Measurements, Models, Systems and Design

531 s.

Síntese Digital Direta

Os projetos tradicionais de sintetizadores de frequência de elevada largura de banda utilizam um circuito fechado de fase (PLL). Um sintetizador digital direto, ou na terminologia inglesa, Direct Digital Dynthesis (DDS) oferece muitas vantagens significativas sobre as abordagens PLL como, por exemplo, um tempo de estabilização rápido, resolução de frequência sub-Hertz, resposta de comutação de fase contínua e baixo ruído de fase. Embora o princípio do DDS seja conhecido há muitos anos, o DDS não desempenhou um papel dominante na geração de frequência de banda larga até recentemente. Os DDSs iniciais eram limitados a produzir frequências estreitamente espaçadas com pequena largura de banda, devido a limitações da lógica digital e das tecnologias de conversão D/A. As vantagens recentes nas tecnologias de circuitos integrados (CI) trouxeram um progresso notável nesta área. Ao programar um DDS, é possível adaptar as larguras de banda de canal, formatos de modulação, salto de frequência e taxas de dados. Este é um passo importante em direção a um “software-rádio” que pode ser usado em vários sistemas. Um DDS pode ser aplicado no modulador ou demodulador nos sistemas de comunicação. O objetivo desta pesquisa foi encontrar um frontend ideal para um transmissor, concentrando-se nas implementações de circuito do DDS, mas a pesquisa também inclui a interface para circuitos de banda base e aspetos de design de nível de sistema de sistemas de comunicação digital.Traditional high-bandwidth frequency synthesizer designs utilize a phase closed loop (PLL). A direct digital synthesizer, or in English terminology, Direct Digital Dynthesis (DDS) offers many significant advantages over PLL approaches such as a fast-settling time, sub-Hertz frequency resolution, continuous phase switching response and low phase noise. Although the principle of DDS has been known for many years, DDS has not played a dominant role in broadband frequency generation until recently. Early DDSs were limited to producing closely spaced frequencies with low bandwidth, due to limitations of digital logic and D/A conversion technologies. Recent advances in integrated circuit (IC) technologies have brought remarkable progress in this area. When programming a DDS, it is possible to adapt channel bandwidths, modulation formats, frequency hopping and data rates. This is an important step towards “radio software” that can be used on multiple systems. A DDS can be applied in the modulator or demodulator in the communication systems. The purpose of this research was to find an ideal frontend for a transmitter, focusing on the circuit implementations of DDS, but the research also includes the interface to baseband circuits and system-level design aspects of digital communication systems

Implementação em FPGA do transceiver FMCOMMS3 para o protocolo de comunicação DVBS2X

Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Faculdade UnB Gama, Engenharia Eletrônica, 2020.Esse trabalho apresenta um estudo detalhado da implementação em FPGAs (Field Programmable Gate Arrays) de um sistema operacional embarcado via PetaLinux desenvolvido para ser o front-end de um sistema de recepção para o protocolo de comunicação DVB-S2X integrado com o transceiver FMCOMMS3 em comparação com um DDC (Digital Down Converter) totalmente desenvolvido no hardware programável do FPGA. É também desenvolvido nesse documento a integração do DDC com o CFC (Cource Frequency Correction) conforme normatizado no padrão DVB-S2X. Por fim são feitas ponderações do desempenho entre o sistema front-end em SDR (Software Defined Radio) implementado através do PetaLinux e o circuito do DDC implementado em hardware e descrito em VHDL. Um dos componentes inerentes a qualquer padrão é o módulo de recepção do sinal, especificamente o DDC, para qual existem várias soluções implementadas tanto em hardware quanto para aplicações em SDR. A proposta central deste trabalho é desenvolver um sistema de recepção para a placa ZCU104 da empresa Xilinx integrada fisicamente com o transceiver FMCOMMS3 da empresa Analog Devices por meio do PetaLinux, em paralelo a um Digital Down converter em hardware integrado com o CFC. No caso do PetaLinux visa-se desenvolver um sistema operacional ainda não disponibilizado oficialmente pela empresa Analog Devices para o kit de desenvolvimento ZCU104. Observa-se que a empresa, até o presente momento, disponibiliza oficialmente o PetaLinux para a placa ZCU102, contudo, essa segunda é uma placa com um custo maior que a ZCU104 que possui entradas FMC que permitiria a mesma implementação a um custo menor. Em relação ao DDC visa-se explorar de forma intrínseca as especificidades do padrão DVBS2X, como largura de banda, Roll-off, taxa de bits e entre outras métricas se refletindo em um baixo custo de implementação explorando a quantidade de coeficientes dos filtros, formas de ondas esperadas e resolução do oscilador acarretando em uma redução efetiva do processamento ao longo de toda cadeia da down conversão sem perda de generalidade. A generalidade irá se manter pois todos os coeficientes, largura de banda, excursão de frequência são configurados diretamente na descrição do hardware ou usando scripts desenvolvidos como modelos de referência em software que geram os trechos da descrição em hardware. Adicionalmente todos os circuitos foram sintetizados e implementados no FPGA para uma taxa de amostragem de 100 MSPS e caracterizados em termos de precisão, recursos de hardware, latência, throughput e consumo de energia e então comparados com as soluções existentes. Os resultados experimentais mostram que o circuito projetado e integrado com o CFC é viável e eficiente para a recepção e sincronização do sinal conforme a norma DVB-S2X, além de consumir menos recursos e tempo de execução do que os encontrados na literatura.This paper presents a detailed study of the implementation in FPGAs ( textit Field Programmable Gate Arrays) of an embedded operating system via PetaLinux developed to be the textit front-end of a reception system for the communication protocol DVB- S2X integrated with the FMCOMMS3 transceiver compared to a DDC textit (Digital Down Converter) fully developed on the FPGA’s programmable hardware. It is also developed in this document the integration of the DDC with the CFC ( textit Cource Frequency Correction) as standardized in the DVB-S2X standard. Finally, performance considerations are made between the textit front-end system in SDR textit (Software Defined Radio) implemented through PetaLinux and the DDC circuit implemented in hardware and described in VHDL. One of the components inherent to any standard is the signal reception module, specifically the DDC, for which there are several solutions implemented both in hardware and for SDR applications. The main proposal of this work is to develop a reception system for the ZCU104 board from the company Xilinx physically integrated with the FMCOMMS3 transceiver from the company Analog devices through PetaLinux, in parallel a Digital Down converter in hardware integrated with the CFC. In the case of PetaLinux, the aim is to develop an operating system not yet officially made available by the company Analog devices for the ZCU104 development kit. It is observed that the company, until now, officially makes PetaLinux available for the ZCU102 board, however, this second one is a board with a higher cost than the ZCU104 that has FMC inputs that would allow the same implementation at a lower cost. Regarding DDC, the aim is to explore intrinsically the specifics of the DVB-S2X standard, such as bandwidth, textit Roll-off, bit rate and other metrics, reflecting a low cost of implementation exploring the amount filter taps, expected waveforms and oscillator resolution resulting in an effective reduction in processing along the entire down conversion chain without loss of generality. The generality will remain as all the coefficients, bandwidth, frequency excursion are configured directly in the hardware description or using scripts developed as reference models in software that generate the parts of the hardware description. Additionally, all circuits were synthesized and implemented in the FPGA for a sampling rate of 100 MSPS and characterized in terms of precision, hardware resources, latency, textit throughput and energy consumption and then compared with existing solutions. The experimental results show that the circuit designed and integrated with the CFC is feasible and efficient for the reception and synchronization of the signal according to the DVB-S2X standard, in addition to consuming less resources and execution time than those found in the literature

Bioimpedance measurement device for chronic wound healing monitoring

A chronic wound is loosely defined as a wound that fails to heal within a time period of a few months. Elderly bedridden people and people suffering from certain underlying medical conditions, such as vascular diseases and type 2 diabetes, are particularly prone to develop chronic wound. The group of people exposed is increasing in numbers. Treatment of a chronic ulceration is very costly and the monitoring of healing is often based on visual inspection by medical professionals. There exists a need for objective and non-intrusive method for assessment of chronic wound healing. In this Master of Science Thesis a prototype of a bioimpedance device for monitoring of chronic wound healing was designed, constructed and tested. The device works from an indicator basis and measures the changes in the tissue impedance. The direction of the change correlates with the change in the volume and in the conductivity of the tissue, consequently in the swelling around the inflamed wound. Decrease in extracellular fluid can be detected as increasing low frequency impedance. The device measures impedance at 5kHz and 100kHz frequency by using triangular excitation. The emphasis of the design was on the simplicity of the device to provide a possibility for downscaling in the future. Ultimately the device would be integrated on a patch type platform together with a drug delivery system. The test measurements with the bioimpedance device were fairly extensive. The measurements were performed with a purely resistive load and a 2R-1C circuit. For 5kHz excitation the results for both load circuits did show only a slight mean error with a fairly small standard deviation. For 100kHz excitation the results did show larger mean error with a small standard deviation. Small standard deviation points to a systematic error. However, the 100kHz results are somewhat controversial since the difference between mean error for the purely resistive load and for the 2R-1C is fairly large. Restricted in vivo measurements were also performed. The in-vivo measurements did show large error compared to the reference measurements. Due to the limited nature of the measurements solid conclusions from these measurements cannot be made. All in all, the test measurements indicate the potential of simplified design. The accuracy of the device can be increased remarkably with certain improvements made to the design

New dynamical process for analysis and phase control of the synthetic wavefront of a laser beam array

Des projets futuristes tels que la production d’énergie par fusion nucléaire, ou encore la navigation interstellaire par voiles solaires, requièrent l’utilisation d’une source de lumière de luminance extrême. Dans l’objectif d’augmenter la luminance de sources lasers, mes travaux de thèse ont porté sur la combinaison cohérente de réseaux de lasers. Ils ont conduit au développement d’un nouveau procédé de contrôle compact du front d’onde de synthèse formé par le réseau de faisceaux lasers. Ce procédé permet de sculpter à façon la figure intensimétrique du champ lointain et donc de contrôler la distribution angulaire d’énergie émise par le réseau de faisceaux lasers. Le procédé développé utilise un module convertisseur phase/amplitude intégrant un élément diffuseur. Une méthode de mesure de la matrice de transfert d’un système optique a été développée pour caractériser ce module convertisseur de champ. A tout instant, le front d’onde de synthèse est estimé par une boucle numérique de recouvrement de phase basée sur un algorithme à projections alternées. Ce calcul approché permet d’ajuster progressivement les relations de phases du réseau de faisceaux lasers jusqu’au jeu de phases arbitraire souhaité. Le procédé permet le contrôle d’un front d’onde de synthèse en moins de 10 corrections de phases, quasi-indépendamment du nombre de faisceaux lasers à contrôler. Il est robuste aux défauts environnementaux et indépendant du jeu de phases initiales. J’ai démontré la compacité du système étudié en analysant et contrôlant une pupille de synthèse de 4 cm de côté, constituée de 16 faisceaux, à l’aide d’un module d’analyse mesurant seulement 30 cm. J’ai également montré expérimentalement le contrôle des phases de réseaux de 16 à 100 faisceaux lasers avec des erreurs résiduelles valant respectivement λ/30 et λ/20 rms. Les capacités de cette méthode peuvent être étendues au contrôle des ordres de Zernike supérieurs du front d’onde de synthèse, ou bien plus généralement pour mesurer directement le front d’onde d’un rayonnement cohérent.Futuristic projects such as nuclear fusion power generation, or interstellar navigation by solar sails, require the use of a light source of extreme brightness. In order to increase the brightness of laser sources, my thesis work focused on the coherent beam combination of laser arrays. They led to the development of a new compact control process for the synthetic wavefront formed by the laser beam array. This process makes it possible to tailor the intensity pattern of the far field and thus control the angular distribution of energy emitted by the laser beam array. The process developed uses a phase/amplitude converter module with an integrated diffuser element. A method of measuring the transfer matrix of an optical system has been developed to characterize this field converter module. At any time, the synthetic wavefront is estimated by a phase recovery loop based on an alternating projections algorithm. This approximate calculation makes it possible to gradually adjust the phase relationships of the laser beam array to the desired arbitrary phase set. The process allows the control of a synthetic wavefront in less than 10 phase corrections, almost independently of the number of laser beams to be controlled. It is resistant to environmental defects and independent of the initial phase set. I demonstrated the compactness of the system studied by analyzing and controlling a 4 cm large synthetic pupil, composed of 16 beams, using an analysis module measuring only 30 cm. I also experimentally showed the control of the network phases of 16 to 100 laser beams with residual errors of λ/30 and λ/20 rms respectively. The capabilities of this method can be extended to control the higher Zernike orders of the synthetic wavefront, or more generally to directly measure the wavefront of coherent radiation

Nouveau procédé dynamique d’analyse et de contrôle du front d’onde synthétique de réseaux de lasers

Futuristic projects such as nuclear fusion power generation, or interstellar navigation by solar sails, require the use of a light source of extreme brightness. In order to increase the brightness of laser sources, my thesis work focused on the coherent beam combination of laser arrays. They led to the development of a new compact control process for the synthetic wavefront formed by the laser beam array. This process makes it possible to tailor the intensity pattern of the far field and thus control the angular distribution of energy emitted by the laser beam array. The process developed uses a phase/amplitude converter module with an integrated diffuser element. A method of measuring the transfer matrix of an optical system has been developed to characterize this field converter module. At any time, the synthetic wavefront is estimated by a phase recovery loop based on an alternating projections algorithm. This approximate calculation makes it possible to gradually adjust the phase relationships of the laser beam array to the desired arbitrary phase set. The process allows the control of a synthetic wavefront in less than 10 phase corrections, almost independently of the number of laser beams to be controlled. It is resistant to environmental defects and independent of the initial phase set. I demonstrated the compactness of the system studied by analyzing and controlling a 4 cm large synthetic pupil, composed of 16 beams, using an analysis module measuring only 30 cm. I also experimentally showed the control of the network phases of 16 to 100 laser beams with residual errors of λ/30 and λ/20 rms respectively. The capabilities of this method can be extended to control the higher Zernike orders of the synthetic wavefront, or more generally to directly measure the wavefront of coherent radiation.Des projets futuristes tels que la production d’énergie par fusion nucléaire, ou encore la navigation interstellaire par voiles solaires, requièrent l’utilisation d’une source de lumière de luminance extrême. Dans l’objectif d’augmenter la luminance de sources lasers, mes travaux de thèse ont porté sur la combinaison cohérente de réseaux de lasers. Ils ont conduit au développement d’un nouveau procédé de contrôle compact du front d’onde de synthèse formé par le réseau de faisceaux lasers. Ce procédé permet de sculpter à façon la figure intensimétrique du champ lointain et donc de contrôler la distribution angulaire d’énergie émise par le réseau de faisceaux lasers. Le procédé développé utilise un module convertisseur phase/amplitude intégrant un élément diffuseur. Une méthode de mesure de la matrice de transfert d’un système optique a été développée pour caractériser ce module convertisseur de champ. A tout instant, le front d’onde de synthèse est estimé par une boucle numérique de recouvrement de phase basée sur un algorithme à projections alternées. Ce calcul approché permet d’ajuster progressivement les relations de phases du réseau de faisceaux lasers jusqu’au jeu de phases arbitraire souhaité. Le procédé permet le contrôle d’un front d’onde de synthèse en moins de 10 corrections de phases, quasi-indépendamment du nombre de faisceaux lasers à contrôler. Il est robuste aux défauts environnementaux et indépendant du jeu de phases initiales. J’ai démontré la compacité du système étudié en analysant et contrôlant une pupille de synthèse de 4 cm de côté, constituée de 16 faisceaux, à l’aide d’un module d’analyse mesurant seulement 30 cm. J’ai également montré expérimentalement le contrôle des phases de réseaux de 16 à 100 faisceaux lasers avec des erreurs résiduelles valant respectivement λ/30 et λ/20 rms. Les capacités de cette méthode peuvent être étendues au contrôle des ordres de Zernike supérieurs du front d’onde de synthèse, ou bien plus généralement pour mesurer directement le front d’onde d’un rayonnement cohérent