Hybrid Digital/RF Envelope Predistortion Linearization for High Power Amplifiers in Wireless Communication Systems Wangmyong Woo 151 Pages Directed by Dr. J. Stevenson Kenney The objective of this research is to implement a hybrid digital/RF envelope predistortion linearization system for high-power amplifiers used in wireless communication systems. It is well known that RF PAs have AM/AM (amplitude modulation) and AM/PM (phase modulation) nonlinear characteristics. Moreover, the distortion components generated by a PA are not constant, but vary as a function of many input conditions such as amplitude, signal bandwidth, self-heating, aging, etc. Memory effects in response to past inputs cause a hysteresis in the nonlinear transfer characteristics of a PA. This hysteresis, in turn, creates uncertainty in predictive linearization techniques. To cope with these nonlinear characteristics, distortion variability, and uncertainty in linearization, an adaptive digital predistortion technique, a hybrid digital/RF envelope predistortion technique, an analog-based RF envelope predistortion technique, and a combinational digital/analog predistortion technique have been developed. A digital adaptation technique based on the error vector minimization of received PA output waveforms was developed. Also, an adaptive baseband-to-baseband test system for the characterization of RF PAs and for the validation of linearization algorithms was implemented in conjunction with the adaptation technique. To overcome disadvantages such as limited correction bandwidth and the need for a baseband input signal in digital predistortion, an adaptive, wideband RF envelope predistortion system was developed that incorporates a memoryless predistortion algorithm. This system is digitally controlled by a look-up table (LUT). Compared with conventional baseband digital approaches, this predistortion architecture has a correction bandwidth that is from 20 percent to 33 percent wider at the same clock speeds for third to fifth order IMDs and does not need a digital baseband input signal. For more accurate predistortion linearization for PAs with memory effects, an RF envelope predistortion system has been developed that uses a combination of analog-based envelope predistortion (APD) working in conjunction with digital LUT-based adaptive envelope predistortion (DPD). The resulting combination considerably decreases the computational complexity of the digital system and significantly improves linearity and efficiency at high power levels.

The objective of this thesis was to model the Fuzz Face , a transistor-based guitar distortion effect, digitally at the circuit level, and explore how changes in the discrete analog components change the digital model. The circuit was first simulated using SPICE simulation software. Typically outputs and how they changed based on transistor gains were documented. A test circuit was then constructed in lab to determine true transistor gains. An analog Fuzz Face circuit was then constructed, and physical parameters were recorded. A digital model was then created using MATLAB. Capacitive filtering effects were found to be negligible in terms of the guitar signal and were not modeled. The transistors were modeled using the Ebers-Moll equations. A MATLAB algorithm was written to produce Fuzz Face type distortion given an input guitar signal. The algorithm used numerical techniques to solve the nonlinear equations and stored them in a look-up table. This table was used to process the input clips. The sound of the Fuzz Face was not perfectly modeled, but the equations were found to provide a reasonable approximation of the circuit. Further study is needed to determine a more complete modeling equation for the circuit.

Distributed three-dimensional (3D) graphics applications exhibit both resemblance and uniqueness in comparison with conventional streaming media applications. The resemblance relates to the large data volume and the bandwidth-limited and error-prone transmission channel. The uniqueness is due to the polygon-based representation of 3D geometric meshes and their accompanying attributes such as textures. This specific data format introduces sophisticated rendering computation to display graphics models and therefore places an additional constraint on the streaming application. The objective of this research is to provide scalable, error-resilient, and time-efficient solutions for high-quality 3D graphics applications in distributed and resource-constrained environments. Resource constraints range from rate-limited and error-prone channels to insufficient data-reception, computing, and display capabilities of client devices. Optimal resource treatment with transmission and rendering scalability is important under such circumstances. The proposed research consists of three milestones. In the first milestone, we develop a joint mesh and texture optimization framework for scalable transmission and rendering of textured 3D models. Then, we address network behaviors and develop a hybrid retransmission and error protection mechanism for the on-demand delivery of 3D models. Next, we advance from individual 3D models to 3D scene databases, which contain numerous objects interacting in one geometric space, and study joint application and transport approaches. By properly addressing the properties of 3D scenes represented in multi-resolution hierarchies, we develop a joint source and channel coding method and a multi-streaming framework for streaming the content-rich 3D scene databases toward optimized transmission and rendering scalability under resource constraints.

The use of unproctored internet-based testing for employee selection is widespread. Although this mode of testing has advantages over onsite testing, researchers and practitioners continue to be concerned about potential malfeasance (e.g., cheating and response distortion) under high-stakes conditions. Therefore, the primary objective of the present study was to investigate potential malfeasance effects on the scores of an unproctored internet-based cognitive ability, and a personality test. This was accomplished by implementing a within-subjects design in which test takers first completed the tests as job applicants (high-stakes) or incumbents (low-stakes) then as research participants (low-stakes). The pattern of cognitive ability test score differences was more consonant with a psychometric practice effect than a malfeasance explanation. Thus, the results suggest that, if present, there was no evidence to indicate that wide- scale or systematic malfeasance unduly affected the test scores. This may have been due to the speeded nature of the test, which was used to preempt the potential for widespread cheating. Additionally, the unproctored personality administration resulted in similar mean shifts and similar proportions of test takers being suspected of distorting their responses as that reported in the extant literature for proctored tests. In their totality, these results suggest that an unproctored internet-based administration does not uniquely threaten personality measures in terms of elevated levels of response distortion compared to proctored measures.

In this study, the behavior of pressure in the Rapid Distortion Limit, along with its concomitant modeling, are addressed. In the first part of the work, the role of pressure in the initiation, propagation and suppression of flow instabilities for quadratic flows is analyzed. The paradigm of analysis considers the Reynolds stress transport equations to govern the evolution of a dynamical system, in a state space composed of the Reynolds stress tensor components. This dynamical system is scrutinized via the identification of the invariant sets and the bifurcation analysis. The changing role of pressure in quadratic flows, viz. hyperbolic, shear and elliptic, is established mathematically and the underlying physics is explained. Along the maxim of "understanding before prediction", this allows for a deeper insight into the behavior of pressure, thus aiding in its modeling. The second part of this work deals with Rapid Pressure Strain Correlation modeling in earnest. Based on the comprehension developed in the preceding section, the classical pressure strain correlation modeling approaches are revisited. Their shortcomings, along with their successes, are articulated and explained, mathematically and from the viewpoint of the governing physics. Some of the salient issues addressed include, but are not limited to, the requisite nature of the model, viz. a linear or a nonlinear structure, the success of the extant models for hyperbolic flows, their inability to capture elliptic flows and the use of RDT simulations to validate models. Through this analysis, the schism between mathematical and physical guidelines and the engineering approach, at present, is substantiated. Subsequently, a model is developed that adheres to the classical modeling framework and shows excellent agreement with the RDT simulations. The performance of this model is compared to that of other nominations prevalent in engineering simulations. The work concludes with a summary, pertinent observations and recommendations for future research in the germane field.

Hole-doped manganite La0.7Ca0.3MnO3 (LCMO) was extensively studied because of its colossal magnetoresistance (CMR) characteristic in a magnetic field. Recently, a new member of CMR family La0.7Ce0.3MnO3 (LCeMO), an electron-doped manganite, raises a new wave of attention for possible application in p-n junction. In this present study, LCMO and LCeMO single layer and bi-layer were grown on SrTiO3 (100) substrate by a pulse laser ablation technique. Due to the neutralization at the p-n junction a possible insulating layer with the anti-ferromagnetic (AFM) property is expected. There is no systematically study of this matter up to date, thus, it is worth to systematically investigate the physical properties of this junction. The result indicates the possible neutralization layer exhibits huge resistance comparison with two lateral layers, the bias current is constrained on the limited thickness of the top layer, which implies the neutralization layer forms a depletion layer that block the current to flow through to the bottom layer. Its electric and magnetic properties may similar to the parent compound LaMnO3 with insulating and anti-ferromagnetic characteristics. Separated by this possible layer, the magnetic coupling between lateral layers is weak. However, the possible AFM layer does pin the magnetic moment of the top layer along the direction perpendicular to the substrate that make a distinct magnetoresistance at low magnetic field.

Hole-doped maganite with middle to narrow bandwidth La1-xCaxMnO3 was extensively studied because of its colossal magnetoresistance (CMR) characteristic under a magnetic field. These kind of materials show un- common magnetic and electric properties. The charge order phase only happens to the region x> 0.5, and along with decreasing temperature, its phase goes from para-insulator to charge-ordered then to antiferromagne- tism. In our studies, we apply correlation function of Green¡¦s function to LCMO and get susceptibility of charge and spin. Then we can get the cri- tical value of Coulomb repulsion inside the material by substituting the experimental values of phase transition temperature. This critical values is the key point of charge-ordered. Then we can also get the size of char- ge gap which decides the stability of charge-ordered phase. After know- ing the Coulomb repulsion and charge gap, we can picture the relation of inside and on-site Coulomb repulsion qualitatively while the transition happens. Here the on-site Coulomb repulsion means to the Hund¡¦s coupl- ing between d electrons. And by this we¡¦ll understand the physics inside CMR materials.

With the advances in computer technology and the changing needs of people&rsquo / s daily lives, robots start to offer alternative solutions. As one of these solutions, the branch of humanoid robots emerged as advanced robots that can interact with people. Robot faces are one of the most effective means of interacting with people / since they can express their emotions and reactions through facial mimics. However, the development of realistic robot faces necessitates the knowledge of the trajectories and displacements of actual face mimics. In this study, a setup (both hardware and software), that can be used for tracking critical points on human face while exhibiting mimics, is developed. From the outputs of this setup, the mimic trajectories are going to be extracted. The setup is designed and manufactured to be durable to external effects so that with a single camera calibration procedure the 3D reconstruction can be carried out several times. The setup consists of two webcams that are specially oriented for mimic tracking. The images taken from the cameras are corrected / their features are extracted using image processing algorithms / the centroids of the features are found / correspondence is carried out and the reconstruction is made. This system can also be used for any special point tracking or volumetric measurement purposes.

Distortion (undesired dimension and shape changes) is one of the most important problems of through hardened steel components. During quenching, anisotropic dimensional changes are inevitable due to classical plasticity and transformation induced plasticity. Moreover / various distortion potential carriers are brought into material during production chain. This study consists of analytical, numerical and experimental investigations of quench distortion. In numerical and analytical part, sensitivity analysis of the quenching model, and dimensional analysis of distortion were conducted by utilizing experimentally verified simulations. In sensitivity analysis, effect of uncertainties in input data on simulation results were determined, whereas / in dimensional analysis, the influence of various dimensionless numbers that govern quench distortion were investigated. Throughout the study, gas-nozzle-field quenching of SAE52100 long shafts were simulated. Simulations were performed by commercial finite element analysis software, SYSWELD&reg / . Conceptual results indicate that the most important material properties and dimensionless numbers are the ones that govern volume change. Moreover, those that determine plasticity of austenite significantly affect isotropy of the dimensional changes. When unimportant dimensionless numbers are eliminated, there remain 14 dimensionless combinations that govern the problem. In experimental part of the study / effect of microstructure on distortion behavior of SAE52100 long cylinders with various diameters was investigated. In addition to gas-nozzle-field quenching, salt bath and high speed quenching experiments were performed. In regards to experimental findings, there is a correlation between distortions of long cylinders and machining position with respect to billet.

In this thesis, bit-by-bit power allocation in order to minimize mean-squared error (MSE) distortion of a basic communication system is studied. This communication system consists of a quantizer. There may or may not be a channel encoder and a Binary Phase Shift Keying (BPSK) modulator. In the quantizer, natural binary mapping is made. First, the case where there is no channel coding is considered. In the uncoded case, hard decision decoding is done at the receiver. It is seen that errors that occur in the more significant information bits contribute more to the distortion than less significant bits. For the uncoded case, the optimum power profile for each bit is determined analytically and through computer-based optimization methods like differential evolution. For low signal-to-noise ratio (SNR), the less significant bits are allocated negligible power compared to the more significant bits. For high SNRs, it is seen that the optimum bit-by-bit power allocation gives constant MSE gain in dB over the uniform power allocation. Second, the coded case is considered. Linear block codes like (3,2), (4,3) and (5,4) single parity check codes and (7,4) Hamming codes are used and soft-decision decoding is done at the receiver. Approximate expressions for the MSE are considered in order to find a near-optimum power profile for the coded case. The optimization is done through a computer-based optimization method (differential evolution). For a simple code like (7,4) Hamming code simulations show that up to 3 dB MSE gain can be obtained by changing the power allocation on the information and parity bits. A systematic method to find the power profile for linear block codes is also introduced given the knowledge of input-output weight enumerating function of the code. The information bits have the same power, and parity bits have the same power, and the two power levels can be different.