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Evaluation and DSP based implementation of PWM approaches for single-phase DC-AC converters.Zhou, Lining. Chang, Jie. January 2005 (has links)
Thesis (M.S.)--Florida State University, 2005. / Advisor: Dr. Jie Chang, Florida State University, FAMU-FSU College of Engineering, Dept. of Electrical and Computer Engineering. Title and description from dissertation home page (viewed June 9, 2005). Document formatted into pages; contains xiii, 76 pages. Includes bibliographical references.
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Functional relevance of inhibitory and disinhibitory circuits in signal propagation in recurrent neuronal networksBihun, Marzena Maria January 2018 (has links)
Cell assemblies are considered to be physiological as well as functional units in the brain. A repetitive and stereotypical sequential activation of many neurons was observed, but the mechanisms underlying it are not well understood. Feedforward networks, such as synfire chains, with the pools of excitatory neurons unidirectionally connected and facilitating signal transmission in a cascade-like fashion were proposed to model such sequential activity. When embedded in a recurrent network, these were shown to destabilise the whole network’s activity, challenging the suitability of the model. Here, we investigate a feedforward chain of excitatory pools enriched by inhibitory pools that provide disynaptic feedforward inhibition. We show that when embedded in a recurrent network of spiking neurons, such an augmented chain is capable of robust signal propagation. We then investigate the influence of overlapping two chains on the signal transmission as well as the stability of the host network. While shared excitatory pools turn out to be detrimental to global stability, inhibitory overlap implicitly realises the motif of lateral inhibition, which, if moderate, maintains the stability but if substantial, it silences the whole network activity including the signal. Addition of a disinhibitory pathway along the chain proves to rescue the signal transmission by transforming a strong inhibitory wave into a disinhibitory one, which specifically guards the excitatory pools from receiving excessive inhibition and thereby allowing them to remain responsive to the forthcoming activation. Disinhibitory circuits not only improve the signal transmission, but can also control it via a gating mechanism. We demonstrate that by manipulating a firing threshold of the disinhibitory neurons, the signal transmission can be enabled or completely blocked. This mechanism corresponds to cholinergic modulation, which was shown to be signalled by volume as well as phasic transmission and variably target classes of neurons. Furthermore, we show that modulation of the feedforward inhibition circuit can promote generating spontaneous replay at the absence of external inputs. This mechanism, however, tends to also cause global instabilities. Overall, these results underscore the importance of inhibitory neuron populations in controlling signal propagation in cell assemblies as well as global stability. Specific inhibitory circuits, when controlled by neuromodulatory systems, can robustly guide or block the signals and invoke replay. This mounts to evidence that the population of interneurons is diverse and can be best categorised by neurons’ specific circuit functions as well as their responsiveness to neuromodulators.
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Přechodové děje na výstupu LTI systému druhého řádu se spojitým časem řízeného pulsně šířkovou modulací / Transient effect at the output of a continuous-time LTI second order system controlled pulse-width modulationPetera, Martin January 2016 (has links)
The aim of this thesis is to determine the size of overshoot produced at the output of a linear continuous second order system controlled by pulse width modulation depending on the period and duty cycle of the modulation and system parameters. This thesis contains analytic calculation of the size of overshoot produced at the output of the second order system with damping ratio > 0, except the damping ratio equals to 1 (i.e. both underdamped and damped system) depending on period and duty cycle of the modulation. This thesis also includes a comparison of partial analytic results to numerical simulation in Matlab program and also with measurement at second order system model.
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A microcontroller-based Electrochemical Impedance Spectroscopy Platform for Health Monitoring SystemsBhatnagar, Purva 16 October 2015 (has links)
No description available.
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Algoritmos Genéticos para Síntese de Filtros Aplicados em Controle por Modo Deslizante. / Genetic Algorithms for Synthesis of Filters Applied in a Sliding Mode Control.Felipe da Trindade do Nascimento 20 July 2010 (has links)
Nesta Dissertação propõe-se a aplicação de algoritmos genéticos para a síntese de filtros
para modular sinais de controladores a estrutura variável e modo deslizante. A modulação
do sinal de controle reduz a amplitude do sinal de saída e, consequentemente, pode
reduzir o consumo de energia para realizar o controle e o chattering. Esses filtros também
são aplicados em sistemas que possuem incertezas paramétricas nos quais nem todas as
variáveis de estado são medidas. Nesses sistemas, as incertezas nos parâmetros podem
impedir que seus estados sejam estimados com precisão por observadores. A síntese
desses filtros necessita da obtenção da envoltória, que é o valor máximo da norma de cada
resposta impulsiva admissível no sistema. Após este passo, é sintetizado um filtro que
seja um majorante para a envoltória. Neste estudo, três métodos de busca da envoltória
por algoritmos genéticos foram criados. Um dos métodos é o preferido, pois apresentou
os melhores resultados e o menor tempo computacional. / This thesis proposes the application of genetic algorithms for the synthesis of filters which
modulate signals of variable structure sliding mode controllers. The modulation of the
control signal reduces the amplitude of the output signal and thus can reduce power
consumption and chattering. These filters are also applied to systems with parametric
uncertainties and unmeasured state variables. In these systems, the uncertainties can
impair the accurate estimation of the state by means of observers. For the synthesis of
these filters, it is necessary to obtain the envelope which is the maximum norm of each
impulse response admissible for the system. After this step, a filter is synthesized to be
an upper bound for the envelope. In this study, three methods of search of the envelope
by genetic algorithms were developed. One of these methods has been giving the best
results and needs the least computational time.
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Algoritmos Genéticos para Síntese de Filtros Aplicados em Controle por Modo Deslizante. / Genetic Algorithms for Synthesis of Filters Applied in a Sliding Mode Control.Felipe da Trindade do Nascimento 20 July 2010 (has links)
Nesta Dissertação propõe-se a aplicação de algoritmos genéticos para a síntese de filtros
para modular sinais de controladores a estrutura variável e modo deslizante. A modulação
do sinal de controle reduz a amplitude do sinal de saída e, consequentemente, pode
reduzir o consumo de energia para realizar o controle e o chattering. Esses filtros também
são aplicados em sistemas que possuem incertezas paramétricas nos quais nem todas as
variáveis de estado são medidas. Nesses sistemas, as incertezas nos parâmetros podem
impedir que seus estados sejam estimados com precisão por observadores. A síntese
desses filtros necessita da obtenção da envoltória, que é o valor máximo da norma de cada
resposta impulsiva admissível no sistema. Após este passo, é sintetizado um filtro que
seja um majorante para a envoltória. Neste estudo, três métodos de busca da envoltória
por algoritmos genéticos foram criados. Um dos métodos é o preferido, pois apresentou
os melhores resultados e o menor tempo computacional. / This thesis proposes the application of genetic algorithms for the synthesis of filters which
modulate signals of variable structure sliding mode controllers. The modulation of the
control signal reduces the amplitude of the output signal and thus can reduce power
consumption and chattering. These filters are also applied to systems with parametric
uncertainties and unmeasured state variables. In these systems, the uncertainties can
impair the accurate estimation of the state by means of observers. For the synthesis of
these filters, it is necessary to obtain the envelope which is the maximum norm of each
impulse response admissible for the system. After this step, a filter is synthesized to be
an upper bound for the envelope. In this study, three methods of search of the envelope
by genetic algorithms were developed. One of these methods has been giving the best
results and needs the least computational time.
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