ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / This paper introduces a frequency scan/following scan twoway carrier acquisition method for USB and its following scan slope decision algorithm. Some measures are used to improve twoway acquisition speed such as selecting initiation direction and returning to zero in the shortest path, which can be implemented by software. Theoretic analysis, mathematical expression, design method and experiment results are provided. Practical engineering application shows the twoway acquisition using this new method has many advantages such as fast speed, low cost and programmability. The method has been used in Chinese USB system widely.

A powerful technique is presented for joint blind channel estimation and carrier offset method for code- division multiple access (CDMA) communication systems. The new technique combines singular value decomposition (SVD) analysis with carrier offset parameter. Current blind methods sustain a high computational complexity as they require the computation of a large SVD twice, and they are sensitive to accurate knowledge of the noise subspace rank. The proposed method overcomes both problems by computing the SVD only once. Extensive simulations using MatLab demonstrate the robustness of the proposed scheme and its performance is comparable to other existing SVD techniques with significant lower computational as much as 70% cost because it does not require knowledge of the rank of the noise sub-space. Also a kernel based equalization for CDMA communication systems is proposed, designed and simulated using MatLab. The proposed method in CDMA systems overcomes all other methods.

The objective of this work is to develop an effective TCAD based hot-carrier degradation model in predicting the damage that a SiGe HBT undergoes as it is stressed across bias, time and temperature.

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / The four-quadrant frequency discriminator (FQFD) plays an important role in GPS receivers for carrier synchronization. This paper presents a detailed study of the operating principle of the FQFD, and the acquisition performance degradation due to the gain fluctuation of the FQFD is discussed. A modified FQFD called the enveloped-four-quadrant frequency discriminator (Enveloped-FQFD) is proposed, which introduces an envelope calculator on the basis of the FQFD. Performance comparison of the FQFD and the Enveloped-FQFD is given through theoretical analysis and computer simulation. Simulation results show that by employing the Enveloped-FQFD, a quicker pull-in process and a wider threshold than the FQFD can be achieved, while the additional hardware costs are trivial.

Field-effect transistors (FET) based on graphene as channel has extraordinaryproperties in terms of charge mobility, charge carrier density etc. However, there aremany challenges to graphene based FET due to the fact graphene is a monolayer ofatoms in 2-dimentional space that is strongly influenced by the operating conditions.One issue is that the Dirac point, or K-point, shifts to higher gate voltage whengraphene is exposed to atmosphere. In this study graphene field-effect transistors(GFET) based on commercially available CVD graphene are electrically characterizedthrough field effect gated measurements. The Dirac point is initially unobservable andlocated at higher gate voltages (>+42 V), indicating high p-doping in graphene.Different treatments are tried to enhance the properties of GFET devices, such astransconductance, mobility and a decrease of the Dirac point to lower voltages, thatincludes current annealing, vacuum annealing, hot plate annealing, ionized water bathand UV-ozone cleaning. Vacuum annealing and annealing on a hot plate affect thegated response; they might have decreased the overall p-doping, but also introducedDirac points and non-linear features. These are thought to be explained by localp-doping of the graphene under the electrodes. Thus the Dirac point of CVDgraphene is still at higher gate voltages. Finally, the charge carrier mobility decreasedin all treatments except current – and hot plate annealing, and it is also observed that charge carrier mobilities after fabrication are lower than the manufacturer estimatesfor raw graphene on SiO2/Si substrate.

published_or_final_version / abstract / Biochemistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Botany / Master / Master of Philosophy

published_or_final_version / abstract / Pathology / Master / Master of Philosophy

No description available.

This thesis contains an experimental and theoretical study of the response of a plasma to the motion of the positive space-charge sheath which bounds it. It is known theoretically that, if a sheath edge is moved at a speed less than the speed of ion acoustic waves, a region of ion rarefaction propagates into the plasma at the ion acoustic speed. In the past, difficulty has been encountered with the theory of ion acoustic wave generation from moving sheath edges, where compressions are necessary in addition to rarefactions. The initial conditions of many previous calculations omit the formation of a steady-state presheath where ions are accelerated to form the sheath. Some calculations are described which include the effects of an initial presheath by constructing a one-dimensional plasma solution where a production term balances the losses of ions to the walls. The plasma response to the motion of one boundary is found using the method of characteristics with appropriate boundary conditions. Ion rarefaction waves are associated with expanding sheaths while ion 'enhancement' waves (compressive features) are formed on sheath collapse. In each case the wave front moves at the local ion acoustic speed which includes the effects of ion drift. The presence of the presheath is essential to the generation of enhancements. The constructional details of a multidipole device are discussed, and the results of Langmuir probe and ion acoustic wave experiments are used to determine the parameters of a quiescent argon plasma. Some experiments on moving sheaths in such a plasma are then considered. Negative voltage ramps are applied to a plate and the plasma response is measured using sampled probe techniques. As the plate-plasma voltage increases, the ion-rich sheath expands at a speed which depends on the applied voltage waveform. For sheath edge speeds less than the ion acoustic speed, an ion rarefaction wave is formed. As the voltage decreases, the sheath collapses and an ion enhancement wave propagates into the plasma. Both wavefronts are observed to move at the local ion acoustic speed which increases with distance from the plate in agreement with theory.