/library/oar/handle/123456789/74221 2025-11-10T22:35:49Z 2025-11-10T22:35:49Z /library/oar/handle/123456789/74901 2021-04-29T04:58:12Z 2018-01-01T00:00:00Z

Title: Beam commissioning and optimisation of the Swiss free electron laser in-vacuum undulators Abstract: The Paul Scherrer Institute is currently commissioning a new research facility called SwissFEL. SwissFEL is an X-ray Free Electron Laser, which aims to produce X-ray pulses covering the wavelength range from 1 Å to 70 Å. Each pulse is just 1 fs to 60 fs long, allowing extremely fast reactions and processes to be investigated. This study aims to provide a framework for the online commissioning and optimisation of the light source on the SwissFEL hard X-ray beamline. The beamline consists of thirteen cascaded undulator units, each providing a variable magnetic field in which electrons are forced to emit X-ray radiation. To control and maximize the radiation, the individual units must operate as one. This requires stringent alignment tolerances, where the magnetic field is known at an accuracy of 10-4, and the radiation from all units adds up coherently. Due to accuracy limitations posed by the laboratory setup, this accuracy can only be achieved through an online procedure by characterising the undulators’ spontaneous radiation. Prior to the online procedure, a number of simulations have been performed to analyse and predict the effect of misalignment, magnetic field errors and radiation incoherence on the spontaneous radiation spectrum. The procedure to identify and decouple these errors during online commissioning was devised from this analysis, in addition to the models required to fit the data and determine the optimised operating conditions. This has been based on techniques used in X-ray FEL facilities that are already in operation, as well as innovative solutions as a result of the findings in this work, particularly in the coherence of the radiation. In this work, the models were tested with added electron beam energy jitter, which proved their efficacy under online measurement conditions. In this dissertation, the tools to interface with the equipment and perform the measurement procedures were also developed, and verified with beam measurements. The alignment procedure was verified with beam as part of this dissertation, resulting in significant FEL improvements. Magnetic field and radiation coherence have been optimised for one K value, for which minor adjustments were required. The procedure was confirmed to be effective and practical to be used for further measurements required to fully optimise the magnetic characterisation of the undulator and magnetic components on the undulator cell. Description: M.SC.ICT MICROELECTRONICS&MICROSYSTEMS

2018-01-01T00:00:00Z /library/oar/handle/123456789/74894 2021-04-29T04:57:26Z 2018-01-01T00:00:00Z

Title: Design of a RF MEMS tunable inductor Abstract: The continuous development and improvement of Integrated Circuit (IC) fabrication processes along with the decreasing feature sizes, enables the miniaturisation of electronic devices, thus permitting to integrate more wireless communication standards within the same device. This in turn requires that the components employed within the circuitry are able to function properly across multiple frequency bands. In addition, these circuits need to consume less power while obtaining a higher performance at a lower cost. A possible approach to meet these demanding requirements is to use high performance tunable passive devices within circuits. In this way a single component can be utilised across a wider frequency range and allow for more exibility. In particular, the work presented in this dissertation focuses on the design and simulation of a Micro Electro Mechanical Systems (MEMS) thermally actuated tunable inductor using the MetalMUMPs process. A variety of applications can utilize such a device since it would allow for a circuit to operate in a wider range of frequencies. The inductor structure considered in this dissertation was aimed to be tunable such that its value is controlled according to the actuation applied. Initially, the mechanical aspects of the structure need to be considered in order to ensure that the mechanical properties of the various materials used in the fabrication process are not altered permanently by the actuation applied. In so doing, the range of actuation applied is determined. Three main mechanical properties to be taken into consideration are the temperature such that the melting temperature of the materials is not exceeded, the displacement achieved through the actuation applied, and the stresses in the materials. After determining the limits due to the mechanical aspects, the electrical properties such as the inductance, the quality factor, and the tuning range can be determined at the di erent applicable actuations. In this dissertation an inductor structure based on a single loop formed from two beams was analysed and the variation of the inductance and how well it operates at di erent frequency values were found after having determined the steady state mechanical response of the system. Simulations were performed and the results were compared to the applicable analytical models both for the mechanical and electrical counterparts so as to check out the performance for the structure implemented in both aspects. In this way the range of voltages applied on the thermal actuator implemented was rst determined, after which the displacement of the beams was found. From all these, the electrical parameters of the structure, particularly of the inductance, the tuning range, and the quality factor were determined across a wide frequency range and so the frequency of operation was also determined. Description: M.SC.ICT MICROELECTRONICS&MICROSYSTEMS

2018-01-01T00:00:00Z /library/oar/handle/123456789/74871 2021-04-29T04:56:32Z 2018-01-01T00:00:00Z

Title: Analysis, design and characterisation of comb-actuated MEMS micro-mirror for raster and Lissajous scanning Abstract: This dissertation focuses on the simulation, characterisation and design of MEMS scanning micro-mirrors intended for micro-display applications such as pico-projectors and head-up displays in vehicular systems. An insight to the architecture and device operation behind MEMS scanning micromirrors is given, highlighting the requirements of these devices whilst considering the applications these types of devices are implemented for. The fabrication processes carried out to manufacture such devices are discussed, whilst keeping in mind the advantages and disadvantages behind the actuation principles that are used to actuate the micro-mirror for operation. A detailed analysis on the electromechanical characteristics of a linear micro-mirror for raster-type scanning provided by ST Microelectronics is provided. The performance of the electrostatic comb drive actuation together with the mechanical characteristics of the micro-mirror design were evaluated using theoretical calculations and numerical simulations. Finite Element (FE) simulations for modal, mechanical and electrostatic analyses were performed using CoventorWare 10. Results were compared against measurements undertaken using an electromechanical probing station and a MOEMS optical test bench. The relevant methodologies considered for the analysis of the linear micro-mirror were applied to develop a novel design of a single layer two-directional comb-actuated MEMS scanning micro-mirror aimed for Lissajous scanning with a target optical resolution of 800x600 (SVGA). A verification step on a reported SOIMUMPS 1D micro-mirror was carried out to verify the operation of 2D micro-mirror scanners having one structural layer. Description: M.SC.ICT MICROELECTRONICS&MICROSYSTEMS

2018-01-01T00:00:00Z /library/oar/handle/123456789/74828 2021-04-28T05:08:31Z 2018-01-01T00:00:00Z

Title: Modelling and simulation of a PLL-based transmitter for GSM Abstract: Conventional transmitters for the global standard of mobile communication (GSM) use quadrature amplitude modulation (QAM) with in-phase (I) and quadrature (Q) base-band signals, mixed with carrier frequency signal from a local oscillator. This technique is complex, costly and power hungry due to the number of mixers and digital to analogue converters used to generate the I and Q signals. A more elegant GSM transmitter architecture utilises direct modulation of a high resolution sigma-delta frequency synthesizer and eliminates the need of I and Q base-band signals. The objective of this dissertation was to efficiently model such a transmitter architecture and facilitate the design and simulation prior to circuit implementation. A low cost Gaussian minimum shift keying (GMSK) technique is used, though this architecture is suitable for any continuous phase constant envelope modulation. The Gaussian filter was designed using an efficient look-up table implementation based on Feher’s filter. This implementation reduces the size requirement of the read-only memory by 50% with the use of control logic and encoder blocks. The proposed technique employs a phase-locked loop (PLL) based frequency synthesizer, used to control the phase and instantaneous frequency of the output signal. This design is suitable only for narrow-band modulation as the PLL closed-loop bandwidth is designed to be narrow in order to satisfy PLL noise requirements. The architecture is modelled using Simulink which helps in determining and optimising the hardware specifications necessary for this design. Description: B.SC.(HONS)COMPUTER ENG.

2018-01-01T00:00:00Z