Modern RF and millimeter-wave communication links call for high-efficiency front end systems with high output power and high linearity to meet minimum transmission requirements. Advanced modulation techniques, such as orthogonal frequency-division multiplexing (OFDM) require a large power amplifier (PA) dynamic range due to the high peak-to-average power ratio (PAPR). This thesis provides the analysis, design, and experimental verification of a high-efficiency, high-linearity S-band Doherty power amplifier (DPA) based on the Class F PA. Traditional Class F PAs use harmonically tuned output matching networks to obtain up to 88.4% power-added efficiency (PAE) theoretically, however the amplifier experiences poor linearity performance due to switched mode operation, typically yielding less than 30dB C/I ratio [1]. The DPA overcomes this linearity limitation by using an auxiliary amplifier to boost output power when the amplifier is subject to a high input power due to its limited conduction cycle. The DPA also provides improved saturated output power back-off performance to maintain high PAE during operation. The DPA presented in this thesis optimizes PAE while maintaining linearity by employing harmonically tuned Class F amplifier topology on a primary and an auxiliary amplifier. A Class F PA is first designed and fabricated to optimize output network linearity – this is followed by a DPA design based on the fabricated Class F PA. A GaN HEMT Class F PA and DPA operating at 2.2GHz are implemented with the PAs measuring 40% and 45% PAE respectively while maintaining a 30dB carrier-to-intermodulation (C/I) ratio on a two-tone test. The PAE is characterized at maximum 21dBm input power per tone and 20MHz tone spacing. When subject to a single 24dBm continuous wave input tone, the Class F PA and DPA output 37dBm and 35.5dBm respectively. The PAs presented in the thesis provide over 30dB C/I ratio up to 21dBm input tones while maintaining over 40% PAE suitable for base station applications.

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As wireless devices and radar systems become more ubiquitous, there is a growing need for wideband multi-standard RF-SOCs. To enable the advantages of multi-standard systems, reconfigurable RF front ends are needed. Because of the large number of RF signals in wideband systems, tunability and linearity become important parameters. Prior work has shown tunable LC filters to be advantageous in the microwave regime. A balanced-to-unbalanced (balun) transformation circuit is required to support the differential nature of a tunable LC filter. An active balun that also performs as a transconductor to drive the LC tank would relax the design requirement for the LNA and remove a passive balun that would have to precede the LNA. This thesis discusses the linearization of active baluns and presents a comparison between two 4 to 7 GHz tunable BPF designs with active baluns implemented in 0.18 μm SiGe BiCMOS technology. Fourth order filtering is achieved by subtracting two 2nd order LC-tanks. This approach allows 3-dB bandwidth to be tunable from 10% to 20%. In each design, a linearized input active balun is employed to drive the LC-tanks from a single-ended input while preserving noise figure and IIP3 performance. Two different linearization techniques are applied for the balun designs. Simulated NF ranges from 7.5 to 13 dB and IIP3 averages about 5 dBm with the peak value of 21 dBm. / Master of Science / As wireless devices and radar systems become more ubiquitous, there is a growing need for Radio Frequency (RF) integrated circuits that can support multiple frequency bands and standards. Because of the large number of RF signals, robust tunability and power handling of the electronics become important parameters. Power handling is important because the amplifier and the filter can generate distortions if the power going through them becomes too high. Prior work has shown integrated tunable inductor-capacitor (LC) resonance based filters to be advantageous in the microwave frequency regime compared to integrated switched capacitor based filters. A balancedto-unbalanced (balun) conversion of the RF signals is needed to support the differential nature of the LC resonators. This thesis discusses transistor-based balun designs that can be integrated into front-end LC filter chips. The goal is to reduce distortion in the filter under the present of large number of RF signals and to keep noise of the circuit in reasonable range. The designs are implemented in 0.18 μm SiGe BiCMOS integrated circuit technology and simulated in commercial computer aided design software; predicted performance is competitive with the state of the art. The fabricated chips will be characterized in future work.

There has been increased interest in exploring high frequency (mm-wave) spectrum (particularly the 30 and 60 GHz ranges), and utilizing silicon-based technology for reduced-cost monolithic millimeter integrated circuits (MMIC), for applications such as WLAN, inter-vehicle communication (IVC) automotive radar and local multipoint distribution system (LMDS). Although there has been a significant increase in silicon-based implementations recently, this area still has significant need for research and development. For example, one microwave/mm-wave front-end component that has seen little development in silicon is the power amplifier (PA). Two potential technologies exist for providing a solution for low-cost microwave/mm-wave power amplifiers: 1) Silicon-Germanium (SiGe) HBT and 2) Complementary metal-oxide semiconductor (CMOS). SiGe HBT has become a viable candidate for PA development since it exhibits higher gain and higher breakdown voltage limits compared to CMOS, while remaining compatible with BiCMOS technology. Also, SiGe is potentially lower in cost compared to other compound semiconductor technologies that are currently used in power amplifier design. Hence, this research focuses on design of millimeter-wave power amplifiers in SiGe HBT technology. The work presented in this thesis will focus on design of different power amplifiers for millimeter-wave operating frequencies. Amplifiers present the fundamental trade-off between linearity and efficiency. Applications at frequencies highlighted above tend to be point-to-point, and hence high linearity is required at the cost of lowered efficiency for these power amplifiers. The designed power amplifiers are fully differential topologies based on finite ground coplanar waveguide (FGC) transmission line technology, and have on-chip matching networks and bias circuits. The selection and design of FGC lines is supported through full-wave EM simulations. Tuned single stub matching networks are realized using FGC technology and utilized for input and output matching networks. Two 30-GHz range SiGe HBT PA designs were carried out in Atmel SiGe2RF and IBM BiCMOS 8HP IC technologies. The designs were characterized first by simulations. The performance of the Atmel PA design was characterized using microwave/mm-wave on wafer test measurement setup. The IBM 8HP design is awaiting fabrication. The measured results indicated high linearity, targeted output power range, and expected efficiency performance were achieved. This validates the selection of SiGe HBT as the technology of choice of high frequency point-to-point applications. The results show that it is possible to design power amplifiers that can effectively work at millimeter-wave frequencies at lower cost for applications such as mm-wave WLAN and IVC where linearity is important and required transmitted power is much lower than in cellular handset power amplifiers. Moreover, recommendations are made for future research steps to improve upon the presented designs. / Master of Science

Radio frequency (RF) receivers are inherently non-linear due to non-linear components contained within the RF front-end such as the low noise amplifier (LNA) and mixer. When receivers operate in the non-linear region, this will affect the system performance due to intermodulation products, and cross-modulation, to name a few. Intermodulation products are the result of adjacent channel signals that combine and create intermodulation distortion of the received signal. We call these adjacent channel signals blockers. Receiving blockers are unavoidable in wideband receivers and their effect must be analyzed and properly addressed. This M.S. Thesis studies the effect of blockers on system performance, specifically the symbol error rate (SER), as a function of the receiver non-linearity figure and the blocking signal power and modulation format. There have been numerous studies on the effect of non-linearity in the probability of true and false detections in spectrum sensing when blockers are present. There has also been research showing the optimal modulation scheme for effective jamming. However, we are not aware of work analyzing the effect of modulated adjacent channel blockers on communication system performance. The approach taken in this paper is a theoretical derivation followed by numerical analysis aimed to quantify the effect of receiver nonlinearity on communication system performance as a function of (1) receiver characteristics, (2) blocking signal powers, (3) signal and blocker modulation format, and (4) phase-synchronized/non-synchronized blocker reception. The work focuses on M-PSK modulation schemes. For high blocker powers and non-linearity, the Es/No (Eb/No) performance loss can be as high as 4.7 dB for BPSK modulated signal and BPSK modulated blockers when received in sync with the desired signal. When blockers have a random phase offset with respect to the desired signal, the performance degradation is about 2 dB for BPSK modulated desired and blocker signals. It was found that for an BPSK transmitted signal with phase-synchronous blockers, the SER (BER) deteriorates the most when the blocking signals are of the same modulation. The effect is reduced, but still significant, as the modulation order of the signal of interest or the blockers, or both increases. / Master of Science / This thesis analyzes the effect of non-linear components in wireless receivers on communication system performance. We consider that two strong radio frequency signals adjacent in frequency to the desired signal enter the receiver and cause signal distortion known as 3rd order intermodulation distortion. We analyze the effect on the symbol error rate (SER) in the presence of two modulated blockers. SER defines the ratio of erroneously detected symbols to the total number of transmitted symbols and is a function of the modulation scheme and radio channel conditions. The SER analysis is done for Phase Shift Keying (PSK) modulated signals and blockers for different receiver types and blocker power levels. This thesis derives the theoretical SER expressions followed by numerical analysis aimed to quantify the effect of receiver non-linearity on communication system performance as a function of (1) receiver characteristics, (2) blocking signal powers, (3) signal and blocker modulation formats, and (4) phase-synchronized/non-synchronized reception of blockers. We justify the need for these new SER expressions and verify them via simulations. The thesis shows that modulated blockers can significantly impact communication system performance if the blockers are strong with respect to the signal of interest and if the device is highly non-linear. The work also shows that the performance degradation is a function of the blocker signal characteristics, but there are ways to overcome this loss by design or management. This has important implications on the management of spectrum in the new shared spectrum bands, where heterogeneous systems and devices will coexist with strong signals coming from nearby transmitters, radars or TV stations, among others.

The intent of this thesis is to investigate student approaches to linearity within a linear algebra context, focusing on definitional, computational, and theoretical skills. Linear algebra’s abstract nature constitutes a major challenge for a significant sector of STEM students, with the course often serving as undergraduates’ first encounter with mathematical proofs and extrapolations. The current student struggle is reflected through the prominent gap in knowledge derived from a lack of a concrete understanding of rudimentary concepts (like linearity), pivotal to student success. As such, this investigation aimed to bridge this gap by considering students’ modes of thinking regarding the elementary notion of linearity to improve the current course delivery and curriculum. Students were given three assessment questions targeting different skills integral to the mastery of linearity. Their responses were categorized using Action, Process, Object, Schema (APOS) and analyzed through Sierpinska’s (2000) proposed modes of thinking. About 26% of the participants responded correctly to question 1, 77% to question 2, and 59% to question 3. The analytic mode proved pivotal, specifically when considering definition application and computational abilities. The synthetic-geometric mode, however, was integral to the practical application of the concept. Further discussion and suggestions regarding the results and their implications on the current structure of linear algebra instruction are provided.

Diss. Stockholm : Handelshögskolan, 2006 S. 1-125 : 4 uppsatser

Made available in DSpace on 2016-06-02T20:09:07Z (GMT). No. of bitstreams: 1 1633.pdf: 1450498 bytes, checksum: 168f73bc76f8080e5335a505cfe3289c (MD5) Previous issue date: 2007-10-25 / Structural analysis of framed structures using discrete method, wherein, splitting them into elements with simplified considerations, can bring not satisfactory results or end up using very high safety coefficient to the structure. With the growth of computing and microcomputers it is feasible the resolution of structures considering all parts, therefore three-dimensional. The scope of this work is to make a physical and geometrical non-linear analysis of three-dimensional framed structures with re-bar elements, which can be joined by monolithic or semi-rigid connection, that is commonly used in Precast concrete structures. In order to reach this aim, has been developed a free software using PASCAL language and structural matrix analysis, adding up concrete physical nonlinear analysis with Branson expression. The geometric non-linear was considered from a present Lagrangean formulation. In both cases, it was used the incremental loading technique, which showed a very interesting relation between the results. In order to consolidate the studied concepts and to validate the developed software, it was dedicated a special attention to the resolution of several samples, comparing them with the given results of other software and also with values from experimental analysis, specially for the semi-rigid connections / A análise de estruturas de forma discretizada, ou seja, separando-a em outras estruturas com considerações simplificadoras, pode conduzir a resultados não satisfatórios ou o emprego de coeficientes de segurança muito grandes. Com o advento da informática e microcomputadores já é viável a resolução de estruturas considerandoas como um todo e portanto tridimensionais. Desta forma, objetivo deste trabalho é realizar a análise não linear física e geométrica de estruturas tridimensionais reticulares compostas por elementos de barra, os quais podem ser unidos por ligações monolíticas ou semi-rígidas, como ocorre para estruturas de concreto pré-moldado. Para atingir esta finalidade, desenvolveu-se um programa livre em linguagem TURBO PASCAL, utilizando-se da análise matricial de estruturas, acrescida da consideração da não linearidade física do concreto a partir da equação de Branson. A não linearidade geométrica foi considerada a partir de uma formulação lagrangiana atualizada. Em ambos os casos, utiliza-se a técnica do carregamento incremental, a qual se mostrou bastante interessante em relação aos resultados obtidos. A fim de consolidar os conceitos estudados e também para validar o programa elaborado, dedica-se especial atenção à resolução de vários exemplos, comparando-se os resultados obtidos com outros programas já devidamente validados, e também com valores obtidos a partir da análise experimental, principalmente para o caso das ligações semi-rígidas