according to a proper LookUp Table (LUT). In order to improve the performance of AREKF, we incorporate inertial data collected from the target and propose three “hybrid” radio/inertial algorithms, denoted as Hybrid Inertial Measurement Unit (IMU)-aided Radio-based EKF (HIREKF), Hybrid Noisy Control EKF (HNCEKF), and Hybrid Control EKF (HCEKF). Our results on experimentally acquired paths show that the proposed algorithms achieve an average instantaneous position estimation error on the order of a few centimeters. Moreover, the minimum target path length estimation error, obtained with HCEKF, is on the order of 6% and 1% for two paths with lengths equal to approximately 17 m and 46 m, respectively

    Využití softwarově definovaného rádia v oblasti SMART technologii

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    Modern telecommunication systems are rapidly evolving. This rapid development requires constant research and fast prototyping. This dissertation thesis focusses on deployment of software defined radio (SDR) in multiple application areas, including SMART technologies. SDR itself is a tool behind many breakthroughs in modern telecommunications, due to its major adaptability. It offers a comprehensive way of fast prototyping, which rely on suitable software platform. The field of telecommunications is ever-changing, due to the constant pressure on innovation. For this reason, it is desirable to test some of the alternative communication technologies. Visible light communication (VLC) system based on combination of virtual instrumentation and software defined radios was chosen for experimentation. This dissertation focusses on multiple versions of VLC system that were developed over the years. Each version is further discussed, and their advantages and disadvantages are presented. A draft of fourth and newest version is mentioned along with possible directions of the research. Results from multiple application areas are presented, which show the adaptability of the whole platform to different use cases including but not limited to: SMART technologies, automotive, nuclear waste disposal sites, or industry. It is demonstrated that the newest version of the system, which is based on OFDM modulation, can communicate up to 50 meters in closed environments and up to 35 meters in outdoor scenarios. This opens further research directions such as truck platooning or underwater communications.Moderní komunikační systémy jsou jednou z nejrychleji se rozvíjejících oblastí. Takového markantního posunu lze dosáhnout pouze skrze nový vývoj a aplikaci metodiky fast prototypingu. Tato disertace se zaměřuje na nasazení technologie softwarově definovaného rádia (SDR) v různých aplikačních oblastech. Samotné SDR je díky své adaptabilitě nástrojem, který stál na pozadí rozvoje mnoha moderních telekomunikačních systémů. Jedná se o ucelenou platformu pro fast prototyping, která se opírá o robustní softwarovou základnu. Právě telekomunikace jsou oblastí, kde je takové zařízení nedocenitelné, právě kvůli neustálému tlaku na inovace. Právě to je důvodem, proč je vhodné také testovat různé alternativní technologie pro přenos dat. Jednou z takových je komunikace viditelným spektrem světla (VLC), která je náplní této práce. Součástí praktické části je vývoj a popis několika verzí VLC systému založených na virtuální instrumentaci a SDR, které vznikly během autorova studia. Každá verze je samostatně popsána včetně výhod a nevýhod, které poskytují. Součástí je též první náčrt čtvrté verze, která bude součástí budoucího výzkumu. Prezentované výsledky z různých aplikačních oblastí jasně ukazují, že je celou platformu možné použít v různých aplikačních oblastech, včetně SMART technologií, automotive, úložišti jaderného odpadu anebo Průmyslu 4.0. Součástí jsou též výsledky z poslední verze, které dokazují, že je systém ve vnitřních prostorech komunikovat až na vzdálenost 50 metrů, zatímco ve venkovních podmínkách je to 35 metrů. Díky tomu je možné vytyčit nové oblasti výzkumu jako je například platooning (tandemová jízda) anebo podvodní komunikace.450 - Katedra kybernetiky a biomedicínského inženýrstvívyhově

    BLE-based Indoor Localization and Contact Tracing Approaches

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    Internet of Things (IoT) has penetrated different aspects of modern life with smart sensors being prevalent within our surrounding indoor environments. Furthermore, dependence on IoT-based Contact Tracing (CT) models has significantly increased mainly due to the COVID-19 pandemic. There is, therefore, an urgent quest to develop/design efficient, autonomous, trustworthy, and secure indoor CT solutions leveraging accurate indoor localization/tracking approaches. In this context, the first objective of this Ph.D. thesis is to enhance accuracy of Bluetooth Low Energy (BLE)-based indoor localization. BLE-based localization is typically performed based on the Received Signal Strength Indicator (RSSI). Extreme fluctuations of the RSSI occurring due to different factors such as multi-path effects and noise, however, prevent the BLE technology to be a reliable solution with acceptable accuracy for dynamic tracking/localization in indoor environments. In this regard, first, an IoT dataset is constructed based on multiple thoroughly separated indoor environments to incorporate the effects of various interferences faced in different spaces. The constructed dataset is then used to develop a Reinforcement Learning (RL)-based information fusion strategy to form a multiple-model implementation consisting of RSSI, Pedestrian dead reckoning (PDR), and Angle-of-Arrival (AoA)-based models. In the second part of the thesis, the focus is devoted to application of multi-agent Deep Neural Networks (DNN) models for indoor tracking. DNN-based approaches are, however, prone to overfitting and high sensitivity to parameter selection, which results in sample inefficiency. Moreover, data labelling is a time-consuming and costly procedure. To address these issues, we leverage Successor Representations (SR)-based techniques, which can learn the expected discounted future state occupancy, and the immediate reward of each state. A Deep Multi-Agent Successor Representation framework is proposed that can adapt quickly to the changes in a multi-agent environment faster than the Model-Free (MF) RL methods and with a lower computational cost compared to Model-Based (MB) RL algorithms. In the third part of the thesis, the developed indoor localization techniques are utilized to design a novel indoor CT solution, referred to as the Trustworthy Blockchain-enabled system for Indoor Contact Tracing (TB-ICT) framework. The TB-ICT is a fully distributed and innovative blockchain platform exploiting the proposed dynamic Proof of Work (dPoW) approach coupled with a Randomized Hash Window (W-Hash) and dynamic Proof of Credit (dPoC) mechanisms

    Analysis and Design of Silicon based Integrated Circuits for Radio Frequency Identification and Ranging Systems at 24GHz and 60GHz Frequency Bands

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    This scientific research work presents the analysis and design of radio frequency (RF) integrated circuits (ICs) designed for two cooperative RF identification (RFID) proof of concept systems. The first system concept is based on localizable and sensor-enabled superregenerative transponders (SRTs) interrogated using a 24GHz linear frequency modulated continuous wave (LFMCW) secondary radar. The second system concept focuses on low power components for a 60GHz continuous wave (CW) integrated single antenna frontend for interrogating close range passive backscatter transponders (PBTs). In the 24GHz localizable SRT based system, a LFMCW interrogating radar sends a RF chirp signal to interrogate SRTs based on custom superregenerative amplifier (SRA) ICs. The SRTs receive the chirp and transmit it back with phase coherent amplification. The distance to the SRTs are then estimated using the round trip time of flight method. Joint data transfer from the SRT to the interrogator is enabled by a novel SRA quench frequency shift keying (SQ-FSK) based low data rate simplex communication. The SRTs are also designed to be roll invariant using bandwidth enhanced microstrip patch antennas. Theoretical analysis is done to derive expressions as a function of system parameters including the minimum SRA gain required for attaining a defined range and equations for the maximum number of symbols that can be transmitted in data transfer mode. Analysis of the dependency of quench pulse characteristics during data transfer shows that the duty cycle has to be varied while keeping the on-time constant to reduce ranging errors. Also the worsening of ranging precision at longer distances is predicted based on the non-idealities resulting from LFMCWchirp quantization due to SRT characteristics and is corroborated by system level measurements. In order to prove the system concept and study the semiconductor technology dependent factors, variants of 24GHz SRA ICs are designed in a 130nm silicon germanium (SiGe) bipolar complementary metal oxide technology (BiCMOS) and a partially depleted silicon on insulator (SOI) technology. Among the SRA ICs designed, the SiGe-BiCMOS ICs feature a novel quench pulse shaping concept to simultaneously improve the output power and minimum detectable input power. A direct antenna drive SRA IC based on a novel stacked transistor cross-coupled oscillator topology employing this concept exhibit one of the best reported combinations of minimum detected input power level of −100 dBm and output power level of 5.6 dBm, post wirebonding. The SiGe stacked transistor with base feedback capacitance topology employed in this design is analyzed to derive parameters including the SRA loop gain for design optimization. Other theoretical contributions include the analysis of the novel integrated quench pulse shaping circuit and formulas derived for output voltage swing taking bondwire losses into account. Another SiGe design variant is the buffered antenna drive SRA IC having a measured minimum detected input power level better than −80 dBm, and an output power level greater than 3.2 dBm after wirebonding. The two inputs and outputs of this IC also enables the design of roll invariant SRTs. Laboratory based ranging experiments done to test the concepts and theoretical considerations show a maximum measured distance of 77m while transferring data at the rate of 0.5 symbols per second using SQ-FSK. For distances less than 10m, the characterized accuracy is better than 11 cm and the precision is better than 2.4 cm. The combination of the maximum range, precision and accuracy are one of the best reported among similar works in literature to the author’s knowledge. In the 60GHz close range CW interrogator based system, the RF frontend transmits a continuous wave signal through the transmit path of a quasi circulator (QC) interfaced to an antenna to interrogate a PBT. The backscatter is received using the same antenna interfaced to the QC. The received signal is then amplified and downconverted for further processing. To prove this concept, two optimized QC ICs and a downconversion mixer IC are designed in a 22nm fully depleted SOI technology. The first QC is the transmission lines based QC which consumes a power of 5.4mW, operates at a frequency range from 56GHz to 64GHz and occupies an area of 0.49mm2. The transmit path loss is 5.7 dB, receive path gain is 2 dB and the tunable transmit path to receive path isolation is between 20 dB and 32 dB. The second QC is based on lumped elements, and operates in a relatively narrow bandwidth from 59.6GHz to 61.5GHz, has a gain of 8.5 dB and provides a tunable isolation better than 20 dB between the transmit and receive paths. This QC design also occupies a small area of 0.34mm² while consuming 13.2mW power. The downconversion is realized using a novel folded switching stage down conversion mixer (FSSDM) topology optimized to achieve one of the best reported combination of maximum voltage conversion gain of 21.5 dB, a factor of 2.5 higher than reported state-of-the-art results, and low power consumption of 5.25mW. The design also employs a unique back-gate tunable intermediate frequency output stage using which a gain tuning range of 5.5 dB is attained. Theoretical analysis of the FSSDM topology is performed and equations for the RF input stage transconductance, bandwidth, voltage conversion gain and gain tuning are derived. A feasibility study for the components of the 60GHz integrated single antenna interrogator frontend is also performed using PBTs to prove the system design concept.:1 Introduction 1 1.1 Motivation and Related Work . . . . . . . . . . . . . . . . . . . . . 1 1.2 Scope and Functional Specifications . . . . . . . . . . . . . . . . . 4 1.3 Objectives and Structure . . . . . . . . . . . . . . . . . . . . . . . . 5 2 Features and Fundamentals of RFIDs and Superregenerative Amplifiers 9 2.1 RFID Transponder Technology . . . . . . . . . . . . . . . . . . . . 9 2.1.1 Chipless RFID Transponders . . . . . . . . . . . . . . . . . 10 2.1.2 Semiconductor based RFID Transponders . . . . . . . . . . 11 2.1.2.1 Passive Transponders . . . . . . . . . . . . . . . . 11 2.1.2.2 Active Transponders . . . . . . . . . . . . . . . . . 13 2.2 RFID Interrogator Architectures . . . . . . . . . . . . . . . . . . . 18 2.2.1 Interferometer based Interrogator . . . . . . . . . . . . . . . 19 2.2.2 Ultra-wideband Interrogator . . . . . . . . . . . . . . . . . . 20 2.2.3 Continuous Wave Interrogators . . . . . . . . . . . . . . . . 21 2.3 Coupling Dependent Range and Operating Frequencies . . . . . . . 25 2.4 RFID Ranging Techniques . . . . . . . . . . . . . . . . . . . . . . . 28 2.4.0.1 Received Signal Strength based Ranging . . . . . 28 2.4.0.2 Phase based Ranging . . . . . . . . . . . . . . . . 30 2.4.0.3 Time based Ranging . . . . . . . . . . . . . . . . . 30 2.5 Architecture Selection for Proof of Concept Systems . . . . . . . . 32 2.6 Superregenerative Amplifier (SRA) . . . . . . . . . . . . . . . . . . 35 2.6.1 Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . 35 2.6.2 Modes of Operation . . . . . . . . . . . . . . . . . . . . . . 42 2.6.3 Frequency Domain Characteristics . . . . . . . . . . . . . . 45 2.7 Semiconductor Technologies for RFIC Design . . . . . . . . . . . . 48 2.7.1 Silicon Germanium BiCMOS . . . . . . . . . . . . . . . . . 48 2.7.2 Silicon-on-Insulator . . . . . . . . . . . . . . . . . . . . . . . 48 3 24GHz Superregenerative Transponder based Identification and Rang- ing System 51 3.1 System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.1.1 SRT Identification and Ranging . . . . . . . . . . . . . . . . 51 3.1.2 Power Link Analysis . . . . . . . . . . . . . . . . . . . . . . 55 3.1.3 Non-idealities . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3.1.4 SRA Quench Frequency Shift Keying for data transfer . . . 61 3.1.5 Knowledge Gained . . . . . . . . . . . . . . . . . . . . . . . 63 3.2 RFIC Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 3.2.1 Low Power Direct Antenna Drive CMOS SRA IC . . . . . . 66 3.2.1.1 Circuit analysis and design . . . . . . . . . . . . . 66 3.2.1.2 Characterization . . . . . . . . . . . . . . . . . . . 69 3.2.2 Direct Antenna Drive SiGe SRA ICs . . . . . . . . . . . . . 71 3.2.2.1 Stacked Transistor Cross-coupled Quenchable Oscillator . . . . . . . . . . . . . . . . . . . . . . . . 72 3.2.2.1.1 Resonator . . . . . . . . . . . . . . . . . . 72 3.2.2.1.2 Output Network . . . . . . . . . . . . . . 75 3.2.2.1.3 Stacked Transistor Cross-coupled Pair and Loop Gain . . . . . . . . . . . . . . . . . 77 3.2.2.2 Quench Waveform Design . . . . . . . . . . . . . . 85 3.2.2.3 Characterization . . . . . . . . . . . . . . . . . . . 89 3.2.3 Antenna Diversity SiGe SRA IC with Integrated Quench Pulse Shaping . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.2.3.1 Circuit Analysis and Design . . . . . . . . . . . . 91 3.2.3.1.1 Crosscoupled Pair and Sampling Current 94 3.2.3.1.2 Common Base Input Stage . . . . . . . . 95 3.2.3.1.3 Cascode Output Stage . . . . . . . . . . . 96 3.2.3.1.4 Quench Pulse Shaping Circuit . . . . . . 96 3.2.3.1.5 Power Gain . . . . . . . . . . . . . . . . . 99 3.2.3.2 Characterization . . . . . . . . . . . . . . . . . . . 102 3.2.4 Knowledge Gained . . . . . . . . . . . . . . . . . . . . . . . 103 3.3 Proof of Principle System Implementation . . . . . . . . . . . . . . 106 3.3.1 Superregenerative Transponders . . . . . . . . . . . . . . . 106 3.3.1.1 Bandwidth Enhanced Microstrip Patch Antennas 108 3.3.2 FMCW Radar Interrogator . . . . . . . . . . . . . . . . . . 114 3.3.3 Chirp Z-transform Based Data Analysis . . . . . . . . . . . 116 4 60GHz Single Antenna RFID Interrogator based Identification System 121 4.1 System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 4.2 RFIC Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 4.2.1 Quasi-circulator ICs . . . . . . . . . . . . . . . . . . . . . . 125 4.2.1.1 Transmission Lines based Quasi-Circulator IC . . 126 4.2.1.2 Lumped Elements WPD based Quasi-Circulator . 130 4.2.1.3 Characterization . . . . . . . . . . . . . . . . . . . 134 4.2.1.4 Knowledge Gained . . . . . . . . . . . . . . . . . . 135 4.2.2 Folded Switching Stage Downconversion Mixer IC . . . . . 138 4.2.2.1 FSSDM Circuit Design . . . . . . . . . . . . . . . 138 4.2.2.2 Cascode Transconductance Stage . . . . . . . . . . 138 4.2.2.3 Folded Switching Stage with LC DC Feed . . . . . 142 4.2.2.4 LO Balun . . . . . . . . . . . . . . . . . . . . . . . 145 4.2.2.5 Backgate Tunable IF Stage and Offset Correction 146 4.2.2.6 Voltage Conversion Gain . . . . . . . . . . . . . . 147 4.2.2.7 Characterization . . . . . . . . . . . . . . . . . . . 150 4.2.2.8 Knowledge Gained . . . . . . . . . . . . . . . . . . 151 4.3 Proof of Principle System Implementation . . . . . . . . . . . . . . 154 5 Experimental Tests 157 5.1 24GHz System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 5.1.1 Ranging Experiments . . . . . . . . . . . . . . . . . . . . . 157 5.1.2 Roll Invariance Experiments . . . . . . . . . . . . . . . . . . 158 5.1.3 Joint Ranging and Data Transfer Experiments . . . . . . . 158 5.2 60GHz System Detection Experiments . . . . . . . . . . . . . . . . 165 6 Summary and Future Work 167 Appendices 171 A Derivation of Parameters for CB Amplifier with Base Feedback Capac- itance 173 B Definitions 177 C 24GHz Experiment Setups 179 D 60 GHz Experiment Setups 183 References 185 List of Original Publications 203 List of Abbreviations 207 List of Symbols 213 List of Figures 215 List of Tables 223 Curriculum Vitae 22

    BLoB: Beating-based Localization for Single-antenna BLE Devices

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    Low-power wireless communication protocols based on synchronous transmissions have recently gained popularity. In such protocols, packets can be demodulated correctly even though several devices transmit at the same time, which results in high reliability and energy efficiency. A by-product of synchronous transmissions is the beating effect: a sinusoidal pattern of constructive and destructive interference across the received signal. In this paper, we leverage this beating to propose a new localization approach. Specifically, we present BLoB, a system in which multiple anchors transmit packets synchronously using the constant tone extension, an optional bit sequence introduced by BLE 5.1, whose signal is sent with constant amplitude and frequency. We let mobile tags sample the superimposed signal resulting from the synchronous transmissions, and extract peaks in the beating and signal spectrum. These peaks provide key insights about the anchors’ location that complement received signal strength information and allow BLoB to derive a tag’s position with sub-meter accuracy. A key property of BLoB is that both anchors and tags employ a single antenna, in contrast to state-of-the-art localization schemes based on angle of arrival/departure information that require costly and bulky antenna arrays to achieve sub-meter accuracy. We implement BLoB on off-the-shelf BLE devices and evaluate its performance experimentally in both static and mobile settings, and in different environments: office rooms, library, meeting room, and sports hall. Our results show that BLoB can distinguish several anchors in a single synchronous transmission and that it retains a sub-meter localization accuracy even in challenging indoor environments

    Analysis of synchronous localization systems for UAVs urban applications

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    [EN] Unmanned-Aerial-Vehicles (UAVs) represent an active research topic over multiple fields for performing inspection, delivery and surveillance applications among other operations. However, achieving the utmost efficiency requires drones to perform these tasks without the need of human intervention, which demands a robust and accurate localization system for achieving a safe and efficient autonomous navigation. Nevertheless, currently used satellite-based localization systems like GPS are insufficient for high-precision applications, especially in harsh scenarios like indoor and deep urban environments. In these contexts, Local Positioning Systems (LPS) have been widely proposed for satisfying the localization requirements of these vehicles. However, the performance of LPS is highly dependent on the actual localization architecture and the spatial disposition of the deployed sensor distribution. Therefore, before the deployment of an extensive localization network, an analysis regarding localization architecture and sensor distribution should be taken into consideration for the task at hand. Nonetheless, no actual study is proposed either for comparing localization architectures or for attaining a solution for the Node Location Problem (NLP), a problem of NP-Hard complexity. Therefore, in this paper, we propose a comparison among synchronous LPS for determining the most suited system for localizing UAVs over urban scenarios. We employ the Cràmer–Rao-Bound (CRB) for evaluating the performance of each localization system, based on the provided error characterization of each synchronous architecture. Furthermore, in order to attain the optimal sensor distribution for each architecture, a Black-Widow-Optimization (BWO) algorithm is devised for the NLP and the application at hand. The results obtained denote the effectiveness of the devised technique and recommend the implementation of Time Difference Of Arrival (TDOA) over Time of Arrival (TOA) systems, attaining up to 47% less localization uncertainty due to the unnecessary synchronization of the target clock with the architecture sensors in the TDOA architecture.S
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