<p>In this thesis, a measurement set-up has been developed to characterize high frequency medical ultrasound transducers using a pulse echo set-up. This work is a continuation of an earlier project. The aim of this project is to improve the instrumentation to get more reliable, repeatable and consistent results. The transducer used in this project was a 20MHz annular array transducer with 8 elements. Parameters such as the electroacoustic transfer function and reflection coefficients of element 1 and 2 have been found for a sinusoidal burst excitation and a Gaussian excitation, to give examples for the estimation of these parameters. Developing the right instrumentation for the pulse echo set-up and transducer for pulse echo measurements has been emphasised, where a transducer holder and reflector have been constructed for characterization of elements 1-5. A cylindrical water resistant reflector with a curved top was designed giving certain degrees of freedom as opposed to the pure spherical reflector concerning positioning of the reflector with respect to the transducer. A slanted bottom was included in the design of the reflector causing reflections from the bottom to diffract and thus stopping these from interfering with the reflections of interest happening at the top of the reflector surface. A transducer holder was also designed and custom made for the transducer used in the project, where both mechanical and electrical considerations have been taken, as the holder makes alignment of the transducer with respect to the reflector easier and coaxial cables have been introduced to get more control over the signals going to and from the transducer array. Coaxial cables were chosen as these are easy to model, and have clear specifications in addition to having the property of shielding noise signals. Alignment of the transducer has been emphasised to make radiation into the focus of the reflector easier, although the design of the reflector also allows the reflector to be tilted in the allocation of its focus point. By taking detailed lateral scans of echoes received by the transducer using a robot, in addition to varying the distance between the transducer and the reflector with an increment of 0.2 mm, the reflection coefficients were found to be very sensitive to lateral positioning, and to some extent sensitive to axial positioning of the transducer with respect to the reflector. The elimination of propagation delay due to the signals travel in waterpath and electrical transmission and reception chain leading to the transducer ports has also been compensated for, as these delays will effect the complex values of the transfer function. The electrical propagation delay is eliminated by using a simulation program, and analysis of the time between two consecutive echoes is done in order to find the physical time delay in the water path the pulses travelled. The electro acoustic transfer function has also been found for element 1 and element 2, but with a much greater time delay than what was expected. An uncertainty budget of the obtained parameters has also been done to see the impact of laboratory equipment on the meaurements. Estimation schemes to obtain reflection coefficients and the electro acoustic transfer function have been developed, which are repeatable for further characterization for the whole transducer array. Existing MATLAB codes have been modified in simulations and some new codes have been written for analyzing measurement based estimation of transfer functions, reflection coefficients and effects of various filters on their characteristics. Different types of filters have been used on the recorded echo signals to eliminate noise from the estimated reflection coefficients. A better control of the parasitic inductances due to the non coaxial cables in the system should perhaps be evaluated, and for further characterization of the transducer, the mechanical admittance can also be found by using the estimated reflection coefficients and electro acoustic transfer function.</p>

<p>The thesis concerns the design and prototype construction of a UHF half-duplex radio system, intended for use on board a small student satellite. The assignment is a continuance of a project assignment done during the fall of 2006, concerning the outline and specification of a new student satellite project at NTNU. The report details performance-deciding parameters of satellite communication systems operating at UHF frequencies, and fundamental information theory. Theory and application of RF design is discussed, along with complications in electronic engineering due to space environment factors. The report goes on to describe the design process and prototype development of a UHF transceiver intended for use in small, low power LEO satellites.</p>

<p>In this assignment the theoretical background for the nature of speckle is presented and practical work was done to reduce the speckle effect in a display system based on a laser source. This was done without any picture modulators, or any kind of line scan or flying spot scanning. Work was done to find the right setup to be able to as easy as possible characterize the statistics of the speckle in an image. A still image of an expanded laser spot worked as an image. A series of test sets were carried out to address the different factors which could make a difference on the speckle contrast and their role in such systems.</p>

<p>Polarization Effects in Wavelength Converters based on Semiconductor Optical Amplifiers</p>

<p>In this project it has been focused on the use of a 7.42 um, 4 mW Quantum Cascade Laser in trace gas detection spectroscopy. Norsk Elektro Optikk (NEO) is in possession of a Nanoplus G2102/DFB2/5-12 QCL laser, that can be used in spectroscopic detection of H2O, CO2 and SO2 It has been attempted to construct a setup that can be used for spectroscopic measurements using a self constructed current driver module to produce current pulses for the QCL. The QCL is operated in pulsed mode, with pulses of <500 ns width, and a 1 kHz pulse repetition frequency. Temperature control of the laser has been conducted with a LaserGas II SP monitor module, and temperature has been kept at 280 K during testing. Initially, various test have been conducted to ensure the general functionality of the driver module, and to avoid damage to the QCL. Two different solutions for the transmission line from the driver to the QCL have also been examined, and it has been concluded that the current pulses supplied to the laser are of good quality with minor broadening and short rise/fall times. Furthermore an I-V characteristic for the laser has been produced by incrementing the laser driving current, and measuring the corresponding laser voltage. Measurements of the laser output power have been conducted using a CaF2 collimating lens to focus the laser beam onto a PVI-2TE-8 Vigo photovoltaic detector from Vigo Systems S.A. It has proved difficult to obtain a good signal from the detector, with the maximum voltage measured across a 50Ω shunt resistor being 3 mV. This is 100-200 mV less than what should be expected. Various methods of noise reduction have been applied to improve the detected signal, none have however provided any noticeable improvements. Several possible reasons for the generally low output have been examined.</p>

<p>This Master’s thesis documents a new test method for detection of small delay faults in FPGA routing network. The main purpose of the test is accurate detection of faults in all parts of the network. The second aim is minimizing test application time. The work of the thesis consisted of four parts. First, a literature study was performed to get background knowledge of FPGA architecture and basics of testing. Second, detection accuracy was defined and measured in SPICE for test paths with different number of fan-out. Third, test configurations were developed. And finally, detection accuracies for the proposed test method were calculated. The SPICE measurements were performed on an interconnect model of FPGA. They revealed that detection accuracy of defects tested by branches of a test path is less than detection accuracy of defects tested by stems of a test path. In addition, it was observed that detection accuracy is best in the beginning of a test path. In the proposed test method detection accuracy is improved by testing all segments outside switch matrices by test path stems, and applying test patterns to all bidirectional segments in both directions. A comparison to two previous test methods showed that the proposed test method is more accurate while keeping the same number of test configurations. The detection accuracy can be improved further by allowing more test configurations.</p>

<p>Cosine Modulated Filter Banks Systems in the Presende of Multipath Transmission</p>

<p>As broadcasted television is changing from analogue to digital transmission, the television industry has to adapt itself for a new reality. Digitization opens for a wide array of new ways of watching television, where interactivity and mobility are paramount. The difference in the experience lies in the interactive part, inviting the user to take part in what happens on the mobile screen. What the mobile telephone lacks in screen size it can now make up for with its interactive potential. Instead of just watching television, the user now interacts with it. As a result, the television experience can be tailored to suit consumers with different requirements. In this study I look at true-time broadcasted television to handheld devices over the standards achieved in Europe and Korea today, DVB-H and T-DMB, and how interactivity between content provider and end-user can be achieved. I also look into how metadata plays a crucial role in interactive television, and the means to utilize metadata to favor the end-user’s demands according to standards such as XML, MPEG and Tv-Anytime. By supplying metadata to i.e sport or reality shows, and hence creating interactivity between content provider and end-user, a new marked for television is made possible. Electronic program guides (EPGs), teletext and weather forecasts for handhelds are examples of ways that metadata can be utilized to create an interactive experience for the end-user.</p>

<p>Give an introduction to the proposed double CubeSat system and an overview of communication requirements and the propagation characteristics that influence the link budget. Based on the above findings, derive requirements for the ground station antenna. Emphasize simplicity and easy construction and propose an antenna system that may meet the requirements. Investigate it theoretically with available software to optimize its dimensions. A scale model of the antenna should finally be built and its main properties measured in an anechoic chamber.</p>

<p>When new transistor technology is used in a microcontroller design, the transistors become smaller. They cannot withstand the same voltages as older technology, because of their size. The automotive industry still uses 5V as a standard voltage, and the automotive industry is a major costumer for microcontroller companies. The microcontroller must therefore be able to use5V. This must be done without the need of external voltage regulator. To still be a supplier to the automotive industry, the AVR needs to be able to withstand voltages up to 5.5V. The main problem with the new transistor technology is the leakage currents. Traditionally, the CMOS devices have used power only when during switching of logical levels. This is no longer true, since the leakage currents have become so large. When using new transistor technology, the dynamic power usage will be reduced, but the total power usage will be increased, if nothing is done to prevent it. One solution to this is to make a multiple power domain microcontroller. The idea is that one power domain can withstand voltages up to 5.5V. The microcontroller then uses an internal voltage regulator to scale down the voltage to a suitable level. The low voltage area will then have a suitable voltage level, which reduces both the dynamic- and leakage power usage. The different voltage domains uses different clock sources, so communicating between them requires both level shifters to deal with the different voltage levels, and synchronization logic to prevent metastability. This assignment uses two voltage domains, VIO and VCORE. Since voltage regulators are quite inefficient, it is most efficient to use only two domains. The VCORE domain contains most of the digital logic of the microcontroller, such as the CPU, SRAM and timers. This domain uses a high-speed clock source, and a VCORE data bus to communicate between each other. To communicate with the VIO domain, the data bus is connected to the VIO data bus through an asynchronous communication scheme block. This is because the VIO domain uses a low speed clock source. The usage of individual clock sources prevents clock skew problems that may occur when passing level shifters, and there is power saving by using only a low speed clock source on the VIO domain. The VIO domain contains the Power Management Unit (PMU). The PMU shall control the power usage of the microcontroller. During active mode, the PMU can set unused modules in sleep mode, or shut them completely off. Most of the power savings are during sleep mode though. This is because a microcontroller such as the AVR spends most of the time in sleep mode. To reduce the power usage in sleep mode, the leakage currents needs to be reduced. The best way of doing so is to disconnect the power from the circuits. If the voltage regulator is disconnected, and all the inputs are set to high impedance, the VCORE domain is completely disconnected from the power, and uses absolutely no power. An asynchronous wake up circuit is designed to make it possible to wake up the microcontroller from a sleep mode without the usage of synchronized digital logic. Then the low frequency oscillator can be turned off, and even more power is saved. The major disadvantage of the multiple power domain solution is the start up time from a sleep mode. If the power to the low voltage area is disconnected, the start up requires that all the capacitors become charged before the chip can start running again. The oscillator is shut off, and it takes time to stabilize the oscillator. Especially since the oscillator requires some stability in the voltage, and the voltage may not stable until the capacitors are charged. Simulations shows that the multiple power domain solution has great potential of power saving. The proposed asynchronous wake up circuit uses only 1.2275nA. This is significantly smaller than the AVR uses in the deepest sleep mode today. To get a secure microcontroller, a reset circuit has to be on to be able to reset the AVR if necessary. The power usage of the reset circuit used today is confidential Atmel information, and cannot be published in this assignment. By looking at the data sheet of a pico power circuit of the AVR, the ATmega329p, one can see that in the deepest sleep mode, the microcontroller uses 40nA at 1.8V. By assuming that the reset circuit does not use more that half of this current, the total amount of power that saved during a sleep mode by using the multiple power domain solution is about 47%.</p>