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<p>Idén med examensarbetet var att konstruera en generell radiolänk med minsta möjliga storlek, som skulle kopplas samman med en redan befintlig konstruktion. Radiokrets CC1100 från Chipcon används tillsammans med mikroprocessor MSP430 från Texas Instruments. För att</p><p>radiomodulen skall klara ett stort inspänningsområde används en spänningsstabilisator XC6202 från Torex. Det färdiga kortet är ett fyralagerskort med komponenter på en sida, med ett helt jordplan. Komponenterna är placerade så att de fyller sin funktion, samtidigt som de upptar minsta möjliga utrymme egentligen kanske detta med ska vara dåtid? . Med hjälp av en nätverksanalysator undersöktes antennanpassningen så att denna erhöll ett värde på nära 50</p><p>W. Radiokretsen programmerades och testades sedan.</p> / <p>The idea behind this project was to construct a general RF-module as small as possible and the RF-module should be able to connect to an existing design. A transceiver from Chipcon, CC1100, was used together with a microprocessor MSP430 from Texas Instruments. To make</p><p>the RF-module handle a wide input voltage range a voltage regulator, XC6202, from Torex was used. The circuit board is a four layer card with one layer ground and components on one side. The components are placed to full fill there purpose and at the same time make the card</p><p>as small as possible. With help from a network analyzer the network to the antenna was examined so it obtained a value near 50 W. The RF-module was programmed and tested with good result, but I didn’t participated.</p>

This thesis discusses microstrip circuits and components with a slotted area on the ground plane. In recent years, various slot geometries have been placed on the ground plane with the purpose of reducing harmonics, producing frequency pass/stop-bands, and enhancing coupling effects. Among several ground slot geometries, a dumbbell shaped slot (DSS) is attractive because of its simple structure and easy analysis. The DSS and its applications to RF/microwave filters are studied and discussed. A lumped equivalent circuit model of the dumbbell shaped ground slot is introduced by utilizing resonator and filter theories. The accuracy of the equivalent circuit model is demonstrated through the comparison of circuit simulations and measurements. A lowpass filter (LPF) using slotted ground structure (SGS) with dumbbell shape is designed and measured to validate its theories. By using SGS techniques presented in this thesis, some other RF/microwave components such as a periodic structure, ultra-wideband bandpass filter (UWB-BPF), and rectenna with SGS-LPF are designed and tested.

Parallel excitation is an emerging technique to improve or accelerate multi-dimensional spatially selective excitations in magnetic resonance imaging (MRI) using multi-channel transmit arrays. The technique has potential in many applications, such as accelerating imaging speed, mitigating field inhomogeneity in high-field MRI, and alleviating the susceptibility artifact in functional MRI (fMRI). In these applications, controlling radiofrequency (RF) power deposition (quantified by Specific Absorption Rate, or SAR) under safe limit is a critical issue, particularly in high-field MRI. This \dissertation will start with a review of multidimensional spatially selective excitation in MRI and current parallel excitation techniques. Then it will present two new RF pulse design methods to achieve reduced local/global SAR for parallel excitation while preserving the time duration and excitation pattern quality. Simulations incorporating human-model based tissue density and dielectric property were performed. Results have show that the proposed methods can achieve significant SAR reductions without enlonging the pulse duration at high-fields.

A graphene field-effect-transistor (GFET) model calibrated with extracted device parameters and a commercial 65 nm silicon MOSFET model are compared with respect to their radio frequency behavior. GFETs slightly lag behind CMOS in terms of speed despite their higher mobility. This is counterintuitive, but can be explained by the effect of a strongly nonlinear voltage-dependent gate capacitance. GFETs achieve their maximum performance only for narrow ranges of V-DS and I-DS, which must be carefully considered for circuit design. For our parameter set, GFETs require at least mu = 3000 cm(2) V-1 s(-1) to achieve the same performance as 65 nm silicon MOSFETs. / <p>QC 20130115</p>

No description available.

This thesis discusses microstrip circuits and components with a slotted area on the ground plane. In recent years, various slot geometries have been placed on the ground plane with the purpose of reducing harmonics, producing frequency pass/stop-bands, and enhancing coupling effects. Among several ground slot geometries, a dumbbell shaped slot (DSS) is attractive because of its simple structure and easy analysis. The DSS and its applications to RF/microwave filters are studied and discussed. A lumped equivalent circuit model of the dumbbell shaped ground slot is introduced by utilizing resonator and filter theories. The accuracy of the equivalent circuit model is demonstrated through the comparison of circuit simulations and measurements. A lowpass filter (LPF) using slotted ground structure (SGS) with dumbbell shape is designed and measured to validate its theories. By using SGS techniques presented in this thesis, some other RF/microwave components such as a periodic structure, ultra-wideband bandpass filter (UWB-BPF), and rectenna with SGS-LPF are designed and tested.

I propose to develop a new method for the synthesis of metal matrix composites (MMC) using aerosol reactants in a radio frequency (RF) plasma torch. An inductivelycoupled RF plasma torch (ICPT) may potentially be designed to maintain laminar flow and a radial temperature distribution. These two properties provide a method by which a succession of metal layers can be applied to the surface of SiC fibers. In particular, the envisaged method provides a means to fully bond any desired metal to the surface of the SiC fibers, opening the possibility for MMCs in which the matrix metal is a highstrength steel. A crucial first step in creating the MMC is to test the feasibility of constructing an ICPT with completely laminar flow in the plasma region. In this work, a magnetohydrodynamic (MHD) model is used along with a computational fluid dynamic (CFD) software package called FLUENT© to simulate an ICPT. To solve the electromagnetic equations and incorporate forces and resistive heating, several userdefined functions (UDF) were written to add to the functionality of FLUENT©. Initially, an azimuthally-symmetric, two-dimensional model was created to set a test baseline for operating in FLUENT© and to verify the UDF. To incorporate coil angle and current leads, a fully three dimensional model UDF was written. Preliminary results confirm the functionality of the code. Additionally, the results reveal a non-mixing, laminar flow outer region for an axis-symmetric ICPT.

Magnetic Resonance Spectroscopy is known as a valuable diagnostic tool for physicians as well as a research tool for biochemists. In addition to hydrogen (which is the most abundant atom with nuclear magnetic resonance capability), other species (such as 31P or 13C) are used as well, to obtain certain information such as metabolite concentrations in neural or muscular tissues. However, this requires nuclear magnetic resonance (NMR) transmitter/receivers (coils) capable of operating at multiple frequencies, while maintaining a good performance at each frequency. The objective of this work is to discuss various design approaches used for second-nuclei RF (radio frequency) coils, and to analyze the performance of a particular design, which includes using inductor-capacitor (LC) trap circuits on a 31P coil. The method can be easily applied to other nuclei. The main advantage of this trapping method is the enabling design of second-nuclei coils that are insertable into standard proton coils, maintaining a near-optimum performance for both nuclei. This capability is particularly applicable as MRI field strengths increase and the use of specialized proton coils becomes more prevalent. A thorough performance analysis shows the benefit of this method over other designs, which usually impose a significant signal-to-noise (SNR) sacrifice on one of the nuclei. A methodology based on a modular coil configuration was implemented, which allowed for optimization of LC trap decoupling as well as performance analysis. The 31P coil was used in conjunction with various standard 1H coil configurations (surface/volume/array), using the trap design to overcome the coupling problem (degraded SNR performance) mentioned above. An analytical model was developed and guidelines on trap design were provided to help optimize sensitivity. The performance was analyzed with respect to the untrapped case, using RF bench measurements as well as data obtained from the NMR scanner. Insertability of this coil design was then verified by using it with general-purpose proton coils available. Phantoms were built to mimic the phosphorus content normally found in biologic tissues in order to verify applicability of this coil for in vivo studies. The contribution of this work lies in the quantification of general design parameters to enable “insertable” second-nuclei coils, in terms of the effects on SNR and resonance frequency of a given proton coil.

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