NSMS probe recorder design and development

The real-time Non-Contact Stress Measurement System (NSMS) currently used at AEDC calculates the vibration of rotating blades by capturing the time of arrival for each blade. The time of arrival is determined by a triggering circuit that is activated when the signal from the engine probe crosses a predetermined threshold. In its current configuration, the NSMS system only saves post-processed data. A system that records the raw signals from the probes was developed to allow reprocessing the data whenever necessary. The probe recorder system consists of analog-to-digital conversion hardware to capture the signals, data storage for the files, and digital-to-analog hardware to replay the signals. The system accommodates a maximum of 32 channels, a maximum sampling rate of 20 MHz, and a total bandwidth of up to 160 megabytes per second. Sixteen-bit resolution is used in digitizing the analog waveforms to minimize quantization errors.The incoming data is transferred using FPDP, capable of 160 MB/sec, and PCI-X, capable of 528 MB/sec. Large amounts of high speed (3200 MB/sec) random access memory coupled with two dual-core processors were included for data transfer buffering and program execution. As the final destination, a RAID array connected to a PCI Express interface was implemented for 240 MB/sec data storage. Laboratory tests were conducted on the system to verify performance. The RAID array exceeded expectations for disk writing but reduced bandwidth was observed for read operations. The relationship between the input analog signals and the reproduced waveforms was checked and, except for one case, performed identically to the simulated system transfer function. Long duration tests were performed to verify data transfers at the maximum settings and proved that the system could operate continuously without data loss.Due to the large amounts of data, a brief study of offline compression techniques was conducted. Lossy compression was investigated but was not implemented at this time due to unwanted distortion and loss of critical data. Lossless compression using WinZip was implemented as a compromise between ideal compression ratios and data retention expectations

Impedance-Oriented Transient Instability Modeling of SiC MOSFET Intruded by Measurement Probes

Due to the breakneck switching speed, SiC mosfet is extremely sensitive to parasitics in the power device, circuit layout, and also measurement probe. It is not clear how the parasitics of measurement probes affect the transient stability of SiC mosfet, and it poses an unsolved challenge for the industrial field. This paper focuses to uncover the transient instability mechanism of SiC mosfet intruded by probes. Mathematical and circuit models of voltage and current probes are created, by considering the parasitics, input impedance, and bandwidth issues. To reveal the stability principles of SiC mosfet associated with probes, impedance-oriented and heterogeneity-synthesized models combining device with probes are proposed. Furthermore, an assessment methodology and root locus analysis are presented to demonstrate the transient stability schemes and the stable boundaries of SiC mosfet influenced by multiple factors, including probe parasitics, device parameters, gate resistances, and snubber circuits. Comparative experiments are presented to confirm the transient behaviors of SiC mosfet intruded by probe parasitics and regulated by control circuits. It is proven that, because of low bandwidth specifications, the large input capacitance of the voltage probe and coil inductance of the current probe degrade the transient stability of SiC mosfet. Due to the deteriorated stability margin of SiC mosfet intruded by the inserted parasitics of probes, instability may also be activated by using the small gate resistance. The snubber circuit is helpful to enhance the transient stability. Advanced probes with high bandwidth and high impedance are crucially needed for stable measurement of wide bandgap power devices like SiC mosfet.Ministry of Education (MOE)Nanyang Technological UniversityThis work was supported in part by the National Natural Science Foundation of China under Grant 51607016, in part by the National Key Research and Development Program of China under Grant 2017YFB0102303, in part by Singapore ACRF Tier 1 Grant RG 85/18, and in part by the NTU Startup Grant (SCOPES) for Prof Zhang Xin

Sensor prototype for checkerboard visual evoked potentials

Trabajo de InvestigaciónIn this project the development of a sampling system of encephalographic signals stimulated by visual evoked potentials is disclosed. Through the design and construction of an analog sensor, the reading, amplification and filtering of encephalographic signals captured by dry electrodes is proposed. These signals are processed and taken to digital values to be sampled and analyzed by statistical techniques that allow the signal variations to be recognized and standardized against stimuli of visual evoked potentials presented at different frequencies. This system is proposed as a support system for the interpretation of data that may indicate neurodegenerative diseases with which psychologists and psychiatrists can work and diagnose patients.1. INTRODUCTION 2. PROBLEM STATEMENT 3. OBJECTIVES 4. CONCEPTUAL FRAMEWORK ¡Error! Marcador no definido. 5. THEORETICAL FRAMEWORK ¡Error! Marcador no definido. 6. STATE OF THE ART 7. METHODOLOGY 8. NOVEL CHARACTER OF THE PROJECT 9. ANALOG CIRCUIT DESIGN AND SIMULATION 10. ANALOG CIRCUIT ASSEMBLY 11. RESULTS 12. VALIDATION OF PROJECT 13. CONCLUSIONS AND FUTURE WORKS 14. ANNEXES 15. REFERENCIASMaestríaMagister en Ingeniería y Gestión de la Innovació

Spatially Distributed Interferometric Receiver for 5G Wireless Communications and Sensing Applications

RÉSUMÉ Les systèmes de télécommunications sans fils ont connu une révolution et un succès sans précédent dans l’histoire humaine, et ce depuis l’introduction de la première génération des réseaux mobiles au début des années 1980. Alors que ce premier standard de communication était essentiellement basé sur des méthodes de modulation analogique du signal, ce qui ne permettait que la transmission de la voix, les générations des systèmes de télécommunications qui ont succédé depuis le deuxième standard mondial GSM, se sont basées sur la transmission numérique qui représente une plateforme universelle pour le traitement des données de toute sorte (voix, donnés texte, vidéos haute définition, etc, ). En effet, le traitement numérique du signal qui a débuté avec les premiers travaux sur la théorie de l’information, aux laboratoires Bell aux États-Unis vers la fin des années quarante du siècle passé, constitue le noyau dur de tous les standards de communication, y-compris la cinquième génération des réseaux 5G, dont la date d’entrée au marché mondial est prévue vers le début de l’année prochaine 2020. En effet, les réseaux de communications sans fils actuels, avec au sommet de la pyramide le standard 4G-LTE, ne peuvent pas répondre aux attentes des utilisateurs et des entreprises en termes de débit de transmission de données qui ne cesse d’augmenter d’une façon exponentielle, et pouvant atteindre les 40 Exabytes par mois vers 2020. De plus, la naissance du concept de l’internet des objets (IoT) qui consiste en l’interconnexion d’un très grand nombre de mini-capteurs sans fils qui vont gérer des milliers, voire des millions d’activités des toutes sortes, tels que l’aide à la conduite des voitures dans les routes, le contrôle des températures et des feux dans les régions forestières, la transmission des données médicales des patients en temps réel vers les centres hospitaliers, etc. Dans le but de répondre aux besoins actuels et futurs, la venue de la cinquième génération des réseaux des communications 5G est devenue urgente plus que jamais. En effet, ce nouveau standard ne sera pas une amélioration incrémentale de la 4G-LTE, mais sera plutôt toute une nouvelle plateforme intelligente offrant des débits de données allant jusqu'à plusieurs gigabits par seconde, avec un temps de latence ne dépassant pas 1 milliseconde dans le but d’assurer une qualité de service sans égal.----------ABSTRACT Wireless communication systems are one of the most famous success stories in the field of engineering in modern era. In fact, the birth of the first generation of mobile communications goes back to the early 1980’s. This first standard was based on analog modulation with the aim of transmitting only voice signals. And with the progress made in signal processing techniques and the large-scale productions of digital integrated circuits, the second generations of wireless communications was introduced in the nineties of the last century. Since then, a new standard for wireless mobile systems has been introduced every ten years or so, with ever increasing data rates, lower latency and better quality of service, thanks to the adoption of sophisticated modulation schemes and robust error correcting codes, in conjunction with improved hardware capabilities over the years. The magic progress in wireless technologies is strongly related to the magnificent research work pioneered by Claude Shannon on information theory in 1948 at Bell-labs, in combination with continuous research efforts conducted by millions of brilliant minds worldwide. However, the current wireless generation of wireless systems 4G-LTE is unable to follow the explosion of wireless traffic, which is trigged by the exponential demand for higher data rates, which would create monthly traffic of about 40 Exabytes by 2020. Moreover, the birth of Internet of Things (IoT) concept is a driving force towards the emergence of a huge platform of billions of interconnected devices and sensors, used to control and monitor an ever-increasing number of applications (forests fire detection, intelligent cars, real-time health monitoring for sick and old people , etc.). As a matter of fact, the upcoming of the fifth generation (5G) of wireless mobile networks has become a very urgent necessity in order to meet the widely-discussed system requirements in terms of capacity, latency and quality of service. Consequently, elements of the physical layer must be redrawn and reorganized in order to avoid the prohibited cost of network deployment and power consumption of billions of interconnected devices

LED-to-LED communication: a bidirectional low-complexity system based on RGB LEDS as receiver

This thesis studies, designs and characterises a low-complexity bidirectional LED-to-LED communication system employing only off-the-shelf tricolour light emitting diodes (LEDs) as transmitters and receivers with the aim of providing the required connectivity for contemporary small Internet-of-things (IoT) devices. In today’s interconnected world of Internet of Things devices, it is imperative to have low-complexity and small size communication modules to enable seamless communication between such small devices over short distances and with low data rates without exhausting the already over-crowded radio frequency spectrum. While a regular visible light communication (VLC) system containing an LED and a photodiode is a viable option, it provides only one-directional communication. To enable an uplink, a repetition of the downlink is usually provided, doubling the cost, complexity and space of the original circuits. Hence, an LED-to-LED solution maximises the benefit of VLC and imitates the idea of having one antenna for transmitting and receiving, known in radio frequency (RF) technologies. In order to design an LED-to-LED system, the LED is characterised as transmitter and receiver both qualitatively and empirically. The results confirmed the feasibility of the LED as a wavelength-selective and directional photodetector with a field of view of 18° and low responsivity of 0.2 mA/W under zero bias. Interestingly, the experiments also reveal that the LED could even detect light when slightly forward biased. Based on the identified characteristics of the LED, a current-mirror-based LED driver, a transimpedance amplifier and an analogue switch are designed and separately evaluated to mitigate the low responsivity of the LED as photodetector. The VLC channel is also characterised and the interference due to the most common contemporary ambient light sources is evaluated. The interference of each light source is mathematically modelled based on the empirical results. The overall LED-to-LED link is practically implemented and optimised to reach data rates up to 200 kbps at distances up to 7 cm with the help of an optimised matched filter at the detection phase. The analogue switch completes the system by providing the option of a bidirectional half-duplex channel while avoiding flickering. At a switching frequency of up to 300 Hz, the LED-to-LED system could deliver error-free data transmission at speeds up to 100 kbps in a back-to-back configuration. The findings of this thesis indicate that a bidirectional low-complexity VLC system depending only on RGB LED for transmission and photodetection is not only feasible, but also a very viable option for short-range, low-speed communication between small IoT devices with high potential of commercial deployment