• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 30
  • 10
  • Tagged with
  • 40
  • 40
  • 40
  • 40
  • 40
  • 40
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 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.
11

DEVELOPMENT OF AN EMI MEASUREMENT SYSTEM : Performance Analysis of Bluetooth communication under noise environment

Perez, Felix, Ferrer, Javier January 2008 (has links)
This thesis is a project carried out at the “Centre for RF Measurements Technology of Gävle”. The first aim of this work was basically to develop an EMI measurement system, to that purpose, it has been used an EMI Tester receiver, Spectrum Analyzer and a broadband antenna. Tables and graphics are shown to provide the values of the different detectors utilized. Using this measurement system, an interference file was recorded and then inserted in a Bluetooth communication model. The interference file was simulated with Matlab Simulink, to check how the interference affected the communication; the effects of the signal degradation are presented in a graphic. Finally a real Bluetooth communication was established using two Bluetooth modules from Free2Move Company, to prove that the effect of microwave oven interferences produces the increase of transmission time and therefore decrease the Throughput.
12

The Plausibility of implementing Receive Antenna Diversity in the Downlink of CDMA450 system

Sayago Montilla, David January 2010 (has links)
No description available.
13

Tjockleksmätning med ultraljud : Icke konventionell metod med signalbehandling

Östlin, Anders January 2010 (has links)
Tjockleksmätning av rör med ultraljud görs typiskt genom att mäta tiden mellan två efterföljande ekon av en utsänd puls. Detta är ofta en svår process som är känslig för störningar och påverkan utifrån. Denna rapport beskriver hur detta i stället kan göras i frekvensdomänen för att minska effekterna av dessa problem. För att göra detta härleds en signalmodell som beskriver de effekter som är nödvändiga för att utföra mätningarna. Utifrån signalmodellen togs metoder fram för att analysera och fastställa tjockleken på den uppmätta signalen. En av metoderna fungerar så bra att den skulle kunna användas. / Ultrasonic thickness gauging of steel tubes is typically performed by observing the time difference between two following echoes. This process is often connected to various problems regarding interference. This thesis describes how to avoid these problems by using signal processing and analyzing the signals in the frequency domain. To achieve these results a signal model that describes the necessary effects is derived. From this model different measurement methods to analyze and determine the thickness are developed. One of the methods proved to be useful.
14

Precision Amplifier for Applications in Electrical Metrology / Precisionsförstärkare för tillämpning inom elektrisk metrologi

Johanssson, Stefan January 2009 (has links)
<p>This master's thesis addresses two main problems. The first is how to suppress a common mode voltage that appears for current shunts, and the second how to let a voltage divider work under an unloaded condition to prevent loading errors and thereby a decreased measurement accuracy. Both these problems occurs during calibration of power meters, and verification of current shunts and voltage dividers. To the first problem three alternative solutions are presented; prototype a proposed instrumentation amplifier circuit, evaluate the commercial available instrumentation amplifier Analog Devices AD8130 or let the voltage measuring device suppress the common mode voltage. It is up to the researchers at SP to choose a solution. To address the second problem, a prototype buffer amplifier is built and verified. Measurements of the buffer amplifier show that it performs very well. At 100 kHz, the amplitude error is less than 20 μV/V, the phase error is less than 20 μrad, and the input R<sub>p</sub> is over 10 MΩ. This is performance in line with the required to make accurate measurements possible at 100 kHz and over that.</p>
15

Investigation of alternative current measurements in high-voltage applications

Holmgren, Jens January 2007 (has links)
<p>ABB:s MACH2 system uses a number of currents to ignite thyristors for AC/DC-trassfformation and they are measured for control and protection. The measurement methods used today has major drawbacks. Two alternative techniques are investigated, one based on the Hall-Effect (HED) and the other based on Anisotropic Magnetoreistanse (AMR), both techniques sensing the magnetic field produced by currents in a conductor. The HED hawe low sensitivity so some kind of flux concentrators is needed. This adds volume, costs and complexity to the device. The AMR technique is much more sensitive than the HED. Unfortunately AMR are also much more sensitive for high over currents that may damage the devise, and they are not as common on te market. By testing linearity, step response and frequency dependency for some components, my conclusion is that HED components with toroidal flux concentrators utilizing magnetic feedback (Closed Loop, CL) may be used in this particular application. A drawback with CL are that they, when measuring sharp edged step signals, suffer from overshoots at the output that might activate the over current protection.</p>
16

GPS/Optical Encoder Based Navigation Methods for dsPIC Microcontroled Mobile Vehicle

Dincay, Berkan January 2010 (has links)
<p>Optical encoders are being widely suggested for precise mobile navigation. Combining such sensor information with Global Positioning System (GPS) is a practical solution for reducing the accumulated errors from encoders and moving the navigational base into global coordinates with high accuracy.</p><p>This thesis presents integration methods of GPS and optical encoders for a mobile vehicle that is controlled by microcontroller. The system analyzed includes a commercial GPS receiver, dsPIC microcontroller and mobile vehicle with optical encoders. Extended kalman filtering (EKF), real time curve matching, GPS filtering methods are compared and contrasted which are used for integrating sensors data. Moreover, computer interface, encoder interface and motor control module of dsPIC microprocessor have been used and explained.</p><p>Navigation quality on low speeds highly depends greatly upon the processing of GPS data. Integration of sensor data is simulated for both EKF and real time curve matching technique and different behaviors are observed. Both methods have significantly improved the accuracy of the navigation. However, EKF has more advantages on solving the localization problem where it is also dealing with the uncertainties of the systems.</p>
17

Model-based pre-distortion for Signal Generators

Luque, Carolina January 2007 (has links)
<p>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.</p><p>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.</p><p>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.</p>
18

Investigation of Antennas for C2C communication

Waqas, Abdul January 2010 (has links)
<p>The road traffic density is continuously increasing. By the intensive use of automobiles, it comes</p><p>to considerable difficulties and unpredictable events. The frequency of traffic obstructions, traffic</p><p>jams and accidents will also increase in future. A solution for this problem would be that</p><p>the driver would be supplied information when he is on the road. The information should be</p><p>including about road and traffic conditions and also information about other vehicles, which in</p><p>the near vicinity.</p><p>This kind of information sharing between vehicles is called C2C communication.Especially in</p><p>Europe there are many projects which are working for different C2C communcation applications,</p><p>like.</p><p>Objective of this thesis is based on former works, which optimized the antenna positions</p><p>for C2C communication by ray tracing simulation. The investigation of antennas for the C2C</p><p>communication, two different approches are taken in to account, a narrow band, and broad band.</p><p>Investigation of transparent material for broad band is also the part of this thesis.</p>
19

PLC-Baserat Maskinlarm ombord Ms Calmare Nyckel

Andersson, Robert, Huss, Karl, Lagerberg, Henrik January 2009 (has links)
<p> </p><p>Denna examensrapport beskriver arbetet med att utveckla ett nytt övervaknings och maskinalarmsystem till utbildningsfartyget M/S Calmare Nyckel. Systemet som konstruerades är styrdatorbaserat med grafiskt presentation av driftsvärden.</p><p>Projektet drevs av tre sjöingenjörsstudenter på Sjöfartshögskolan i Kalmar.</p><p> </p> / <p>This graduate report describes the work relating to the development of a brand new monitoring and machinery alarm system onboard the training vessel M/S Calmare Nyckel. The system developed, is based on PLC automation technology, and allows graphical presentation of system data.</p><p>The project was managed by three marine engineering students at the Kalmar Maritime Academy.</p> / Klassning av alarmsystemet genomfördes 2009-05-18 av inspektör från transportstyrelsen. Systemet godkändes.
20

Nyinstallation av Larmsystem Till NOHAB-Diesel : Denna rapport innefattar förfarande från att konstruera och installera ett helt nytt larmsystem

Olsen, Erik, Larsson, Jens, Stjernström, Dennis January 2009 (has links)
<p>Skolfartyget M/S Calmare Nyckel, som ägs och opereras av Sjöfartshögskolan i Kalmar används i utbildningssyfte av både blivande nautiker och maskinbefäl.</p><p> </p><p>Driften av NOHAB-dieseln, som används som generator, har varit problemfylld med ständiga och oförklarliga stopp. Det larmsystem som installerades av Oskarshamnsvarvet var högst bristfälligt. Larmsystemet var personfarligt då det var byggd på 230volt, dessutom var larmpunkterna byggda i serie med endast en stoppindikering. Avsaknaden av elritningar över systemet gjorde att bristerna i larmsystemet inte kunde felsökas.<strong> </strong>Dessutom fanns ingen indikering i kontrollrummet utan endast lokalt vid NOHAB-dieseln.</p><p> </p><p>Vi har gjort en nyinstallation av larmsystemet på mer personsäkra 24VDC, med samtliga larmpunkter parallella och med tillhörande indikering på panel, både lokalt vid NOHAB-dieseln samt i pulpeten för god översyn av systemet. Vidare har vi gjort kompletta ritningar över systemet för en god överblick och möjlighet att felsöka.</p><p>I rapporten beskriver vi tillvägagångssättet för problemlösningar som uppstått under arbetet med att skapa ett fungerande larmsystem.</p> / <p><em> </em>School ship M/S Calmare Nyckel, owned and operated by the Maritime University of Kalmar is used for training by both prospective merchant marine officer as well as engineers. The operation of NOHAB-diesel, used as a generator, has been problematic with frequent and unexplained stop. The alarm system installed by the Oskarshamn Shipyard was highly dysfunctional. The alarm system was dangerous to personnel when it was built on 230volt, furthermore were the alarm points constructed in series with only a stop indication. The lack of electrical drawings of the system made it impossible to trouble shot the deficiencies in the alarm system. Moreover, there was no alarm indication in the control room but only locally at the NOHAB-diesel.</p><p> </p><p>We have made a new installation of the alarm system with the higher personal safety 24VDC, with all the alarms parallel with the corresponding indication on the panel, both locally at the NOHAB-diesel and on the control table for good review of the system. Furthermore, we have made complete drawings of the system enabling a good overview and the ability to troubleshoot.In this report we describe the approach to the problem solutions that have emerged in the process of creating a functioning alarm system.</p>

Page generated in 0.0877 seconds