Radio Frequency (RF) Power Amplifiers are responsible for a considerable amount of the power consumption in the entire transmitter-receiver (transceiver) of modern communication systems. The stringent linearity requirements of multi-standard transceivers to minimize cross-talking effects makes Linear Power Amplifiers, particularly class A, the preferred choice in broadband transceivers. This linearity requirement coupled with the fact that the Power Amplifier operates at low transmit power during most of its operation makes the efficiency of the entire transceiver poor. The limited transceiver efficiency leads to a reduction in the battery life of battery operated portable devices like mobile phones; hence drastically limiting talk time. To alleviate this issue, several research groups propose solutions to improve PA power efficiency. However, these solutions usually have a low efficiency at low power and are mostly limited to narrow bandwidth applications. In this thesis, the efficiency of a class A Power amplifier in wideband wireless standards like WiMax is improved by dynamically controlling the bias current and supply voltage of the PA. An efficient supply modulator based on a switching regulator architecture is proposed for controlling the supply voltage. The switching regulator is found to be slew-limited by the bulky inductor and capacitor used to regulate the supply voltage. The proposed solution alleviates the slew rate limitation by adding a bang-bang controlled current source. The proposed supply modulator has an average power efficiency of 81.6 percent and is suitable for wireless standards with bandwidths up to 20MHz compared to the relatively lower efficiencies and bandwidths of state of the art modulators. A class-A PA is shown to promise an average power efficiency of 21.3 percent when the bias current is controlled dynamically and the supply voltage is varied using the proposed supply modulator. This is a significant improvement over the poor average efficiency of 1.06 percent for a fixed bias conventional linear class A PA. The project has been simulated using the TSMC 0.18 micrometer technology.

Phase locked loops (PLL) are used in many applications. Application examples include clock and data recovery, clock synthesis, frequency synthesis, modulator, and de-modulator. In many circuits, PLL must provide an output clock to follow the input clock closely. For high speed environments, the noises also rise up. Noises mainly come from the power supply and substrate. They produce jitter. A low jitter design is important in PLL circuit. In this thesis, we discuss the Voltage Controlled Oscillator (VCO) which has the largest jitter in PLL system. We propose a low jitter voltage controlled oscillator designed in TSMC 0.35£gm 2P4M Mixed-Signal process technology. We include a regulator to reduce jitter by increasing the VCO PSRR. This structure also provides a high linearity gain (Kvco) which decreases the VCO jitter in the PLL circuit and improve the system stability.

The thesis is composed of two topics : a charger circuit of Li-ion batteries for wireless biomedical systems and a capacitor-less low dropout regulator¡]LDO¡^. The first topic discloses a charger circuit of Li-ion batteries using 2P4M 0.35-£gm CMOS process, which comprises a small bias circuit, a comparator with hysteresis, a transistor voltage divider circuit, a power MOS, and a Li-ion charger with a cut-off voltage and a recharge voltage. The proposed design receives a 13.56 MHz carrier with 5¡Ó0.2 V amplitude to charge the Li-ion batteries with a small constant current. The second topic reveals a low dropout regulator ¡]LDO¡^ without capacitor load and ESR, including a bias circuit, an error amplifier, and a Flipped Voltage Follower circuit generating a stable output voltage independent on different loads. The proposed design improves the input voltage limitation of Flipped Voltage Follower by compensating phase margin such that the proposed design shows a good transient response and stability without any output capacitor. The proposed LDO is implemented by 1P6M 0.18-um CMOS process, which can operate correctly given an input voltage range from 3.3~4.2 V.

Traditional methods of system-on-chip (SoC) power management based on dynamic voltage and frequency scaling (DVFS) is limited by 1) cores/IP blocks sharing a voltage domain provided by off-chip voltage regulators (VR) and 2) slow voltage scaling time \((<0.1V/\mu s)\). This global, slow DVFS cannot track the increasingly heterogeneous, fluctuating performance requirements of individual microprocessor cores and SoC components. Furthermore, traditional off-chip VRs add significant area overhead and component cost on the board. This thesis explores replacing a large portion of existing off-chip VRs with integrated voltage regulators (IVR) that can scale the voltage at a 50 mV/ns rate, which is 500 times faster than microsecond-scale voltage scaling with existing off-chip VRs. IVRs occupy 10 times smaller footprint than off-chip VRs, making it easy to duplicate them to provide per-core or per-IP-block voltage control. This thesis starts by summarizing the benefits of using IVRs to deliver power to SoCs. Based on a simulation study targeting a 1.6W, 4-core SoC, I show that greater than 20% energy savings is possible with fast, per-core DVFS enabled by IVRs. Next, I present two stand-alone IVR test-chips converting 1.8V and 2.4V to 0.4-1.4V while delivering maximum 1W to the output. Both test-chips incorporate a 3-level VR topology, which is suitable for integration because the topology allows for much smaller inductors (1nH) than existing inductor-based buck VRs. I also discuss reasons behind lower-than-simulated efficiencies in the test-chips and ways to improve. Finally, I conclude with future process technologies that can boost IVR conversion efficiencies and power densities. / Engineering and Applied Sciences

Increasing power consumption and heat dissipation are becoming urgent challenges for processors today and in the future. Digital power control architectures in which processors closely interact with voltage regulators are becoming necessary to enhance system energy efficiency. Digital techniques offer advantages such as flexibility, fewer external components and reduced overall cost as compared to conventional analog techniques. The primary objective of this thesis is to develop new digital control architecture for processor voltage regulators with low complexity and high dynamic performance. A digital control technique to naturally implement the desired output impedance is proposed. In this technique, Adaptive Voltage Positioning (AVP) is implemented by generating a dynamic voltage reference and a dynamic current reference to achieve the desired output impedance. A dual-voltage-loop control with dynamic reference step adjustment, non-linear control and a dedicated transient detection circuit is proposed to improve the dynamic performance. The dynamic reference step adjustment method lowers the high speed requirement of reference update clock; the non-linear control minimizes the transient-assertion-to-action delay and maximizes the inductor current slew rate; and the transient detection circuit recognizes the load transient state in a manner adaptive to the amount and slew rate of load transient. Theoretical, simulation and experimental results prove the effective operation and excellent performance of the controller. Finally, the dynamic performance of the voltage regulator with the proposed digital controller under large-step load oscillations is proven by simulation and experimental results. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2008-07-31 13:14:52.149

Harnessing the control of flowering time in sorghum bicolor has been essential to programs committed to the development and improvement of this crop. The success of such programs was dependent on the utilization of six Maturity Loci, photoperiod- responsive floral repressors discovered through classic heritability studies. However, the identities of the genes underlying these loci have remained largely unknown. The elucidation of these genes allows for accelerated marker-assisted breeding programs and contributes to the understanding of flowering time in short day plants. Thus, in these studies, two Maturity Loci were identified using a map-based cloning approach, and alleles of each were sequenced in the germplasm. Expression analysis of individual genes by qRT-PCR and the transcriptome by RNAseq was utilized to characterize their response to photoperiod. Maturity Locus 1 (Ma1), the most effective of the loci, was identified as PSEUDORESPONSE REGULATOR 37, a component of the circadian clock. Sequence analysis revealed an allelic series at this locus, each conferring photoperiod insensitivity to varying degrees. It was demonstrated that the expression of this gene is regulated by the circadian clock, yet also highly dependent on light. Moreover, PRR37 was found to up-regulate floral repressors while down-regulating activators, providing a mechanism of flowering control consistent with the external coincidence model. Maturity Locus 6 (Ma6) also generated interest through its genetic interaction with Ma1, and was identified as Grain Yield, Plant Height and Heading Date 7 (Ghd7). Sequence analysis of Ghd7 revealed several severe mutations and these were traced through several Milo maturity standards, sweet and bioenergy varieties, as well as the pedigree of lines used heavily in the conversion of tropical sorghum to early flowering types. The expression of Ghd7 mirrors that observed for PRR37 and is also regulated by both light and the circadian clock. PRR37 and Ghd7 together confer greater repression of floral activators than either alone, but do so independently via pathways that converge on the same downstream "florigen". Thus in sorghum varieties with functional alleles of both, floral initiation is delayed indefinitely in long day photoperiods. The identification of these two genes provides a novel perspective on flowering in short day plants, while also accelerating breeding efforts that ultimately result in improved sorghum varieties for food, forage, and biofuels.

Low dropout regulators (LDOs) are important components for power management in modern integrated circuits. With the continued scaling down of power supply voltage, digital LDOs have become a more attractive design choice since they avoid the difficulty of designing high-gain amplifiers with low voltage. This thesis investigates techniques for both modeling and enhancement of digital LDO transient response. It discusses the importance of the resistance in the output stage of an LDO, and proposes a simulation model for examining LDO transient response. In addition, the thesis studies circuit techniques to improve LDO transient response. Different LDO circuits are implemented and compared in this study.

Made available in DSpace on 2014-06-11T19:26:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-24Bitstream added on 2014-06-13T20:34:24Z : No. of bitstreams: 1 takata_whs_me_botfca.pdf: 422211 bytes, checksum: 5af12fb97f188348230baf5f4a2c8a89 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O mercado de frutas exóticas no Brasil tem ganhado prestígio e o cultivo da pitaya apresenta-se promissor. Porém, o seu ciclo é limitado ao longo do ano, principalmente, pela influência do fotoperíodo no seu florescimento. A utilização de regulador vegetal, sobretudo a giberelina (GA), pode substituir a necessidade de dias longos. Nesse sentido se estudou diferentes épocas de aplicação e várias concentrações de GA3 no período não indutivo com o objetivo de induzir e antecipar o florescimento. O delineamento experimental utilizado foi blocos ao acaso em esquema fatorial 3x5, sendo três épocas de aplicação e cinco concentrações do regulador vegetal. As épocas de aplicação iniciaram em maio, junho e julho, sendo realizadas três aplicações a cada 30 dias. As concentrações estudadas foram 0, 100, 200, 300 e 400 mg L-1 de GA3. A época de aplicação de GA3 não influenciou em nenhuma das características estudadas, por outro lado o fator concentração, apesar de não ter antecipado o florescimento, proporcionou aumento na fixação de frutos, número de frutos, massa média de frutos e produtividade. Com base nos resultados obtidos é possível concluir que a aplicação de GA3 foi benéfica às características agronômicas da pitaya / The exotic fruit market in Brazil has gained prestige and cultivation of pitaya presents promising. But the cycle is limited throughout the year, and its flowering by photoperiod. The use of plant growth regulator, especially gibberellins, can replace the need for long days, in this sense, we studied different application periods and some concentrations of GA in non-inductive period in order to anticipate flowering. The experimental design was randomized blocks in factorial scheme 3x5, being three times of application and five concentrations of the GA3. The application periods began in May, June and July, and three times application, one every 30 days. The concentrations studied were 0, 100, 200, 300 and 400 mg L-1 GA3 application timing did not influence any of the traits on the other hand the concentration factor, despite not having anticipated the flowering could provide increased fruit set, fruit number, mean fruit mass and productivity. Based on the results, we concluded that the GA3 application was beneficial to the agronomic characteristics of pitaya

Made available in DSpace on 2014-06-11T19:26:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-28Bitstream added on 2014-06-13T20:34:28Z : No. of bitstreams: 1 vieira_mrs_me_botfca.pdf: 934932 bytes, checksum: 0d4804d6d955e5d2dde939bfc6d6770c (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A produção de flores de corte constitui uma atividade promissora, cuja comercialização exige técnicas de conservação que contribuem em manter a qualidade floral pós-colheita. A giberelina é um regulador vegetal que apresenta grande eficiência no crescimento, na indução de florescimento, na brotação, pode retardar a senescência, entre outros. Assim, o objetivo deste trabalho foi avaliar o efeito de baixas concentrações de ácido giberélico (GA3) aplicado a campo no crescimento da flor e qualidade pós-colheita de crisântemo cv. ‘Faroe’. As plantas foram pulverizadas aos 28 (vinte e oito) dias após o transplantio das mudas e a colheita programada com 95% das lígulas expandidas. Após a colheita, foram medidos os parâmetros: altura e diâmetro da haste, diâmetro da flor, comprimento da lígula, número de flores e tempo de reação (indução ao florescimento). Após a avaliação, as hastes foram armazenadas em câmara fria a temperatura de 10 °C e UR 95% durante 48 horas e levadas à temperatura ambiente. Após o periodo de armazenamento em câmara fria, foram comparadas com as hastes mantidas em temperatura ambiente e submetidas às seguintes análises: avaliação da senescência floral (escala de notas), consumo da solução do recipiente e medida do pH, ambas em intervalos de dois dias. A qualidade das hastes foi acompanhada pelas as análises bioquímicas (protéinas totais, carboidratos totais solúveis, atividade da peroxidase e poliaminas livres) no intervalo de quatro dias durante o tempo de vida de vaso. Apenas uma única aplicação de GA3 não teve interferência nas características fenotípicas em plantas de crisântemo cv ‘Faroe’, pelo menos em baixas concentrações, assim como não promoveram incremento na qualidade pós-colheita das flores. Não foi observado melhoria na qualidade das flores armazenadas... / The production of cut flowers is a promising commercial activity and its business demands conservation techniques that contribute to keep the post-harvested flower quality. Gibberellin is a growth regulator that is very efficient in the growth, flowering induction, budding, senescence delay, etc. Thus, the aim of this paper was to evaluate the effect of low concentrations of gibberellic acid (GA3) applied under field conditions on flower growth and post-harvest quality of chrysanthemums cv. ‘Faroe’. Application was carried out at 28 days after seedling transplanting and harvest was scheduled when 95% of ligulas were expanded. The following parameters were measured after harvest: stem height and diameter, flower diameter, ligula length, number of flowers and reaction time (flowering induction). After evaluation, the stems were stored in a cold chamber at 10° C and relative humidity of 95% for 48 hours and then taken to room temperature. Later they were compared to the stems kept at room temperature and submitted to the following analyses: flower senescence evaluation (score scale), solution consume, pH measurement, both at 2-day intervals. Stem quality was evaluated through biochemical analysis (total proteins, total soluble carbohydrates, peroxidase activity and free polyamines) at four-day intervals during the vase life. A single low concentration GA3 application has not interfered on phenotypic characteristics of chrysanthemum cv. ‘Faroe’ plants neither has improved post-harvested flower quality. There was not quality improvement of flowers stored in cold chamber after stem exposure to room temperature and flower senescence evaluation. In both treatments, stems presented a higher solution consume and pH varied during the vase life. Stems kept at room temperature showed great decreases in total protein content as well as in total soluble carbohydrate content in leaves and flowers of chrysanthemum cv. Faroe. There was an increase ...

Made available in DSpace on 2014-06-11T19:33:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-02-18Bitstream added on 2014-06-13T19:44:33Z : No. of bitstreams: 1 justi_mm_dr_jabo.pdf: 497881 bytes, checksum: 84f3db860aba3b676cb265a4612b41d8 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Com o objetivo de avaliar o efeito de doses de cloreto de mepiquat em cultivares de algodão herbáceo, foi conduzido um experimento no ano agrícola de 2002/2003, na Fazenda de Ensino e Pesquisa da FEIS/UNESP, localizada no município de Selvíria (MS). O delineamento experimental utilizado foi o de blocos ao acaso, com parcelas subdivididas, e quatro repetições. Nas parcelas foram estudados quatro cultivares de algodão (Coodetec 401, IAC 24, DeltaOpal e Deltapine Acala 90) e nas subparcelas, três doses de cloreto de mepiquat (0,0; 50,0 e 100,0 g i.a.ha-1). As parcelas experimentais constituíram-se de seis linhas com 10 m de comprimento e 0,90 m de espaçamento entrelinhas, sendo consideradas úteis as quatro linhas centrais. Foram determinados, em dez plantas de cada parcela, a altura das plantas e o diâmetro do caule. O número de nós no caule, número de ramos e de capulhos por planta foi obtido em cinco plantas amostradas de cada parcela. A produção de algodão em caroço foi determinada através da colheita dos capulhos em quatro metros de cada uma das duas linhas centrais. Amostras de 20 capulhos de cada parcela foram utilizadas para a obtenção da massa média de um capulho, massa de 100 sementes, porcentagem de fibra e características tecnológicas da fibra. A análise de crescimento foi feita determinando-se, a cada 14 dias, a área foliar e a massa seca acumulada nos diferentes órgãos da planta. A partir desses dados foram calculados a área foliar total, razão de área foliar, área foliar específica, razão de massa de folhas, taxa de crescimento relativo e taxa assimilatória líquida. Considerando-se 100% a massa seca total, determinou-se a distribuição em porcentagem da massa seca entre as diferentes estruturas da planta... / The experiment was conducted with the objective of evaluating the effect of doses of mepiquat chloride in cotton cultivars in the agricultural year of 2002/2003, at Teaching and Research Farm of FEIS/UNESP, located in Selvíria, MS, Brazil. The experimental design was complete blocks in split-plot arrangement and four replications. In the plots four cotton cultivars (Coodetec 401, IAC 24, DeltaOpal and Deltapine Acala 90) were studied and in the subplots, three doses of mepiquat chloride (0,0; 50,0 and 100,0 g i.a.ha-1). The experimental plots had six rows with 10 m of length and 0,90 m between rows, being considered useful the central four rows. The height of the plants and the diameter of the stem were measured in ten plants in each plot. The number of nodes in the stem, number of branches and of fruits per plant were obtained in five plants collected from each plot. The cotton yield was determined through the harvested fruits of the two central rows. Samples of 20 fruits of each plot were used to obtain the average mass of one fruit, mass of 100 seeds, fiber percentage and technological characteristics of the fiber. The growth analysis was performed by determining, every 14 days, the leaf area and the dry mass accumulated in the different organs of the plant. From those data, total leaf area, leaf area ratio, specific leaf area, ratio of leaf mass, relative growth rate and net assimilation rate, were calculated. Considering the total dry mass as 100%, the distribution, in percentage, of the dry mass among the different structures of the plant was determined. The obtained results allowed to conclude that 50,0 g i.a.ha-1 of mepiquat chloride caused minor height of the plants in the Coodetec 401, DeltaOpal and Deltapine Acala 90 cultivars while, for 24 IAC the dose of 100,0 g i.a.ha-1 was the best... (Complete abstract, click eletronic address below)