This thesis expounds on the application of Doherty Power Amplifiers (DPA) along with baseband Digital PreDistortion (DPD) techniques to tackle the antagonistic demands of high power efficiency and linearity imposed by modern communications. Memoryless modeling is firstly introduced and its limitations when dealing with PAs driven with realistic devices. Therefore, electrical memory effects are explored in greater detail and a mathematical model showing the relation between the various harmonic components in the output and how they can re-mix back into the fundamental band is developed. The importance of the output bias network in the reduction of memory effects is highlighted. A memory polynomial (MP) based DPD is shown to be a good solution for the linearization of wideband DPA which exhibit strong memory effects. To further improve this solution, the complexity of the MP-DPD is reduced. For that, the even-order terms in the MP branches were first removed. Then, the PA memory effects theory was used to further reduce the number of coefficients of the MP-DPD by decreasing the nonlinearity orders in the different branches individually. These two steps allowed for a reduction of the number of coefficients to almost one-third and the conditioning number by three orders of magnitude while maintaining the same linearization capability. This substantially alleviates the requirements on the digital signal processors and the time needed to construct and implement the MP-DPD in real environment. Experimental validation carried out using a 400 Watt DPA, driven with 4-Carrier WCDMA signal, showed excellent linearization capability by achieving an ACPR of better than 50 dBc with a power efficiency of better than 42.4%. Despite this, the depth of the memory effects in the DPA was still significant. While an effort was made to reduce further the memory effects, the discrepancy between the simulated behavior of the DPA and that observed in simulation was significant. In an attempt to rule out the DPA structure as the cause of the discrepancy between the measured results and the behavior predicted in simulation, a single branch class AB PA was designed using the transistor model. The PA behavior was well predicted when driven with a Continuous Wave (CW) signal, however the simulated and measured behavior differed greatly when the PA was driven by a two tone signal. This rendered the desired reduction of the memory effects impossible at the design stage.

This thesis expounds on the application of Doherty Power Amplifiers (DPA) along with baseband Digital PreDistortion (DPD) techniques to tackle the antagonistic demands of high power efficiency and linearity imposed by modern communications. Memoryless modeling is firstly introduced and its limitations when dealing with PAs driven with realistic devices. Therefore, electrical memory effects are explored in greater detail and a mathematical model showing the relation between the various harmonic components in the output and how they can re-mix back into the fundamental band is developed. The importance of the output bias network in the reduction of memory effects is highlighted. A memory polynomial (MP) based DPD is shown to be a good solution for the linearization of wideband DPA which exhibit strong memory effects. To further improve this solution, the complexity of the MP-DPD is reduced. For that, the even-order terms in the MP branches were first removed. Then, the PA memory effects theory was used to further reduce the number of coefficients of the MP-DPD by decreasing the nonlinearity orders in the different branches individually. These two steps allowed for a reduction of the number of coefficients to almost one-third and the conditioning number by three orders of magnitude while maintaining the same linearization capability. This substantially alleviates the requirements on the digital signal processors and the time needed to construct and implement the MP-DPD in real environment. Experimental validation carried out using a 400 Watt DPA, driven with 4-Carrier WCDMA signal, showed excellent linearization capability by achieving an ACPR of better than 50 dBc with a power efficiency of better than 42.4%. Despite this, the depth of the memory effects in the DPA was still significant. While an effort was made to reduce further the memory effects, the discrepancy between the simulated behavior of the DPA and that observed in simulation was significant. In an attempt to rule out the DPA structure as the cause of the discrepancy between the measured results and the behavior predicted in simulation, a single branch class AB PA was designed using the transistor model. The PA behavior was well predicted when driven with a Continuous Wave (CW) signal, however the simulated and measured behavior differed greatly when the PA was driven by a two tone signal. This rendered the desired reduction of the memory effects impossible at the design stage.

Digital predistortion is one of the most cost effective ways among all linearization techniques. However, most of the existing designs treat the power amplifier as a memoryless device. For wideband or high power applications, the power amplifier exhibits memory effects, for which memoryless predistorters can achieve only limited linearization performance. In this dissertation, we propose novel predistorters and their parameter extraction algorithms. We investigate a Hammerstein predistorter, a memory polynomial predistorter, and a new combined model based predistorter. The Hammerstein predistorter is designed specifically for power amplifiers that can be modeled as a Wiener system. The memory polynomial predistorter can correct both the nonlinear distortions and the linear frequency response that may exist in the power amplifier. Real-time implementation aspects of the memory polynomial predistorter are also investigated. The new combined model includes the memory polynomial model and the Murray Hill model, thus extending the predistorter's ability to compensate for strong memory effects in the power amplifier. The predistorter models considered in this dissertation include both even- and odd-order nonlinear terms. By including these even-order nonlinear terms, we have a richer basis set, which offers appreciable improvement. In reality, however, the performance of a predistortion system can also be affected by the analog imperfections in the transmitter, which are introduced by the analog components; mostly analog filters and quadrature modulators. There are two common configurations for the upconversion chain in the transmitter: two-stage upconversion and direct upconversion. For a two-stage upconversion transmitter, we design a band-limited equalizer to compensate for the frequency response of the surface acoustic wave (SAW) filter which is usually employed in the IF stage. For a direct upconversion transmitter, we develop a model to describe the frequency-dependent gain/phase imbalance and dc offset. We then develop two methods to construct compensators for the imbalance and dc offset. These compensation techniques help to correct for the analog imperfections, which in turn improve the overall predistortion performance.

Linearized equations of motion are important in engineering applications, especially with respect to stability analysis and control design. Traditionally, the full, nonlinear equations are formed and then linearized about the desired equilibrium configuration using methods such as Taylor series expansions. However, it has been shown that the quadratic form of the Lagrangian function can be used to directly linearize the equations of motion for discrete dynamical systems. Here, this development is extended to directly generate linearized equations of motion for both continuous and hybrid dynamical systems, where a hybrid system is described with both discrete and continuous generalized coordinates. The results presented require only velocity level kinematics to form the Lagrangian and find equilibrium configuration(s) for the system. A set of partial derivatives of the Lagrangian are then computed and used to directly construct the linearized equations of motion about the equilibrium configuration of interest. This study shows that the entire nonlinear equations of motion do not have to be generated in order to construct the linearized equations of motion. Several examples are presented to illustrate application of these results to both continuous and hybrid system problems.

The beginning of the 21st century sees great development and demands on wireless communication technologies. Wireless technologies, either based on a cable replacement or on a networked environment, penetrate our daily life more rapidly than ever. Low operational power, low cost, small form factor, and function diversity are the crucial requirements for a successful wireless product. The receiver??s front-end circuits play an important role in faithfully recovering the information transmitted through the wireless channel. Bluetooth is a short-range cable replacement wireless technology. A Bluetooth receiver architecture was proposed and designed using a pure CMOS process. The front-end of the receiver consists of a low noise amplifier (LNA) and mixer. The intermediate frequency was chosen to be 2MHz to save battery power and alleviate the low frequency noise problem. A conventional LNA architecture was used for reliability. The mixer is a modified Gilbert-cell using the current bleeding technique to further reduce the low frequency noise. The front-end draws 10 mA current from a 3 V power supply, has a 8.5 dB noise figure, and a voltage gain of 25 dB and -9 dBm IIP3. A front-end for dual-mode receiver is also designed to explore the capability of a multi-standard application. The two standards are IEEE 802.11b and Bluetooth. They work together making the wireless experience more exciting. The front-end is designed using BiCMOS technology and incorporating a direct conversion receiver architecture. A number of circuit techniques are used in the front-end design to achieve optimal results. It consumes 13.6 mA from a 2.5 V power supply with a 5.5 dB noise figure, 33 dB voltage gain and -13 dBm IIP3. Besides the system level contributions, intensive studies were carried out on the development of quality LNA circuits. Based on the multi-gated LNA structure, a CMOS LNA structure using bipolar transistors to provide linearization is proposed. This LNA configuration can achieve comparable linearity to its CMOS multi-gated counterpart and work at a higher frequency with less power consumption. A LNA using an on-chip transformer source degeneration is proposed to realize input impedance matching. The possibility of a dual-band cellular application is studied. Finally, a study on ultra-wide band (UWB) LNA implementation is performed to explore the possibility and capability of CMOS technology on the latest UWB standard for multimedia applications.

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Made available in DSpace on 2014-06-11T19:24:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-07-01Bitstream added on 2014-06-13T19:47:16Z : No. of bitstreams: 1 pereira_gj_me_rcla.pdf: 459083 bytes, checksum: 3845c68530aed83ffa2e07f2437b7007 (MD5) / Universidade Estadual Paulista (UNESP) / Neste trabalho apresentamos um estudo qualitativo do modelo feito por Ronald Ross sobre a propagação da malária em uma comunidade. O modelo encontra-se no artigo “Contribution to the Analysis of Malaria Epidemiology” de Alfred J. Lotka [1] e é dado por um sistema não linear de duas equações diferenciais ordinárias / In this work we present a qualitative study of the model developed by Ronald Ross about the propagation of malaria in a community. The model is presented by the article “Contribution to the Analysis of Malaria Epidemiology” of Alfred J. Lotka [1] and it is given by a nonlinear system of two ordinary differential equations

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This dissertation is concerned with the development of algorithmic approaches for solving the minisum location and location-allocation problems in which the Euclidean metric is used to measure distances. To overcome the nondifferentiability difficulty associated with the Euclidean norm function, specialized solution procedures are developed for both the location and the location-allocation problems. For the multifacility location problem (EMFLP), two equivalent convex differentiable reformulations are proposed. The first of these is formulated directly in the primal space, and relationships between its Karush-Kuhn-Tucker (KKT) conditions and the necessary and sufficient optimality conditions for EMFLP are established in order to explore the use of standard convex differentiable nonlinear programming algorithms that are guaranteed to converge to KKT solutions. The second equivalent differentiable formulation is derived via a Lagrangian dual approach based on the optimum of a linear function over a unit ball (circle). For this dual approach, which recovers Francis and Cabot's (1972) dual problem, we also characterize the recovery of primal location decisions, hence settling an issue that has remained open since 1972. In another approach for solving EMFLP, conjugate or deflected subgradient based algorithms along with suitable line-search strategies are proposed. The subgradient deflection method considered is the Average Direction Strategy (ADS) imbedded within the Variable Target Value Method (VTVM). The generation of two types of subgradients that are employed in conjunction with ADS are investigated. The first type is a simple valid subgradient that assigns zero components corresponding to the nondifferentiable terms in the objective function. The second type expends more effort to derive a low-norm member of the subdifferential in order to enhance the prospect of obtaining a descent direction. Furthermore, a Newton-based line-search is also designed and implemented in order to enhance the convergence behavior of the developed algorithm. Various combinations of the above strategies are composed and evaluated on a set of test problems. Computational results for all the proposed algorithmic approaches are presented, using a set of test problems that include some standard problems from the literature. These results exhibit the relative advantages of employing the new proposed procedures. Finally, we study the capacitated Euclidean distance location-allocation problem. There exists no global optimization algorithm that has been developed and tested for this class of problems, aside from a total enumeration approach. We develop a branch-and-bound algorithm that implicitly/partially enumerates the vertices of the feasible region of the transportation constraints in order to determine a global optimum for this nonconvex problem. For deriving lower bounds on node subproblems, a specialized variant of the Reformulation-Linearization Technique (RLT) is suitably designed which transforms the representation of this nonconvex problem from the original defining space into a higher dimensional space associated with a lower bounding (largely linear) convex program. The maximum of the RLT relaxation based lower bound that is obtained via a deflected subgradient strategy applied to a Lagrangian dual formulation of this problem, and another readily computed lower bound in the projected location space is considered at each node of the branch-and-bound tree for fathoming purposes. In addition, certain cut-set inequalities in the allocation space, and objective function based cuts in the location space are generated to further tighten the lower bounding relaxation. Computational experience is provided on a set of randomly generated test problems to investigate both the RLT-based and the projected location- space lower bounding schemes. The results indicate that the proposed global optimization approach for this class of problem offers a promising viable solution procedure. In fact, for two instances available available in the in the literature, we report significantly improved solutions. The dissertation concludes with recommendations for further research for this challenging class of problems. Data for the collection of test problems is provided in the Appendix to facilitate further testing in this area. / Ph. D.

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