This thesis discusses and investigates the estimation of carrier offset frequency in orthogonal frequency division multiplexing (OFDM) mobile systems. The investigation starts by using Mobile WiMAX wireless communication specifications described in IEEE 802.16e as the primary system setup. Under this setup orthogonal frequency division multiple access (OFDMA) is used as a physical layer scheme; it also involves the use of pilots in the OFDM symbol for channel estimation. Although OFDM is resistant to multipath fading, it requires a high degree of synchronisation to maintain sub-carrier orthogonality. Therefore the level of performance of the system depends first on the accuracy in estimating the carrier frequency offset and then the estimation of the channel. Maximum likelihood estimator is used for estimating carrier frequency offset; its performance under different conditions for example SNR, number of virtual carriers needed for estimation etc. are simulated and compared with theoretical results. The optimality of IEEE 802.16e specifications was also examined during the simulations and results analysis.

Comparator is the main building block in an ADC architecture. Main purpose of the comparator is to compare a signal with a reference signal and produce an output depending on whether the input signal is greater or smaller than reference. Many architectures for comparators exist for various purposes. In this thesis, Latched comparator architecture is used for sigma delta modulator. This particular design has two main characteristics that are very important for sigma delta application. First characteristic is the cancellation of memory effect which increases the speed and reliability of the system and the second is, with this architecture, high sensitivity can be achieved. The design and implementation of lathed comparator for sigma delta modulator is presented in this thesis work. Various non-linearities and performance parameters are discussed in detail. Practical implementation and circuit design issues are highlighted to achieve maximum sensitivity along with reasonable speed and accuracy.

Orthogonal Frequency Division Multiplexing (OFDM) plays an important role in the implementation of high data rate communication. In this thesis, the problems of data detection and channel and carrier frequency offset estimation in OFDM systems are studied. <p>Multi-symbol non-coherent data detection is studied which performs data detection by processing multiple symbols without the knowledge of the channel impulse response (CIR). <p>For coherent data detection, the CIR needs to be estimated. Our objective in this thesis is to work on blind channel estimators which can extract the CIR using just one block of received OFDM data. A blind channel estimator for (Single Input Multi Output) SIMO OFDM systems is derived. The conditions under which the estimator is identifiable is studied and solutions to resolve the phase ambiguity of the proposed estimator are given.<p>A channel estimator for superimposed OFDM systems is proposed and its CRB is derived. The idea of simultaneous transmission of pilot and data symbols on each subcarrier, the so called superimposed technique, introduces the efficient use of bandwidth in OFDM context. Pilot symbols can be added to data symbols to enable CIR estimation without sacrificing the data rate. Despite the many advantages of OFDM, it suffers from sensitivity to carrier frequency offset (CFO). CFO destroys the orthogonality between the subcarriers. Thus, it is necessary for the receiver to estimate and compensate for the frequency offset. Several high accuracy estimators are derived. These include CFO estimators, as well as a joint iterative channel/CFO estimator/data detector for superimposed OFDM. The objective is to achieve CFO estimation with using just one OFDM block of received data and without the knowledge of CIR.

The thesis uses an up-down conversion architecture to realize a wideband frequency synthesizer for digital video broadcasting (DVB) transmission system. At first, the theoretical analysis of this architecture is performed to understand the mechanism to suppress the phase noise in an optimal way. Then, the simulations using Matlab and ADS are carried out to predict the phase noise performance. Based on the above efforts, a 50 MHz ~ 1 GHz wideband frequency synthesizer hybrid circuit is implemented and its phase noise performance, corresponding to different choices of the reference sources, is finally discussed. The second part of this thesis is to extend the up-down conversion architecture to an offset phase-locked loop (PLL) architecture for wideband frequency synthesizers. The difference from the conventional offset PLLs is the phase locking of the signal at either the sum or the difference frequency of two voltage-controlled oscillators (VCOs) to the reference source for the purpose of wideband operation. The phase noise analysis of the proposed offset PLL architecture is provided. In the experiments, a 300 MHz ~ 3.6 GHz wideband frequency synthesizer hybrid circuit is implemented to verify the analyzed phase noise results. In addition, a CMOS wideband frequency synthesizer chip using the proposed offset PLL architecture has been realized. Moreover, another two CMOS wideband frequency synthesizer chips are included in this thesis. It is worth mentioning that the VCOs in these two frequency synthesizer chips use the switched capacitor and inductor techniques to achieve a wideband operation.

This study is to improve the coupling efficiency between 980nm high-power pump laser diode and single-mode fiber. In this study, we use the third generation of fiber grinding machine which is designed by Cheng Shiu University, professor Ying-Chien Tsai. This machine is fully automatic. we use it to fabricate the hyperbola microlenses. The advantages about hyperbola microlenses structure are a single-step fabrication, grinding steps to simplify, reduce the grinding time and will greatly reduce the offset of fiber. In the fusing procedure, the slight arc fusion was mainly applied for fine polishing merely instead of reshaping for the reason that the fabricated hyperbola fiber endface was very close to the ideal shape. The fabrication reproducibility and yield increase, and can reduce the cost of grinding. The fiber end shape is similar to the math on the hyperboloid, and the length of the axis of the hyperboloid profile shows a hyperbola. By mathematical properties of hyperbola, we derivation the parameter of radius of curvature for hyperbola microlenses. The definition of the radius of curvature of the hyperbolic vertex and the mode field diameter (the MFD) = 4.2£gm point of intersection with the hyperbola, the characteristics of the formation of this three o'clock round the curvature is the radius of curvature we have said. The radius of curvature (R) is a semi-consistent axial length (a) and two progressive line angle (£c) function, it means we can through the control of ¡§a¡¨ and £c to control the R, but £c is fixed after grinding process. So we choose control parameter ¡§a¡¨ by fusing process, via control ¡§a¡¨ to achieve the purpose of the control R. By various fusing parameters to adjust the gain of ¡§a¡¨, we can control the R in an ideal 2.6-2.8£gm. This process indeed improves the coupling efficiency. This method gives a low offset of the fiber it easier for more than 80%. And larger offset of the fiber by this method can achieve to 70% even 80%.

Static performance and rotordynamic coefficients are provided for a rocker-pivot, tilting-pad journal bearing with 50 and 60 percent offset pads in a load-between-pad configuration. The bearing uses leading-edge-groove lubrication and has the following characteristics: 5-pads, 101.6 mm (4.0 in) nominal diameter, .0814 - .0837 mm (.0032 - .0033 in) radial bearing clearance, .25 to .27 preload, 60.325 mm (2.375 in) axial pad length. Operating conditions included loads from 0 to 3101 kPa (450 psi) and speeds from 7 to 16 krpm. Dynamic tests were conducted over a range of frequencies to obtain complex dynamic stiffness coefficients as functions of excitation frequency. For most test conditions, the direct real dynamic stiffnesses were well fitted with a quadratic function with respect to frequency. This curve fit allowed for the stiffness frequency dependency to be captured by including an added mass matrix [M] to a conventional [K][C] model, producing a frequency independent [K][C][M] model. The direct imaginary dynamic stiffness coefficients increased linearly with frequency, producing frequency independent direct damping coefficients. Compared to the 50 percent offset, the 60 percent offset configuration’s direct stiffness coefficients were larger at light unit loads. At high loads, the 50 percent offset configuration had a larger direct stiffness in the loaded direction. Negative direct added-mass coefficients were regularly obtained for both offsets, especially in the unloaded direction. Added-mass magnitudes were below 32 kg for all test cases. No appreciable difference was measured in direct damping coefficients for both pivot offset. A bulk-flow Navier-Stokes CFD code provided rotordynamic coefficient predictions. The following stiffness and damping prediction trends were observed for both 50 and 60 percent offsets. The direct stiffness coefficients were modeled well at light loads and became increasingly over-predicted with increasing unit load. Stiffness orthotropy was measured at zero and light load conditions that was not predicted. Direct damping predictions in the loaded direction increased significantly with unit load while the experimental direct damping coefficients remained constant with load. The direct damping coefficients were reasonably modeled only at the highest test speed of 16 krpm. Experimental cross-coupled stiffness coefficients were larger than predicted for both offsets, but were of the same sign and considerably smaller than the direct coefficients.

A successive interference cancellation (SIC) structure is proposed for multiuser interference cancellation (MUI) due to carrier frequency offsets (CFOs) in the uplink of orthogonal frequency division multiple access (OFDMA) systems. The proposed architecture adopts a circular convolution to suppress the impacts caused by CFOs. This paper demonstrates that, with 2 iterations, the SIC has better performance than that of the parallel interference cancellation (PIC), but system complexity is only 1/2K, where K is the number of users in the uplink of OFDMA system. This study also shows that system complexity can be significantly reduced if proper approximation is made.

This paper is divided into two parts, experiments and finite element simulations. In experiments, the effects of various rolling conditions such as roll rotational speed, reduction, upon entrance and exit axial velocities, entrance and exit rotational speeds, twisting angle of rolled products are investigated. Experiments with roll rotation and planetary rotation are carried out to check the validity of the results obtained by roll rotation only. In finite element simulations, DEFORM 3D is used to simulate planetary three-roll rolling. The rolling torque, the distance between spirals, and the shape are analyzed, and the analytical results are compared with experimental results.

This dissertation analyzes the basis for and magnitudes of discount factors based on the characteristics of greenhouse gas emission (GHGE) offsets that are applied to the GHGE reduction projects, concentrating on agricultural projects. Theoretical approaches to discount factors, estimation and incorporation of discount factors procedures are developed. Discount factors would be imposed by credit purchasers due to noncompliance with regulatory program of the credits with GHG program including consideration of shortfall penalties and limited durations. Discount factors are proposed for (i) additionality, (ii) leakage, (iii) permanence, and (iv) uncertainty. Additionality arise when the region where an AO project is being proposed would have substantial adoption of the AO practice in the absence of GHG programs (business as usual GHGE offset). Leakage arises when the effect of a program is offset by an induced increase in economic activity and accompanying emissions elsewhere. The leakage effect depends on demand and supply elasticities. Permanence reflects the saturation and volatility characteristics of carbon sequestration. Carbon is stored in a volatile form and can be released quickly to the atmosphere when an AO practice is discontinued. The permanence discount depends on the project design including practice continuation after the program and the dynamic rate of offset. Also, consideration of multiple offsets is important. Uncertainty arises due to the stochastic nature of project quantity. The uncertainty discount tends to be smaller the larger the size of the offset contract due to aggregation over space and time. The magnitude of these discounts is investigated in Southeast Texas rice discontinuation study. The additionality and the leakage discounts are found to play an important role in case of rice lands conversion to other crops but less so for pasture conversions and yet less for forest conversions. The permanence discount is important when converting to other crops and short rotation forestry. When all discounts are considered, rice lands conversion to forest yields claimable credits amounting to 52.8% ~ 77.5% of the total offset. When converting rice lands to pasture, the claimable credits 45.1% ~ 64.2%, while a conversion of rice lands to other crops yields claimable credits 38.9% ~ 40.4%.

This thesis presents a bio-signal recording system with offset cancellation and a low power comparator. The recording of bio-signal requires high-gain amplification before recording, to match the input to the range of the analog to digital converter (ADC); interference could be a problem if it causes the amplifier to reach saturation, leaving the recording inoperable (i.e., blank) until it returns to its normal state. The proposed system can monitor the amplifier output, and reset the amplifier output to a point near the center of its dynamic range before the amplifier output leaves its dynamic range. The proposed system provides discrete compensation voltages to cancel the offset voltage, and thereby avoids the shortcomings of conventional filters. Furthermore, a low power and low offset voltage comparator for low current operation is proposed. It is suitable for the clock controller in a sampled bio-signal acquisition system. The measured current consumption of the comparator is less than 130 nA, and the offset voltage is 2 mV. The proposed recording system and comparator have been implemented in the TSMC (Taiwan Semiconductor Manufacturing Company) 0.35£gm 2P4M CMOS process technology to verify the simulation results as well as the correctness of the proposed architecture.