Thesis (MScIng)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). "2 September 2009." Includes bibliographical references (p. [139]-148) and index. Also available via the World Wide Web.

<p> Recently, there has been a strong trend in medicine to use implanted electronic devices for diagnostic and/or therapeutic purposes. These devices usually involve a one- or twoway communication link, allowing communication with the implant. One revolutionary implanted system that was recently launched into the healthcare market is the wireless imaging capsule for monitoring the gastrointestinal tract. Among the application-specific design challenges of such a wireless system are the severe constraints on low power and on small physical size. Besides, the allowed power levels of signals due to in-body radiating devices are restricted to very low values due to human safety concerns. To meet the requirements of such a wireless system, highly efficient, small-size, low-power transmitting radio frequency (RF) blocks are needed. </p> <p> This thesis focuses on the design, implementation and measurements of the last two blocks in the transmitter, namely the antenna and the power amplifier (PA). Three PA circuits have been designed and measured, all of class AB topology. The first two PAs operate at 2.4 GHz, while the third is designed for 405-MHz operation. All designs are fully integrated and realized in a standard mixed-signal 0.18 ~m complementary metaloxide- semiconductor (CMOS) process. Measurement results show that at a supply voltage of 1.4 V, the circuits have a maximum drain efficiency of 32% and 40.7% for the 2.4-GHz and the 405-MHz designs, respectively, while providing an output power of 7.2 and 8 dBm to the load. These results greatly outperform similar designs in the literature, proving that class AB PAs, if properly designed, are well-suited for low-power biotelemetry application. </p> <p> A simple layout design approach was developed to minimize the parasitic effects of on-silicon interconnections that cause significant degradation in the performance of RF integrated circuits (RF ICs ). This approach was used to design the layouts of the three PA circuits presented in this work, and the approach was tested on a low-noise amplifier (LNA) operating at 5 GHz, since at such a high frequency the parasitics become more pronounced. Measurements on the LNA circuit show good agreement with simulations. </p> <p> Thus, next to allowing for optimized circuit performance, this approach can shorten the design time of RF ICs by providing very good predictions of performance characteristics. </p> <p> The last part of this thesis deals with the analysis and design of efficient in-body antennas. A study of the use of loop antennas in medical implants was conducted. Simulations and measurements have been used to characterize the radiation performance of loop antennas in terms of their radiation resistance, transmitting bandwidth and biocompatibility. At 405 MHz, the antenna has proven to be efficient in the dissipative biological tissues, to have a wide transmitting bandwidth, and a specific absorption rate (SAR) distribution that is well below the safety limits. To further verify its suitability for in-body operation, a miniature loop antenna was fabricated and measured at 405 MHz and 2.4 GHz. For measurement purposes, two body simulating chemical solutions were prepared in-house to provide the necessary radiation environment. Measurements show that small loop antennas are well matched in the medium and are thus good in-body radiators. </p> / Thesis / Master of Applied Science (MASc)

<p>Measurements are important to specify and verify properties for components, modules and systems. The specifications for a certain figure of merit are usually given in a numerical value or a two dimensional plot. However, there are some devices, like power amplifiers with certain figure of merits that depends on two or more working conditions, requiring a three dimensional plot.</p><p>This thesis presents a measurement method including graphical user interface of three parameters gain, efficiency and distortion when two-tone or WCDMA signals are used as an input to the PA.</p>

The importance of spectral efficiency in mobile communications often requires the use of non-constant-envelop linear digital modulation schemes. These modulation techniques carry signal information in both magnitude and phase, thus they must be linearly amplified to avoid nonlinear signal distortion which is not correctable in a typical receiver. A second difficulty in utilizing these modulation formats is that nonlinear amplification generates out-of-band power (spectral regrowth). Therefore, to achieve both high energy efficiency and spectral efficiency, some forms of linearization must be used to compensate for the nonlinearity of power amplifiers. One powerful technique that is amenable to monolithic integration is digital signal predistortion. Most predistorters try to achieve the inverse nonlinear characteristic of High Power Amplifier(HPA). In this thesis a new multi-stage digital adaptive signal predistorter is presented. The scheme is developed from the direct iterative method with low memory requirement proposed by Cavers [1] in combination with the multi-stage predistortion proposed by Stonick [2]. To make the predistorter more compact a very simple and fast method called the complementary method is proposed. The complementary method has prominent advantages over other digital predistorters in terms of stability of the algorithm, complexity of the algorithm and computational load. / Graduation date: 2001

Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / 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 (April 26, 2007) Vita. Includes bibliographical references.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.

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.

Measurements are important to specify and verify properties for components, modules and systems. The specifications for a certain figure of merit are usually given in a numerical value or a two dimensional plot. However, there are some devices, like power amplifiers with certain figure of merits that depends on two or more working conditions, requiring a three dimensional plot. This thesis presents a measurement method including graphical user interface of three parameters gain, efficiency and distortion when two-tone or WCDMA signals are used as an input to the PA.

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.