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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Model-based pre-distortion for Signal Generators

Luque, Carolina January 2007 (has links)
Spectrally pure signals are an indispensable requirement when the Signal Generator (SG) is to be used as part of a test bed. However, even sophisticated equipment may not comply with the needs imposed by certain applications. This work approaches the problem by using Digital Pre-Distortion (DPD) based on a polynomial memory-less model obtained for the SG. Using the SG in arbitrary mode (ARB) an input signal is computer-generated and reproduced by the SG. Measurement accuracy is ensured using coherence sampling and grid matching to the Signal Analyzer (SA). Finally, careful time alignment is used to compare the transmitted and received three-tone signals to obtain the polynomials coefficients. Results show that the accuracy of the model and the effectiveness of pre-distortion may vary depending on the amplitude of the three-tone signal. However, using polynomials of 5th and 9th degrees up to 15dB reduction of the 3rd order Inter-Modulation products can be obtained, and spurious powers may be lowered down to 70dBc.
32

Robot Positioning System : Underwater Ultrasonic Measurement

Salido Monzú, David, Roldán Sánchez, Oliver January 2009 (has links)
<p>This document provides a description about how the problem of the detection of thecenter of a defined geometry object was solved.This named object has been placed in an experimental environment surrounded bywater to be explored using microwaves under the water, to try to find a possibletumor. The receiver antenna is fixed in the tip of the tool of an ABB robot.Due to this working method, it was necessary to locate the center of this object tomake correctly the microwave scanning turning always around the actual center. Thiswork not only consist in give a hypothetic solution to the people who gave us theresponsibility of solve their problem, it is also to actually develop a system whichcarries out the function explained before.For the task of measuring the distance between the tip of the tool where themicrowave antenna is, ultrasonic sensors has been used, as a complement of acomplete system of communication between the sensor and finally the robot handler,using Matlab as the main controller of the whole system.One of these sensors will work out of water, measuring the zone of the object which isout of the water. In the other hand, as the researching side of the thesis, a completeultrasonic sensor will be developed to work under water, and the results obtained willbe shown as the conclusion of our investigation.The document provides a description about how the hardware and software necessaryto implement the system mentioned and some equipment more which were essentialto the final implementation was developed step by step.</p>
33

Åtgärder för att minimera kommunikationsstörningar vid avläsning av elmätare via elnätet / Measures for minimising communication disturbances when reading electricity meters via the power grid

Därnemyr, Johan January 2009 (has links)
<p>Detta examensarbete tar upp frågan om kommunikationsproblem mellan de komponenter som ingår i ADDAX systemet, till största del de problem som uppstår mellan router och mätare. ADDAX systemet är uppbyggt på ett hierarkiskt vis med ADDAX server högst upp och mätaren längs ned. Systemet kommunicerar via PLC ”power line comunication”. Uppgiften har varit att kartlägga hur mätsystemet fungerar, vilka geografiska problemområden som finns med avseende på kommunikations problem, lokalisering av störkällor, åtgärdning av dessa störkällor och framtagande av ett flödesschema som skall kunna användas av montörerna vid felsökning i systemet. Arbetet inleddes med att ta fram underlag för vilka områden som påverkas av störningar i elnätskommunikationen. Detta gjordes med hjälp av programmet ”TC Meter Surv SA Edition 0.61” som arbetar mot ADDAX systemets databas för att se vilka mätare som är installerade och vilka som kommunicerar med systemet. Efter vissa problem togs två områden fram, ett på landsbygden och ett i centrala Grästorp. Vid mätning i dessa områden användes till en början två instrument, PL-monitor och HF+. HF+ visade sig vara överflödigt då samma information ges av PL-monnitor båda versioner visar på vilka störningsnivåer som finns i elnätet. HF+ är mer svårtolkat då användaren själv måste ta ställning till informationen som visas medan PL-monnitor enbart visar på den störning som stör ut kommunikationen. Då mätningarna genomförts och analyserats har det visat sig att programmet ej fungerat tillfredställande och att fel information om antal felaktiga mätare i de område som är beläget i centrala Grästorp, detta har resulterat i att en ny slutsats dragits där istället för en störning i LV nu problemet verkar ligga i MV. Kommunikations problemet på landsbygden kan troligtvis lösas med att installera filter hos de kunder vars mätare ej kommunicerar. Andra åtgärder som kan vara aktuella vid framtida kommunikationsproblem kan vara byta av kommunikations fas på mätaren, flytt av mätaren till matningsskåp, installation av repeterare eller att i samråd med kund få denna att stänga av störande utrustning vissa tider på dygnet. En slutsats som dragits av de erfarenheter som ackumulerats under projektets gång är att all mjukvara bör uppdateras och att master-routrar ersätts med en nyare version.</p> / <p>This report handles the issue of communication problems that appears between the components in the ADDAX system, mainly between the router and meter. The system is built around a hierarchy with the ADDAX server at the top and the meter at the bottom. The system uses the power grid as communication medium, this is called PLC “power line communication. The task has bin to se how the system works, witch geographical areas that have problems with communication, localization of source for the disturbing of the communication, attend to the disturbing and to make a flow chart that the electricians can use when they are conducting a measurement. A program called “TC Meter Surv SA Edition 0.61” was used for finding which areas that have problems with the communication. Two areas were chosen, one in the countryside and one in central Grästorp. The program firs showed that some meters where missing but when the measurements where don the program showed that all meters where missing. The reason for this problem is unknown. The problem in the central Grästorp area is not in the LV butt in the MV. The conclusion will be that al of the software must be updated and that the master routers could be replaced with a never versions before any new measurements are to be done. The power quality measurement instruments that has bin used are PL-monitor and HF+. On other conclusion that can bi don is that HF+ is superfluous because it chows the same information that PL-monitor dose but it’s harder to interpret. In the area on the countryside the solution to the communication problem can bi to install a filter. Other solutions to PLC problems can bi to switch the phase the meter uses for communication, move the meter farther from the customer, installing a repeater or in consultation with the customer get him or here to turn of the devise that disturb the communication under some ours in a 24-hour period.</p>
34

Integrated Optical Slot-Waveguide Ring Resonator Sensor Arrays for Lab-on-Chip Applications

Gylfason, Kristinn Björgvin January 2010 (has links)
This thesis treats the development of an integrated optical sensor array. The sensors are slot-waveguide ring resonators, integrated with on-chip surface grating couplers and light splitters, for alignment tolerant, real-time, refractive index sensing, and label-free biosensing. The work includes: the design of components and system layouts, the development of fabrication methods, the fabrication of sensor chips, the characterization of the chips, and the development of physical system models for accurate extraction of resonance wavelengths in measured spectra. The main scientific achievements include: The evaluation of a novel type of nano-structured optical waveguide for biochemical sensing. The realization of an array of such slot-waveguide sensors, integrated with microfluidic sample handling, for multiplex assays. The first study of the thermal behavior of slot-waveguide sensors and the discovery of unique temperature compensation capabilities. From an application perspective, the use of alignment tolerant surface gratings to couple light into the optical chip enables quick replacement of cartridges in the read-out instrument. Furthermore, the fabrication sequence avoids polishing of individual chips, and thus ensures that the cost benefits of silicon batch micro-fabrication can be leveraged in mass production. The high sensitivity of the slot waveguide resonators, combined with on-chip referencing and physical modeling, yields low limits of detection. The obtained volume refractive index detection limit of 5 × 10−6 refractive index units (RIU), and the surface mass density detection limit of 0.9 pg/mm2, shows that performance comparable to that of commercial non-integrated surface plasmon resonance sensors, made from bulk optical components, canbe achieved in a compact cartridge. / Qc20100715 / SABIO
35

Robot Positioning System : Underwater Ultrasonic Measurement

Salido Monzú, David, Roldán Sánchez, Oliver January 2009 (has links)
This document provides a description about how the problem of the detection of thecenter of a defined geometry object was solved.This named object has been placed in an experimental environment surrounded bywater to be explored using microwaves under the water, to try to find a possibletumor. The receiver antenna is fixed in the tip of the tool of an ABB robot.Due to this working method, it was necessary to locate the center of this object tomake correctly the microwave scanning turning always around the actual center. Thiswork not only consist in give a hypothetic solution to the people who gave us theresponsibility of solve their problem, it is also to actually develop a system whichcarries out the function explained before.For the task of measuring the distance between the tip of the tool where themicrowave antenna is, ultrasonic sensors has been used, as a complement of acomplete system of communication between the sensor and finally the robot handler,using Matlab as the main controller of the whole system.One of these sensors will work out of water, measuring the zone of the object which isout of the water. In the other hand, as the researching side of the thesis, a completeultrasonic sensor will be developed to work under water, and the results obtained willbe shown as the conclusion of our investigation.The document provides a description about how the hardware and software necessaryto implement the system mentioned and some equipment more which were essentialto the final implementation was developed step by step.
36

Åtgärder för att minimera kommunikationsstörningar vid avläsning av elmätare via elnätet / Measures for minimising communication disturbances when reading electricity meters via the power grid

Därnemyr, Johan January 2009 (has links)
Detta examensarbete tar upp frågan om kommunikationsproblem mellan de komponenter som ingår i ADDAX systemet, till största del de problem som uppstår mellan router och mätare. ADDAX systemet är uppbyggt på ett hierarkiskt vis med ADDAX server högst upp och mätaren längs ned. Systemet kommunicerar via PLC ”power line comunication”. Uppgiften har varit att kartlägga hur mätsystemet fungerar, vilka geografiska problemområden som finns med avseende på kommunikations problem, lokalisering av störkällor, åtgärdning av dessa störkällor och framtagande av ett flödesschema som skall kunna användas av montörerna vid felsökning i systemet. Arbetet inleddes med att ta fram underlag för vilka områden som påverkas av störningar i elnätskommunikationen. Detta gjordes med hjälp av programmet ”TC Meter Surv SA Edition 0.61” som arbetar mot ADDAX systemets databas för att se vilka mätare som är installerade och vilka som kommunicerar med systemet. Efter vissa problem togs två områden fram, ett på landsbygden och ett i centrala Grästorp. Vid mätning i dessa områden användes till en början två instrument, PL-monitor och HF+. HF+ visade sig vara överflödigt då samma information ges av PL-monnitor båda versioner visar på vilka störningsnivåer som finns i elnätet. HF+ är mer svårtolkat då användaren själv måste ta ställning till informationen som visas medan PL-monnitor enbart visar på den störning som stör ut kommunikationen. Då mätningarna genomförts och analyserats har det visat sig att programmet ej fungerat tillfredställande och att fel information om antal felaktiga mätare i de område som är beläget i centrala Grästorp, detta har resulterat i att en ny slutsats dragits där istället för en störning i LV nu problemet verkar ligga i MV. Kommunikations problemet på landsbygden kan troligtvis lösas med att installera filter hos de kunder vars mätare ej kommunicerar. Andra åtgärder som kan vara aktuella vid framtida kommunikationsproblem kan vara byta av kommunikations fas på mätaren, flytt av mätaren till matningsskåp, installation av repeterare eller att i samråd med kund få denna att stänga av störande utrustning vissa tider på dygnet. En slutsats som dragits av de erfarenheter som ackumulerats under projektets gång är att all mjukvara bör uppdateras och att master-routrar ersätts med en nyare version. / This report handles the issue of communication problems that appears between the components in the ADDAX system, mainly between the router and meter. The system is built around a hierarchy with the ADDAX server at the top and the meter at the bottom. The system uses the power grid as communication medium, this is called PLC “power line communication. The task has bin to se how the system works, witch geographical areas that have problems with communication, localization of source for the disturbing of the communication, attend to the disturbing and to make a flow chart that the electricians can use when they are conducting a measurement. A program called “TC Meter Surv SA Edition 0.61” was used for finding which areas that have problems with the communication. Two areas were chosen, one in the countryside and one in central Grästorp. The program firs showed that some meters where missing but when the measurements where don the program showed that all meters where missing. The reason for this problem is unknown. The problem in the central Grästorp area is not in the LV butt in the MV. The conclusion will be that al of the software must be updated and that the master routers could be replaced with a never versions before any new measurements are to be done. The power quality measurement instruments that has bin used are PL-monitor and HF+. On other conclusion that can bi don is that HF+ is superfluous because it chows the same information that PL-monitor dose but it’s harder to interpret. In the area on the countryside the solution to the communication problem can bi to install a filter. Other solutions to PLC problems can bi to switch the phase the meter uses for communication, move the meter farther from the customer, installing a repeater or in consultation with the customer get him or here to turn of the devise that disturb the communication under some ours in a 24-hour period.
37

Electrical and Optical Charactristics of InP Nanowire Photodetectors

MALEKRAH, MEHDI January 2010 (has links)
<p>In this project Fourier Transform Infrared Spectroscopy is used to investigate a new kind of photodiode that is based on nanowires. The photo current and I-V curves for different temperatures, different applied biases, in darkness and illumination condition have been studied. The experiment was conducted in the temperature range from 78 K (-195ºC) to 300 K (27ºC). These photo diodes are designed to work on NIR wavelengths. The results show some excellent properties, such as high break down voltage, and that is an important advantage for photo detectors, low and constant reverse saturation current (Is). The results show some defects, most of them come from fabrication. The design of the sample is also discussed.</p>
38

Ultrasonic Arrays for Sensing and Beamforming of Lamb Waves

Engholm, Marcus January 2010 (has links)
Non-destructive testing (NDT) techniques are critical to ensure integrity and safety of engineered structures. Structural health monitoring (SHM) is considered as the next step in the field enabling continuous monitoring of structures. The first part of the thesis concerns NDT and SHM using guided waves in plates, or Lamb waves, to perform imaging of plate structures. The imaging is performed using a fixed active array setup covering a larger area of a plate. Current methods are based on conventional beamforming techniques that do not efficiently exploit the available data from the small arrays used for the purpose. In this thesis an adaptive signal processing approach based on the minimum variance distortionless response (MVDR) method is proposed to mitigate issues related to guided waves, such as dispersion and the presence of multiple propagating modes. Other benefits of the method include a significant increase in resolution. Simulation and experimental results show that the method outperforms current standard processing techniques. The second part of the thesis addresses transducer design issues for resonant ultrasound inspections. Resonant ultrasound methods utilize the shape and frequency of the object's natural modes of vibration to detect anomalies. The method considered in the thesis uses transducers that are acoustically coupled to the inspected structures. Changes in the transducer's electrical impedance are used to detect defects. The sensitivity that can be expected from such a setup is shown to highly depend on the transducer resonance frequency, as well as the working frequency of the instrument. Through simulations and a theoretical argumentation, optimal conditions to achieve high sensitivity are given.
39

Electrical and Optical Charactristics of InP Nanowire Photodetectors

MALEKRAH, MEHDI January 2010 (has links)
In this project Fourier Transform Infrared Spectroscopy is used to investigate a new kind of photodiode that is based on nanowires. The photo current and I-V curves for different temperatures, different applied biases, in darkness and illumination condition have been studied. The experiment was conducted in the temperature range from 78 K (-195ºC) to 300 K (27ºC). These photo diodes are designed to work on NIR wavelengths. The results show some excellent properties, such as high break down voltage, and that is an important advantage for photo detectors, low and constant reverse saturation current (Is). The results show some defects, most of them come from fabrication. The design of the sample is also discussed.
40

Antenna elements matching : time-domain analysis

Condori-Arapa, Cristina January 2010 (has links)
Time domain analysis in vector network analyzers (VNAs) is a method to represent the frequency response, stated by the S-parameters, in time domain with apparent high resolution. Among other utilities time domain option from Agilent allows to measure microwave devices into a specific frequency range and down till DC as well with the two time domain mode: band-pass and low-pass mode. A special feature named gating is of important as it allows representing a portion of the time domain representation in frequency domain.   This thesis studies the time domain option 010 from Agilent; its uncertainties and sensitivity. The task is to find the best method to measure the antenna element matching taking care to reduce the influence of measurement errors on the results.   The Agilent 8753ES is the instrument used in the thesis. A specific matching problem in the antenna electric down-tilt (AEDT) previously designed by Powerwave Technologies is the task to be solved. This is because it can not be measured directly with 2-port VNAs. It requires adapters, extra coaxial cables and N-connectors, all of which influences the accuracy. The AEDT connects to the array antenna through cable-board-connectors (CBCs). The AEDT and the CBCs were designed before being put into the antenna-system. Their S-parameters do not coincide with the ones measured after these devices were put in the antenna block.   Time domain gating and de-embedding algorithms are two methods proposed in this thesis to measure the S-parameters of the desired antenna element while reducing the influence of measurement errors due to cables CBCs and other connectors. The aim is to find a method which causes less error and gives high confidence measurements.   For the time domain analysis, reverse engineering of the time domain option used in the Agilent VNA 8753ES is implemented in a PC for full control of the process. The results using time-domain are not sufficiently reliable to be used due to the multiple approximations done in the design. The methodology that Agilent uses to compensate the gating effects is not reliable when the gate is not centered on the analyzed response. Big errors are considered due to truncation and masking effects in the frequency response.   The de-embedding method using LRL is implemented in the AEDT measurements, taking away the influences of the CBCs, coaxial cables and N-connector. It is found to have sufficient performance, comparable to the mathematical model. Error analysis of both methods has been done to explaine the different in measurements and design.

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