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System Interconnection Design Trade-offs in Three-Dimensional (3-D) Integrated CircuitsWeerasekera, Roshan January 2008 (has links)
Continued technology scaling together with the integration of disparate technologies in a single chip means that device performance continues to outstrip interconnect and packaging capabilities, and hence there exist many difficult engineering challenges, most notably in power management, noise isolation, and intra and inter-chip communication. Significant research effort spanning many decades has been expended on traditional VLSI integration technologies, encompassing process, circuit and architectural issues to tackle these problems. Recently however, three- dimensional (3-D) integration has emerged as a leading contender in the challenge to meet performance, heterogeneous integration, cost, and size demands through this decade and beyond. Through silicon via (TSV) based 3-D wafer-level integration is an emerging vertical interconnect methodology that is used to route the signal and power supply links through all chips in the stack vertically. Delay and signal integrity (SI) calculation for signal propagation through TSVs is a critical analysis step in the physical design of such systems. In order to reduce design time and mirror well established practices, it is desirable to carry this out in two stages, with the physical structures being modelled by parasitic parameters in equivalent circuits, and subsequent analysis of the equivalent circuits for the desired metric. This thesis addresses both these issues. Parasitic parameter extraction is carried out using a field solver to explore trends in typical technologies to gain an insight into the variation of resistive, capacitive and inductive parasitics including coupling effects. A set of novel closed-form equations are proposed for TSV parasitics in terms of physical dimensions and material properties, allowing the electrical modelling of TSV bundles without the need for computationally expensive field-solvers. Suitable equivalent circuits including capacitive and inductive coupling are derived, and comparisons with field solver provided values are used to show the accuracy of the proposed parasitic parameter models for the purpose of performance and SI analysis. The deep submicron era saw the interconnection delay rather than the gate delay become the major bottleneck in modern digital design. The nature of this problem in 3-D circuits is studied in detail in this thesis. The ubiquitous technique of repeater insertion for reducing propagation delay and signal degradation is examined for TSVs, and suitable strategies and analysis techniques are proposed. Further, a minimal power smart repeater suitable for global on-chip interconnects, which has the potential to reduce power consumption by as much as 20% with respect to a traditional inverter is proposed. A modeling and analysis methodology is also proposed, that makes the smart repeater easier to amalgamate in CAD flows at different levels of hierarchy from initial signal planning to detailed place and route when compared to alternatives proposed in the literature. Finally, the topic of system-level performance estimation for massively integrated systems is discussed. As designers are presented with an extra spatial dimension in 3-D integration, the complexity of the layout and the architectural trade-offs also increase. Therefore, to obtain a true improvement in performance, a very careful analysis using detailed models at different hierarchical levels is crucial. This thesis presents a cohesive analysis of the technological, cost, and performance trade-offs for digital and mixed-mode systems, outlining the choices available at different points in the design and their ramifications / QC 20100916
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Developing a lean enablers training program using virtual reality (VR) systemKayumi, Walid January 2013 (has links)
Training plays a major role in improving work within organisations by ensuring that the appropriate level of knowledge and skills are shared among personnel. It moulds the thinking process and leads to quality performance. However, training which includes a practical aspect usually targets a specific type of trainee and can limit the learning of an individual coming from a different background than that taken into consideration when the training programme was originally developed. This research focuses on training, and attempts to develop a program using a virtual reality (VR) system as a platform to create a simulated working environment which has the flexibility to train staff members of an organisation, who may come from a variety of different professional backgrounds, in the concept of the lean enablers. The main concern of this research is the adaptation of lean training for a virtual environment. Existing training methods have been analysed, along with the various ways in which they can be implemented, and these have been used in this research as a starting point from which to construct the virtual work environment. Through the research, a method has been developed to set up and run a training session using a virtual reality (VR) system by generating a structure to design the modelling elements that compose the virtual workplace, as well as establishing a method so that a trainee can navigate the simulated environment and perform tasks. A program to collect the performance measures and visualise the results has also been developed, with the aim of enabling the evaluation of a simulation run by assessors/trainers. This research covers new ground in providing a simulated working environment, which can suit any trainee’s professional background, to facilitate learning about the lean enablers. It offers the capacity of establishing a simulated work environment which can represent the trainee’s workplace and provide the necessary practical experience in order to grasp the concept taught through the training program. Additionally it offers the capacity for assessors/trainers to observe the performance measures and the trainee’s behaviour, simultaneously, while undertaking a simulation run. These combinations of information can be complementary and enable assessors/trainers in providing the best feedback while improving the learning curve of a trainee. Although training programmes in organisations have provided a number of improvements in completing work with high efficiency and minimum waste, the outcomes collected in this research demonstrate that their benefits can be pushed further in terms of providing a training method which can be accessible to a large variety of sectors.
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Expressão gênica do receptor de IGF-1 em células da granulosa luteinizadas de mulheres com síndrome dos ovários policísticos (SOP), não obesas, com sensibilidade à insulina normal, tratadas e não tratadas com metformina / Gene expression of the IGF-1 receptor in luteinized granulosa cells from non-obese women with polycystic ovarian syndrome (PCOS) and with normal insulin sensitivity, treated or not withmetforminSantana, Laura Ferreira 09 August 2007 (has links)
OBJETIVO: avaliação da expressão gênicado receptor do fator de crescimento semelhante à insulina de (Insulin-Like Growth Factor- IGF) 1 em células da granulosa luteinizadas do cumulusde mulheres não obesas, com sensibilidade à insulina normal, com síndrome dos ovários policísticos (SOP) tratadas e não tratadas com metformina. MODELO DO ESTUDO: prospectivo, longitudinal, randomizado. PACIENTES E MÉTODOS: avaliamos 12 mulheres com ciclosovulatórios, 9 mulheres com SOP e 8 mulheres com SOP e tratadas com metformina, ao menos 8 semanas na dose de 1.700 mg/dia. Todos os grupos foram similares com relação ao peso, ao índice de massa corporal (IMC), à circunferência da cintura e com sensibilidade à insulina normal. Todas as mulheres foram submetidas à estimulação ovariana controlada com uso de agonista de GnRH em protocolo longo e gonadotrofinas para ciclos de FIV/ICSI. As células da granulosa do cumulusforam obtidas por microdissecção dos cinco maiores folículos pré-ovulatórios. A expressão gênica do receptor de IGF-1 foi determinada com técnica da Reação da Polimerase em Cadeia a partir da Transcrição Reversa (Reverse transcriptase - Polymerase Chain ReactionRT-PCR) emiquantitativa. Foram avaliadas as concentrações séricas e foliculares de estradiol, progesterona, testosterona, hormônio folículo estimulante (Follicle-Stimulating Hormone- FSH), hormônio luteinizante (Luteinizing Hormone - LH), Sex Hormone-Binding Globulin(SHBG), glicose, insulina e IGF-1. Para análise estatística, foram utilizados os testes: ANOVA, Newman-Keuls, coeficiente de Pearsone regressão linear múltipla, sendo considerado nível de significância de 5%. RESULTADOS: não foram observadas diferenças com relação à expressão gênica do receptor de IGF-1 nos três grupos analisados (P>0,05). O número de oócitos (20,4 vs. 13,1 vs.11,5, P= 0,009), os níveis séricos de estradiol (1.896,00 pcg/mL vs. 985,20 pcg/mL vs.908,10 pcg/mL,P = 0,03) e testosterona (1,43 ng/mL vs.0,89 ng/mL vs. 0,82 ng/mL pcg/mL,P = 0,02) foram maiores no grupo de mulheres com SOP não tratadas com metformina em comparação com as mulheres com ciclos ovulatórios e tratadas com metformina, respectivamente. As mulheres com ciclos ovulatórios (50.710±42.520 ng/mL) apresentaram maiores concentrações foliculares de progesterona quando comparados com as mulheres com SOP tratadas (13.660±5.212 ng/mL) e não tratadas com metformina (17.680±6.644 ng/mL) (P=0,01). Na avaliação da regressão múltipla, a testosterona sérica não sofreu influência da expressão gênica do receptor de IGF-1 ou do IMC. CONCLUSÕES: as altas concentrações séricas de estradiol e testosterona, maior número de oócitos no grupo de mulheres com SOP não tratadas com metformina nos levam a concluir que mulheres com SOP provavelmente têm uma maior sensibilidade à estimulação da esteroidogênese ovariana quando comparadas com mulheres sem essa doença, embora não tenhasido encontrada diferença na expressão do receptor de IGF-1 nos trêsgrupos analisados. A similaridade dos resultados deste estudo entre mulheres com SOP tratadas com metformina e com ciclos ovulatórios nos levam a \"hipotetizar\" que um dos possíveis mecanismos de ação da metformina no sistema IGF-1 nas células da granulosa do cumulus poderia ser por mecanismos pós-receptores. / OBJECTIVE: evaluation of the gene expression of the IGF-I receptor in luteinized cumulus granulosa cells from non-obese women with normal insulin sensitivity and with polycystic ovarian syndrome (PCOS)treated or nor with metformin. STUDY MODEL: prospective,longitudinal, randomized. PATIENTS AND METHODS: we evaluated 12 women withovulatory cycles and 9 women with PCOS who had been treated for at least 8 weeks with a metformin dose of 1700 mg/day. All groups were similar interms of weight, body mass index (BMI), and waist circumference and all had normal insulin sensitivity. All women were submitted to controlled ovarian stimulation with a GnRH agonist in a long protocol and with gonadotropins for IVF/ICSI cycles. Cumulus granulosa cells were obtained by microdissection of the five largest pre-ovulatory follicles. Gene expression of the IGF-1 receptor was determined by semiquantitative RT-PCR. Serum and follicular concentrations of estradiol, progesterone, testosterone, FSH, LH, insulin, SHBG, and IGF-1 were determined. Data were analyzed statistically by ANOVA and by the Newman-Keuls test and the Pearson coefficient and linear multiple regression were calculated, with the level of significance set at 5%. RESULTS: no difference in geneexpression of the IGF-I receptor were observed between the three groups studied (P>0.05). The number of oocytes (20.4 vs. 13.1 vs. 11.5, P= 0.009) and the serum levels of estradiol (1,896.00 pcg/mL vs. 985.20 pcg/mL vs.908.10 pcg/mL,P = 0.03) and testosterone (1.43 ng/mL vs.0.89 ng/mL vs. 0.82 ng/mL pcg/mL,P = 0.02) were higher in the group of women with PCOS not treated with metformin than in women with ovulatory cycles and in women treated with metformin, respectively. The women with ovulatory cycles (50.710±42.520 ng/mL) presented higher follicular concentrations of progesterone compared with women with PCOS treated (13.660±5.212 ng/mL) or not with metformin (17.680±6.644 ng/mL) (P=0.01). Multiple regression revealed that serum testosterone was not affected by the gene expression of the IGF-1 receptor or by BMI. CONCLUSIONS: the high serum concentrations of estradiol and testosterone and the larger number of oocytes in the group ofwomen with PCOS not treated with metformin lead us to conclude that women with PCOS probably have greater sensitivity to stimulation ofovarian steroidogenesis than women without the disease, although no difference was detected in the expression of the IGF-I receptor between the three groups studied. The similarity ofthe present results for the women with PCOS treated with metformin and for the women with ovulatory cycles leads us to hypothesize that one of the possible mechanisms of action of metformin on the IGF-1 system in cumulus granulosa cells may be of the post-receptor type.
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ANÁLISE DOS CRITÉRIOS CLÍNICOS DE DIAGNÓSTICO DA SÍNDROME DOS OVÁRIOS POLICÍSTICOS SEGUNDO OS CONSENSOS / ANALYSIS OF THE CLINICAL CRITERIA OF DIAGNOSTIC OF POLYCYSTIC OVARY SYNDROME ACCORDING TO CONSENSUSFreire, Glaúcia Iraúna de Melo 18 June 2012 (has links)
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Previous issue date: 2012-06-18 / Polycystic Ovary Syndrome (PCOS) is diagnosed by consensus of the National Institute of Health (NIH- USA, 1990), Rotterdam (Netherlands, 2003) and Androgen Excess Syndrome - PCOS (AES-PCOS, 2006). It is important to recognize the clinical characteristics of PCOS patients in Maranhão to submit a profile Objectives: To evaluate the prevalence of the PCOS according to the current guidelines for PCOS and Maranhão women, s profile. Methodology: A cross sectional sample of 102 women diagnosed with PCOS, attending at the gynecology clinic of the Materno Infantil Hospital in São Luís -MA. The clinical classification was analyzed by applying the inclusion and exclusion criteria of the NIH, and AES- PCOS. Data were tabulated and analyzed using Microsoft Office Excel 2007 by graphs and frequency tables. Results: Most of the patients were between 20 and 25 years old with 41,2%(n= 42); brown 50%(n= 51), single 52,9%(n=54); 11years of school,44,1%(n= 45) and menarche between 12 and 14 years old with 34,3% (n= 50). They were within normal anthropometrically exception to the waist circumference where the abnormality was more common in 65, 8 %(n= 52). Clinical hyperandrogenism was observed in 51 %( n= 52) of patients, predominance of hirsutism with 32,3% (n= 33) and the laboratorial with 13,7%(n= 14). Ovulatory dysfunctional was the predominant complaint in 90, 2% ( n= 92), highlights for oligomenorrhea with 61,8%(n= 63). As for the phenotypes, there was a predominance of ovary dysfunction and policistose ovarian at 48% (n= 49) (ROTTERDAM), hyperandrogenism and dysfunction was more frequent phenotypes with 81, 1% (n= 43) (NIH) and 42, 1% (n= 43) (AES-PCOS). Conclusion: The most common feature of PCOS was hyperandrogenism and the most prevalent clinical expression was found by applying the Rotterdam criteria. / A síndrome dos ovários policísticos (SOP) é diagnosticada pelos consensos do Instituo Nacional de Saúde (National Institute of Health- NIH/ EUA, 1990), de Rotterdam (Holanda, 2003) e da Sociedade de Excesso de Androgênios e Síndrome dos Ovários Policísticos (AES- PCOS, 2006 É importante reconhecer as características clinicas da SOP nas pacientes maranhenses para a apresentação de um perfil. Objetivos: Avaliar a prevalência da SOP de acordo com os consensos vigentes para SOP e Conhecer o perfil da SOP nas mulheres maranhenses. Metodologia: Estudo transversal, com amostra de 102 mulheres com diagnóstico clínico de SOP, atendidas no ambulatório de ginecologia especializada do Hospital Universitário Materno Infantil em São Luís MA. A classificação clínica foi estabelecida pelos consensos de NIH, e AES- PCOS. Os dados foram tabulados e analisados no programa Microsoft Office Excel 2007 por meio de gráficos e tabelas de frequência. Resultados: A maioria das pacientes tinha entre 20 e 25 anos (41,2% - n=42),parda 50%(n=51), solteiras 52,9%(n=54), com ensino médio 44,1%(n=45) e menarca entre 12 e 14 anos com 34,3% (n=50), aumento de colesterol total em 22,5% (n=23), HDL em 23,5 %( n=24), Triglicérides em 9,8%( n=10), glicemia aumentada em 5,8%( n=6),com hipertensão arterial sistólica, 5,8%( n=6) e diastólica, 15,7%( n=16); índice de Massa Corpórea estava maior que 30 kg/m² em 25,5%(n=26); com 51%(52) destas mulheres com a cintura abdominal acima da normalidade(88 cm). O hiperandrogenismo foi evidente em 68,6%(70) com hirsutismo em 54,3% (32) e a disfunção ovulatória ocorreu em 90,2% (92) e ovários policísticos em 78,4% (80) das pacientes.De acordo com os consensos,os aspectos disfunção ovulatória, policistose e hiperandrogenismo com 39,2% (40) pelo consenso de Rotterdam. Nos critérios do AES, foram 58,8%(60) com hiperandrogenismo e disfunção ovulatória e o hiperandrogenismo e a disfunção ovulatória pelo NIH com 58,8% (60). Conclusão: Hiperandrogenismo, disfunção ovulatória e ovários policísticos foram mais frequentes e a queixa mais comum foi a oligomenorréia. E o hiperandrogenismo, foi a expressão clínica mais prevalente independente do critério adotado.
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Design of Baluns and Low Noise Amplifiers in Integrated Mixed-Signal Organic SubstratesGovind, Vinu 19 July 2005 (has links)
The integration of mixed-signal systems has long been a problem in the semiconductor industry. CMOS System-on-Chip (SOC), the traditional means for integration, fails mixed-signal systems on two fronts; the lack of on-chip passives with high quality (Q) factors inhibits the design of completely integrated wireless circuits, and the noise coupling from digital to analog circuitry through the conductive silicon substrate degrades the performance of the analog circuits. Advancements in semiconductor packaging have resulted in a second option for integration, the System-On-Package (SOP) approach. Unlike SOC where the package exists just for the thermal and mechanical protection of the ICs, SOP provides for an increase in the functionality of the IC package by supporting multiple chips and embedded passives. However, integration at the package level also comes with its set of hurdles, with significant research required in areas like design of circuits using embedded passives and isolation of noise between analog and digital sub-systems.
A novel multiband balun topology has been developed, providing concurrent operation at multiple frequency bands. The design of compact wideband baluns has been proposed as an extension of this theory. As proof-of-concept devices, both singleband and wideband baluns have been fabricated on Liquid Crystalline Polymer (LCP) based organic substrates. A novel passive-Q based optimization methodology has been developed for chip-package co-design of CMOS Low Noise Amplifiers (LNA). To implement these LNAs in a mixed-signal environment, a novel Electromagnetic Band Gap (EBG) based isolation scheme has also been employed.
The key contributions of this work are thus the development of novel RF circuit topologies utilizing embedded passives, and an advancement in the understanding and suppression of signal coupling mechanisms in mixed-signal SOP-based systems. The former will result in compact and highly integrated solutions for RF front-ends, while the latter is expected to have a significant impact in the integration of these communication devices with high performance computing.
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RF MEMS Switches with Novel Materials and Micromachining Techniques for SOC/SOP RF Front EndsWang, Guoan 03 August 2006 (has links)
This dissertation deals with the development of RF MEMS switches with novel materials and micromachining techniques for the RF and microwave applications. To enable the integration of RF and microwave components on CMOS grade silicon, finite ground coplanar waveguide transmission line on CMOS grade silicon wafer were first studied using micromachining techniques. In addition, several RF MEMS capacitive switches were developed with novel materials. A novel approach for fabricating low cost capacitive RF MEMS switches using directly photo-definable high dielectric constant metal oxides was developed, these switches exhibited significantly higher isolation and load capacitances as compared to comparable switches fabricated using a simple silicon nitride dielectric. The second RF MEMS switch developed is on a low cost, flexible liquid crystal polymer (LCP) substrate. Its very low water absorption (0.04%), low dielectric loss and multi-layer circuit capability make it very appealing for RF Systems-On-a-Package (SOP). Also, a tunable RF MEMS switch on a sapphire substrate with BST as dielectric material was developed, the BST has a very high dielectric constant (>300) making it very appealing for RF MEMS capacitive switches. The tunable dielectric constant of BST provides a possibility of making linearly tunable MEMS capacitor-switches. For the first time a capacitive tunable RF MEMS switch with a BST dielectric and its characterization and properties up to 40 GHz was presented. Dielectric charging is the main reliability issue for MEMS switch, temperature study of dielectric polarization effect of RF MEMS was investigated in this dissertation. Finally, integration of two reconfigurable RF circuits with RF MEMS switches were discussed, the first one is a reconfigurable dual frequency (14GHz and 35 GHz) antenna with double polarization using RF MEMS switches on a multi-layer LCP substrate; and the second one is a center frequency and bandwidth tunable filter with BST capacitors and RF MEMS switches on sapphire substrate.
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Development of microwave/millimeter-wave antennas and passive components on multilayer liquid crystal polymer (LCP) technologyBairavasubramanian, Ramanan 05 April 2007 (has links)
The investigation of liquid crystal polymer (LCP) technology to function as a low-cost next-generation organic platform for designs up to millimeter-wave frequencies has been performed.
Prior to this research, the electrical performance of LCP had been characterized only with the implementation of standard transmission lines and resonators. In this research, a wide
variety of passive functions have been developed on LCP technology and characterized for the first time. Specifically, we present the development of patch antenna arrays for remote sensing applications, the performance of compact low-pass and band-pass filters up to millimeter-wave frequencies, and the integration of passive elements for X-band and V-band transceiver systems.
First, dual-frequency/dual-polarization antenna arrays have been developed on multilayer LCP technology and have been integrated with micro-electro-mechanical-system (MEMS) switches to achieve real-time polarization reconfigurability. These arrays are conformal, efficient and have all the features desirable for
applications that require space deployment.
Second, a wide variety of filters with different physical and functional characteristics have been implemented on both single and multilayer LCP technology. These filters can be classified
based on the filter type (low-pass/band-pass), the resonators used (single-mode/dual-mode), the response characteristics (symmetric/asymmetric), and the structure of the filter (modular/non-modular).
Last, examples of integrated modules for use in transceiver systems are presented. This part of the research involves the development of duplexers, radiating elements, as well as their
integration. The duplexers themselves are realized by integrating a set of band-pass filters and matching networks. The characterization of the individual components, and of the integrated system are included.
This research has resulted in a thorough understanding of LCP's electrical performance and its multilayer lamination capabilities pertaining to its functioning as a material platform for
integrated microwave systems. Novel passive prototypes that can take advantage of such multilayer capabilities have been developed.
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Highly Integrated Three Dimensional Millimeter-Wave Passive Front-End Architectures Using System-on-Package (SOP) Technologies for Broadband Telecommunications and Multimedia/Sensing ApplicationsLee, Jong-Hoon 05 July 2007 (has links)
The objective of the proposed research is to present a compact system-on-package (SOP)-based passive front-end solution for millimeter-wave wireless communication/sensor applications, that consists of fully integrated three dimensional (3D) cavity filters/duplexers and antenna. The presented concept is applied to the design, fabrication and testing of V-band transceiver front-end modules using multilayer low temperature co-fired (LTCC) technology.
The millimeter-wave front-end module is the foundation of 60 GHz (V-band) wireless systems for short-range multimedia applications, such as high-speed internet access, video streaming and content download. Its integration poses stringent challenges in terms of high performance, large number of embedded passive components, low power consumption, low interference between integrated components and compactness. To overcome these major challenges, a high level of integration of embedded passive functions using low-cost and high-performance materials that can be laminated in 3D, such as the multilayer LTCC, is significantly critical in the module-level design.
In this work, various compact and high-performance passive building blocks have been developed in both microstrip and cavity configurations and their integration, enabling a complete passives integration solution for 3D low-cost wireless millimeter-wave front-end modules. It is worthy to note that most of the designs implemented comes away with novel ideas and is presented as the first extensive state-of-art components, entirely validated by measured data at 60 GHz bands.
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Design, Modeling, and Characterization of Embedded Passives and Interconnects in Inhomogeneous Liquid Crystalline Polymer (LCP) SubstratesYun, Wansuk 13 November 2007 (has links)
The goal of the research in this dissertation is to design and characterize embedded passive components, interconnects, and circuits in inhomogeneous, multi-layer liquid crystalline polymer (LCP) substrates.
The attenuation properties of inhomogeneous multi-layer LCP substrates were extracted up to 40 GHz. This is the first result for an inhomogeneous LCP stack-up that has been reported. The characterization results show excellent loss characteristics, much better than FR-4-based technology, and they are similar to LTCC and homogeneous LCP-based technology.
A two-port characterization method based on measurements of multiple arrays of vias is proposed. The method overcomes the drawbacks of the one-port and other two-port characterizations. Model-to-hardware correlation was verified using multi-layer model in Agilent ADS and measurement-based via model using arrays of the vias. The resulting correlations show that this method can be readily applied to other vertical interconnect structures besides via structures.
Comprehensive characterizations have been conducted for the efficient 3D integration of high-Q passives using a balanced LCP substrate. At two different locations from three different large M-LCP panels, 76 inductors and 16 3D capacitors were designed and measured. The parameters for the measurement-based inductor model were extracted from the measured results. The results validate the large panel process of the M-LCP substrate. To reduce the lateral size, multi-layer 3D capacitors were designed. The designed 3D capacitors with inductors can provide optimized solutions for more efficient RF front-end module integration. In addition, the parameters for the measurement-based capacitor model were extracted.
Various RF front-end modules have been designed and implemented using high-Q embedded passive components in inhomogeneous multi-layer LCP substrates. A C-band filter using lumped elements has been designed and measured. The lumped baluns were used to design a double balnced-mixer for 5 GHz WLAN application and a doubly double-balanced mixer for 1.78 GHz CDMA receiver miniaturization. Finally, to overcome the limitations of the lumped component circuits, a 30 GHz gap-coupled band-pass filter in inhomogeneous multi-layer LCP substrates, and the measured results using SOLT and TRL calibrations have been compared to the simulation results.
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Novel Nonvolatile Memory for System on Panel ApplicationsJian, Fu-yen 13 April 2010 (has links)
Recently, active matrix flat-panel displays are widely used in consumer electronic products. With increasing popularity of flat-panel displays, market competition becomes more intense and demands for high performance flat-panel displays are increasing. Low-temperature polysilicon (LTPS) with higher mobility, as well as drive current can integrate electric circuit, such as controllers and memory on glass substrate of display to achieve the purpose of system on panel (SOP). Thus, flat-panel displays can be more compact, while reducing reliability issues and lowering production costs.
In this dissertation, we studied the nonvolatile memory for system on panel applications and reducing cost of memory by increasing the memory density or reducing the processing steps. Therefore, we proposed several modes of operation in nonvolatile memory.
First, we use channel hot-electron (CHE) to inject electrons into the nitride layer that¡¦s above source or drain sides of SONOS thin film transistor (TFT). Thus, we can increase the memory density by storing two-bit state in a memory cell. In this study, the two-bit memory effect is clearly observed for devices with a shorter gate length after CHE programming; however, the two-bit memory effect is absent in devices with a longer gate length. The gate-length-dependent two-bit memory effect is related to the location of injected electrons in the nitride layer. When electrons are injected into the nitride layer above the channel, they can create an additional energy barrier in the channel thus increasing the threshold voltage of the device to perform the programming operations. However, if electrons are injected into the depletion region at the P-N junction between the drain and the channel, the energy barrier induced by electrons is not significant when exchanging the source and drain electrodes to measure the memory status, and the program effect is not as significant. When the channel length is shorten, the built-in potential between the source and the channel can be decreased, the energy barrier caused by programmed electrons can affect electrons in the channel and increase the threshold voltage. Therefore, the two-bit memory effect can be seen in devices with the shorter gate length after CHE programming.
Secondly, we stored charges in the body of the thin film transistor to make the conventional thin-film transistors become a non-volatile memory. This method does not need a floating gate or a tunneling oxide in the memory cell; therefore the memory cost can be reduced. In this study, we used trap-assisted band-to-band thermionic field emission enhanced by self-heating in TFT to produce electron-hole pairs. The hole will be separated by a vertical field under the gate and be injected into the body of TFT to complete the programming operation. The erasing operation is performed by applying a lateral electric field between the source/drain to remove holes in the body of TFT.
Thirdly, we proposed an edge-FN tunneling method to allow SONOS TFT possess not only a pixel switch but also a two-bit nonvolatile memory function in a display panel, thus causing the memory density to increase. In this study, we used a channel FN tunneling to program the SONOS TFT. Because the electric field in the gate-to-drain overlap region is larger than that in the channel region, it will cause a smoother electron injection into the nitride layer inside of the gate-to-drain overlap region, which also increases the gate-induced drain leakage (GIDL) current. The edge-FN tunneling method is used to erase electrons in the gate-to-drain overlap region, by doing so, the GIDL current has decreased. The memory status at the source/drain side is determined by the corresponding GIDL current of the SONOS TFT.
Fourthly, we stored electrons in the nitride layer at source, channel, and drain regions of SONOS TFT to make sure that TFT possess a three-bit memory effect in a unitary cell, which also allows the memory density to increase significantly. In this study, programming and erasing operations in the source/drain region are performed by channel hot-electron injection and edge-FN tunneling method, while that in the channel region are accomplished by channel FN tunneling. The memory status in the source/drain is determined by the corresponding GIDL current, while that in the channel region by threshold voltage of the device The memory density for the device operated by proposed method can be further increased.
In addition, if we store a number of N different types of electrons in those three regions mentioned above, there are N3 status can be stored in a memory cell. The memory density can beyond conventional multi-level-cell (MLC) flash memory. Two-bit memory effect per cell in a MLC flash memory can be achieved by storing four quantitative electrons in the floating gate of the memory device. If we store four quantitative electrons in the nitride layer at source, channel, and drain regions of SONOS TFT, we can obtain 64 memory states or 6-bit memory effect in a memory cell. Thus, the proposed concept is promising to storage the messages in a memory cell beyond four-bit.
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