Radio frequency power amplifiers (PAs) are the most challenging part of the design of radio systems since they dictate the overall system's performance in terms of power efficiency and distortion generation. The performance is further challenged by modern modulation schemes which are characterized by highly varying signal envelopes. In order to meet the spectrum mask requirements, PAs are usually operated at high power back-off to ensure linearity, at the cost of efficiency. To tackle this issue, many efficiency enhancement techniques have been presented in the literature. In fact, these techniques do increase the PA power efficiency at back-off, however, efficiency enhancement techniques do not ensure the linearity of the PA. Furthermore, these techniques may lead to additional distortion. On the other hand, several linearization techniques have been developed to mitigate the PA nonlinearity problem and allow the PA to operate at less back-off. Digital Pre-Distortion (DPD) technique is gaining more attention, as compared to other linearization techniques, thanks to its simple concept and advancements in digital signal processors (DSP) and signal converters. DPD technique consists of introducing a nonlinear function before the PA so that the overall cascaded system behaves linearly. It was clear from the literature that this technique showed good performance. Yet, it has primarily been validated using commercial test equipment, which has good capabilities, and far from the real world environment in which this technique would be implemented. Indeed, DPDs would need to be implemented in signal processors characterised by limited resources and computational accuracy. This thesis presents an implementation of several DPD models, namely look-up table (LUT), memoryless polynomial and memory polynomial (MP), on a field programmable gate array (FPGA). A novel model reformulation made this implementation possible in fixed-point arithmetic. Measurements were collected to validate the DPD models' implementation and an improvement of the signal quality was recorded in terms of error vector magnitude (EVM) and adjacent channel leakage ratio (ACLR). As many wireless access technologies must continue to coexist, multi-standard radio systems are required to reduce the cost while maintaining the interoperability. This thesis presents a development platform for multimode radio which comprises mixed-signal modules. The platform provides the capacity for hardware and software development. In fact, the FPGA under investigation allowed for the implementation of a baseband transceiver and DPD schemes. In addition, a software tool was developed as a dashboard to control and monitor the system. The radio system in the platform was optimized through the equalization of the feedback receiver frequency response performed through a simultaneous measurement of the amplitude ripple of the transmitter and receiver. Furthermore, a phase-coherent frequency synthesizer was designed to bring more flexibility by allowing the transmitter's carrier frequency to be different from the receiver's frequency.

Amorphous and crystalline silicon nanocomposites have been shown to act as effective “sensitizers” for erbium ions. In the present work, a series of erbium-doped (0.2 at.%) SiOx:Er films (x = 1 - 1.8) were synthesized by physical vapor deposition and subsequently annealed at temperatures ranging from 400°C to 1100°C to induce phase separation and cluster growth. Silicon nanocluster (Si-NC) and Er3+ photoluminescence intensity spectra and dynamics were investigated as a function of SiOx composition, annealing temperature, pump wavelength and power, and specimen temperature in order to determine characteristic cross-sections and to map the efficiency of the energy transfer process between Si-NCs and Er3+ ions. Additionally, two types of optical waveguides based on SiOx:Er materials were fabricated using conventional CMOS compatible microfabrication processes. Waveguide propagation losses as well as signal absorption and enhancement were investigated under pumping conditions to evaluate the use of SiOx:Er materials as amplifying media. / Communications and Signal Processing

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on February 14, 2008) Vita. Includes bibliographical references.

Thesis (M.S.)--University of Nevada, Reno, 2007. / "May, 2007." Includes bibliographical references (leaves 82-83). Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2007]. 1 microfilm reel ; 35 mm.

Thesis (Ph. D.)--Brigham Young University. Dept. of Electrical and Computer Engineering, 2007. / Includes bibliographical references (p. 117-121).

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 159-163). Also available via the Internet.

Thesis (Ph. D.)--Washington State University, December 2008. / Title from PDF title page (viewed on Jan. 15, 2009). "School of Electrical Engineering and Computer Science." Includes bibliographical references (p. 60-61).

Thesis (Ph.D.) - University of St Andrews, April 2007.

Thesis (M.S.)--Rochester Institute of Technology, 1984. / Typescript. Includes bibliographical references (leaves 128-136).

Thesis (M.S.)--Rochester Institute of Technology, 1990. / Typescript. Includes bibliographical references (leaf [201]).