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High-frequency and large amplitude current is a driving requirement for applications such as induction heating, wireless power transfer, power amplifier for magnetic resonant imaging, electronic ballasts, and ozone generators. Voltage-fed resonant inverters are normally employed, however, current-fed (CF) resonant inverters are a competitive alternative when the quality factor of the load is significantly high. The input current of a CF resonant inverter is considerably smaller than the output current, which benefits efficiency. A simple, parallel resonant tank is sufficient to create a high-power sinusoidal signal at the output. Additionally, input current is limited at the no-load condition, providing safe operation of the system. Drawbacks of the CF resonant inverter are associated with the implementation of the equivalent current source. A large input inductor is required to create an equivalent dc current source, to reduce power density and the bandwidth of the system. For safety, a switching stage is implemented using bidirectional voltage-blocking switches, which consist of a series connection of a diode and a transistor. The series diode experiences significant conduction loss because of large on-state voltage. The control of the output current amplitude for constant-frequency inverters requires a pre-regulation stage, typically implemented as a cascaded hard-switched dc/dc buck converter. The pre-regulation also reduces the efficiency. In this dissertation, a variety of CF resonant inverters with two input inductors and two grounded switches are investigated for an inductive-load driver with loaded quality factor larger than ten, constant and high-frequency (~500 kHz) operation, high reactive output power (~14 kVA), high bandwidth (~100 kHz), and high efficiency (over 95 %). The implementation of such system required to question the fundamental operation of the CF resonant inverter. The input inductance is reduced by around an order of magnitude, ensuring sufficient bandwidth, and allowing rich harmonic content in the input current. Of particular importance are fundamental and second harmonic components since they influence synchronization of the zero-crossing of the output voltage and the turn-on of the switches. The synchronization occurs at a particular frequency, termed synchronous frequency, and it allows for zero switching loss in the switches, which greatly boosts efficiency. The synchronous conditions were not know prior this work, and the dependence among circuit parameters, input current harmonics, and synchronous frequency are derived for the first time. The series diode of the bidirectional switch can reduce the efficiency of the system to below 90 %, and has to be removed from the system. The detrimental current-spikes can occur if the inverter is not operated in synchronous condition, such as in transients, or during parametric variations of the load coil. The resistance of the load coil has a wide variance, five times or more, while the inductance changes as well by a few percent. To accommodate for non-synchronous conditions, a low-loss current snubber is proposed as a safety measure to replace lossy diodes. The center-piece of the dissertation is the proposal of a two-phase zero-voltage switching buck pre-regulator, as it enables fixed frequency and synchronous operation of the inverter under wide parametric variations of the load. The synchronous operation is controlled by phase-shifting the switching functions of the pre-regulator and inverter. The pre-regulator reduces the dc current in the input inductors, which is a main contributor to current stress and conduction losses in the inverter switches. Total loss of the inverter switches is minimized since no switching loss is present and minimal conduction losses are allowed. The dc current in the input inductors, once seen as a means to transfer power to load, is now contradictory perceived as parasitic, and the power is transferred to the load using a fundamental frequency harmonic! The input current to the resonant tank, previously designed to be a square-wave, now resembles a sine-wave with very rich harmonic content. Additionally, the efficiency of the pre-regulator at heavy-load condition is improved by ensuring ZVS for with an additional inductive tank. The dissertation includes five chapters. The first chapter is an introduction to current-fed resonant inverters, applications, and state-of-the-art means to ensure constant frequency operation under load's parametric variations. The second chapter is dedicated to the optimization of the CF resonant inverter topology with a dc input voltage, two input inductors, and two MOSFETs. The topology is termed as a boost amplifier. If the amplifier operates away from the synchronous frequency, detrimental current spikes will flow though the switches since the series diodes are eliminated. Current spikes reduce the efficiency up to few percent and can create false functioning of the system. Operation at the synchronous frequency is achieved with large, bulky, input inductors, typically around 1-2 mH or higher, when the synchronous frequency follows the resonant frequency of the tank at 500 kHz. The input inductance cannot be reduced arbitrarily to meet the system bandwidth requirement, since the synchronous frequency is increased based on the inductance value. The relationship between the two (input inductance and the synchronous frequency) was unknown prior this work. The synchronous frequency is determined to be a complicated mathematical function of harmonic currents through the input inductors, and it is found using the harmonic decomposition method. As a safety feature, a current snubber is implemented in series with the resonant tank. Snubber utilizes a series inductance of cable connection between the tank and the switching stage, and it is more efficient than the previously employed series diodes. Topology optimization and detailed design procedure are provided with respect to efficiency and system dynamics. The mathematics is verified by a prototype rated at 14 kVA and 1.25 kW. The input inductance is reduced by around an order of magnitude, with the synchronous frequency increase of 2 %. The efficiency of the power amplifier reached 98.5 % and might be improved further with additional optimization. Silicon carbide MOSFETs are employed for their capability to operate efficiently at high frequency, and high temperature. The third chapter is dedicated to the development of the boost amplifier's large signal model using the Generalized State-space Averaging (GSSA) method. The model accurately predicts amplifier's transient and steady-state operation for any type of input voltage source (dc, dc with sinusoidal ripple, pulse-width modulated), and for either synchronous or non-synchronous operating frequency. It overcomes the limitation of the low-frequency model, which works well only for dc voltage-source input and at synchronous frequency. As the measure of accuracy, the zero-crossing of the resonant voltage is predicted with an error less than 2° over a period of synchronous operation, and for a range of interest for input inductance (25 μH – 1000 μH) and loaded-quality factor (10 – 50). The model is validated both in simulation and hardware for start-up transient and steady-state operation. It is then used in the synthesis of modulated output waveforms, including Hann-function and trapezoidal-function envelopes of the output voltage/current. In the fourth chapter, the GSSA model is employed in development of the PWM compensation method that ensures synchronous operation at constant frequency for the wide variation of the load. The boost amplifier is extended with a cascaded pre-regulator whose main purpose is to control the output resonant voltage. The pre-regulator is implemented as two switching half-bridges with same duty-cycle and phase-shift of 180°. The behavior of the cascaded structure is the same as of the buck converter, so the half-bridges are named buck pre-regulators. ZVS operation is ensured by putting an inductive tank between the half-bridges. Each output of half-bridges is connected to each of input inductors of the boost to provide the PWM excitation. Using the GSSA model, the synchronous condition and control laws are derived for the amplifier. Properties of the current harmonics in the input inductors are well examined. It is discovered that the dc harmonic, once used to transfer power, is unwanted (parasitic) since it increases conduction loss in switches of the boost. A better idea is to use the fundamental harmonic for power transfer, since it does not create loss in the switches. Complete elimination of the dc current is not feasible for constant frequency operation of the amplifier since the dc current depends on the load coil's resistance. However, significant mitigation of around 55 % is easily achievable. The proposed method improves significantly the efficiency of both the buck pre-regulator and the boost. Synchronous operation is demonstrated in hardware for fixed switching frequency of 480 kHz, power level up to 750 W, input voltage change from 300 V to 600 V, load coil's resistance change of three times, and load coil's inductance change of 3.5 %. Measured efficiency is around 95 %, with a great room for improvements. Chapter five summarizes key contributions and concludes the dissertation. / Ph. D.

Encoding and consolidation of memories are two processes within the hippocampus, and connected cortical networks, that recruit different circuit level dynamics to effectively process and pass information from brain region to brain region. In the hippocampal CA1 pyramidal layer local field potential (LFP), these processes take the form of theta and sharp wave ripples (SPW-Rs) for encoding and consolidation, respectively. As an animal runs through an environment, neurons become active at specific locations in the environment (place cells) increasing their firing rate, functionally representing these specific locations. These firing rate increases are organized within the local theta oscillations and sequential activation of many place cells creates a map of the environment. Once the animal stops moving and begins consummatory behaviors, such as eating, drinking, or grooming, theta activity diminishes, and large irregular activity (LIA) begins to dominate the LFP. Spontaneously, with the LIA, the place cells active during the experience are replayed during SPW-Rs in the same spatial order they were encountered in the environment. Both theta and SPW-R oscillations and their associated neuronal firing are necessary for effective place recognition as well as learning and memory. As such, interruption or termination of SPW-R events results in decreased learning performance over days. During exploration, the associated theta and sequential place cell activity is thought to encode the experience. During quiet restfulness or slow wave sleep (SWS), SPW-R events, that replay experience specific place sequences, are thought to be the signal by which systems consolidation progresses and the hippocampus guides cortical synaptic reorganization. The granular retrosplenial cortex (gRSC) is an associational area that exhibits high frequency oscillations (HFOs) during both hippocampal theta and SPW-Rs, and is potentially a period when the gRSC interprets incoming content from the hippocampus during encoding and systems consolidation. However, the precise laminar organization of synaptic currents supporting HFOs, whether the local gRSC circuitry can support HFOs without patterned input, and the precise coupling of hippocmapla oscillations to gRSC HFOs across brain states remains unknown. We aimed to answer these questions using in vivo, awake electrophysiological recordings in head-fixed mice that were trained to run for water rewards in a 1D virtual environment. We show that gRSC synaptic currents supporting HFOs, across all awake brain states, are exclusively localized to layer 2/3 (L2/3), even when events are detected within layer 5 (L5). Using focal optogenetics, both L2/3 and L5 can generate induced HFOs given a strong enough broad stimulation. Spontaneous gRSC HFOs occurring outside of SPW-Rs are highly comodulated with medial entorhinal cortex (MEC) generated high gamma in hippocampal stratum lacunosum moleculare. gRSC HFOs may serve a necessary role in communication between the hippocampus during SPW-Rs states and between the hippocampus, gRSC, and MEC during theta states to support memory consolidation and memory encoding, respectively. / Doctor of Philosophy / As an animal moves through an environment, individual neurons in the hippocampus, known as place cells, increase and decrease their firing rate as the animal enters and exits specific locations in the environment. Within an environment, multiple neurons become active in different locations, this cooperation of spiking in various locations creates a place map of the environment. Now let's say when the animal moved from one corner of the environment to another, place cells 'A', 'C', 'B', 'E', and 'D' became active in that order. This means, at any given point in the environment, the animal is standing in a venn-diagram-esque overlap of place fields, or locations individual place cells represent. A key question that entranced researchers for many years was how do these neurons know when to be active to not impinge on their neighbor's locations? The answer to this question rested with population electrical activity, known as the local field potential (LFP), that place cell activity is paced to. During active navigation through an environment, place cells activity is coupled to the phase of a slow ~8 hertz (Hz) theta oscillation. Within one theta cycle, or peak to peak, multiple place cells are active, representing the venn diagram of location the animal is in. Importantly, this theta activity and encoding of place cell activity is largely seen during active running or rapid eye movement (REM) sleep. During slow wave sleep (SWS), after an animal has experienced a specific environment and has created a place map, place cells are reactivated in the same order the animal experienced them in. From our previous example, the content of this reactivation would be the place cells 'A', 'C', 'B', 'E', and 'D' which all would be reactivated in that same order. These reactivations or replays occur during highly synchronous and fast LFP oscillations known as sharp wave-ripples (SPW-Rs). SPW-Rs are thought to be a key LFP event that drives memory consolidation and the eventual conversion of short-term memory into long-term memory. However, for consolidation to occur, connected cortical regions need to be able to receive and interpret the information within SPW-Rs. The granular retrosplenial cortex (gRSC) is one proposed region that serves this role. During SPW-Rs the superficial gRSC has been shown to exhibit high frequency oscillations (HFOs), which potentially serve the purpose for interpreting SPW-R content. However, HFOs have been reported during hippocampal theta, suggesting HFOs serve multiple purposes in interregional communication across different states. In this study, we found that naturally occurring gRSC HFOs occur exclusively in layer 2/3 across all awake brain states. Using focal optogenetic excitation we were able to evoke HFOs in both layer 2/3 and 5. Spontaneous gRSC HFOs occurring without SPW-Rs were highly comodulated with medial entorhinal cortex (MEC) generated high gamma in hippocampal stratum lacunosum moleculare. gRSC HFOs may serve a general role in supporting hippocampo-cortical dialogue during SPW-R and theta brain states to support memory consolidation and encoding, respectively.

This thesis deals with modeling, simulation and implementation of Load Commutated SCR based current source Inverter (LCI) fed squirrel cage induction motor drive with sinusoidal voltage and sinusoidal current. In the proposed system, the induction motor is fed by an LCI. A three level diode clamped voltage source inverter (VSI) is connected at the motor terminal with ac chokes connected in series with it. The VSI currents are controlled in such a manner that it injects the reactive current demanded by the induction motor and the LCI for successful commutation of the SCRs in the LCI. Additionally, it absorbs the harmonic frequency currents to ensure that the induction motor draws sinusoidal current. As a result, the nature of the motor terminal voltage is also sinusoidal. The concept of load commutation of the SCRs in the LCI feeding an induction motor load is explained with necessary waveforms and phasor diagrams. The necessity of reactive compensation by the active filter connected at the motor terminal for the load commutation of the thyristors, is elaborated with the help of analytical equations and phasor diagrams. The requirement of harmonic compensation by the same active filter to achieve sinusoidal motor current and motor voltage, is also described. Finally, to achieve the aforementioned induction motor drive, the VA ratings of the active filter (VSI) and the CSI with respect to VA rating of the motor, are determined theoretically. The proposed drive scheme is simulated under idealized condition. Simulation results show good steady state and dynamic response of the drive system. Load commutation of the SCRs in the LCI and the sinusoidal profile of motor current and voltage, have been demonstrated. As in LCI fed synchronous motor drives, a special mode of operation is required to run up the induction motor from standstill. As the SCRs of the LCI are load commutated, they need motor terminal voltages for commutation. At standstill these voltages are zero. So, a starting strategy has been proposed and adopted to start the motor with the aid of the current controlled VSI to accelerate until the motor terminal voltages are high enough for the commutation of the SCRs in the LCI. The proposed drive is implemented on an experimental setup in the laboratory. The IGBT based three level diode clamped VSI has been fabricated following the design of the standard module in the laboratory. A generalized digital control platform is also developed using a TMS320F2407A DSP. Two, three phase thyristor bridges with necessary firing pulse circuits have been used as the phase controlled rectifier and the LCI respectively. Appropriate protection scheme for such a drive is developed and adopted to operate the drive. Relevant experimental results are presented. They are observed to be in good agreement with the simulation results. The effect of capacitors connected at the output of the LCI in the commutation process of the SCRs in the LCI is studied and analyzed. From the analysis, it is understood that the capacitors form a parallel resonating pair with filter inductor and the motor leakage inductance, which results in an undesired oscillation in the terminal voltage during each of the commutation intervals leading to commutation failure. So, in the final system, the capacitors are removed to eliminate any chance of commutation failure of the SCRs in the LCI. It is shown by experiment that the commutation of the SCRs takes place reliably in the absence of the capacitors also. The commutation process is studied and analyzed without the capacitors to understand the motor terminal voltage waveform of the experimental results.

Bioimpedance spectroscopy is very useful in biomedical field as a safe and non-invasive technique. A stable and safe excitation current below than 0.5 mA for load impedances changing from 100 Ω to 10 kΩ in the full β-dispersion range from kHz up to 1 MHz is a big challenge for the design of the current source addressed by this thesis. For a good stability and high accuracy, the source should have a high output impedance. Different current source types in “current-mode approach” and “voltage-mode approach” were investigated and compared for usability in bioimpedance measurement systems. The “voltage-mode approach” with grounded load was proven to be more suitable and stable for biomedical measurements. Thereby the Tietze and the Howland circuit in dual configuration with negative feedback have shown the lowest error of the output current and the highest output impedance, where the improved Howland circuit in dual configuration with negative feedback is preferred because it has a simple structure, high accuracy and good stability. We suggest to improve the stability of the Howland circuit in dual configuration with negative feedback by introducing compensated operational amplifiers and to reduce stray capacitances at higher frequencies by adding gain compensation capacitor. We reach thereby an accuracy of 0.5% at low frequency and 0.9% at 1 MHz. With the realized accuracy of the designed voltage controlled current source, one decisive prerequisite for portable bioimpedance measurement system is achieved. In order to select the appropriate excitation signals for short measurement time, a comparative study of signals and their parameters was carried out. It leads to the selection of binary chirp signal as a suitable excitation signal due to its short measurement time about 100 μs, low crest factor lower than 2.8 and an energy efficiency higher than 54% in a very noisy signal. Simulation results show that the designed enhanced Howland current source excited by the binary chirp signal has low error and flatness in the whole range. / Die Bioimpedanzspektroskopie gewinnt aufgrund ihrer besonderen Eigenschaften als nicht-invasive, schonende Messmethode zunehmend an Bedeutung im biomedizinischen Bereich. Dabei ergeben sich besondere erausforderungen für den Entwurf der Stromquelle zur Realisierung eines stabilen und sicheren Anregungsstroms. Gefordert ist eine hohe Genauigkeit bis zu einem Maximalstrom von 0.5 mA in einem Frequenzbereich, der der β-Dispersion entspricht, von wenigen kHz bis hin zu 1 MHz. Die Stabilität muss bei variablen Lastimpedanzen im Bereich von 100 Ω bis 10 kΩ gewährleistet sein. Dafür muss die Stromquelle eine hohe Ausgangsimpedanz aufweisen. Diese Arbeit fokussiert auf den Entwurf von spannungsgesteuerten Stromquellen. Verschiedene Arten von Stromquellen wurden untersucht und verglichen. Der "Voltage-Modus-Ansatz" mit Masse-referenzierter Last hat sich als besser geeignet und stabiler für biomedizinische Messungen erwiesen. Die Tietze-Schaltung und diese Howland-Schaltung zeigen dabei die niedrigsten Fehler des Ausgangsstroms und die höchste Ausgangsimpedanz. Im direkten Vergleich besitzt die verbesserte Howland-Schaltung doch eine einfachere Struktur, höhere Genauigkeit und bessere Stabilität und wird daher gegenüber der Tietze-Schaltung bevorzugt. Um weitere Stabilitätsverbesserungen bei der Howland-Schaltung zu erreichen, werden zwei Maβnahmen vorgeschlagen. Zum einen werden kompensierte Operationsverstärker eingeführt und zum anderen wird der Einfluss von Streukapazitäten bei hohen Frequenzen minimiert indem die Verstärkung mit Kondensatoren kompensiert wird. Durch diese Maβnahmen wird eine Genauigkeit von 0.5% bei niedrigen Frequenzen und 0.9% bei 1 MHz ermöglicht. Mit dem neuen Entwurf der spannungsgesteuerten Stromquelle ist ein entscheidender Meilenstein für die Realisierung tragbarer Messsysteme der Bioimpedanz erreicht. Um eine kurze Messzeit zu realisieren wurde eine vergleichende Studie von Anregungssignalen und deren Signalparameter durchgeführt. Die Ergebnisse zeigen, dass binäre Chirp-Signale aufgrund der reduzierten Messzeit, des niedrigen Crest-Faktors unter 2.8 und hohe Energieeffizienz von mehr als 54% bei hohem Rauschlevel besonders geeignet sind. Simulationsergebnisse zeigen, dass die entwickelte Howland-Stromquelle zusammen mit einem binären Mehrfrequenzsignal den geringsten Amplitudenfehler im gesamten Frequenzbereich realisiert.

The interaction of an HVDC converter with the connected power system is of complex nature. An accurate model of the converter is required to study these interactions. The use of analytical small-signal converter models provides useful insight and understanding of the interaction of the HVDC system and the connected system components. In this thesis analytical models of the HVDC converters are developed in the frequency-domain by calculating different transfer functions for small superimposed oscillations of voltage, current, and control signals. The objective is to study the dynamic proprieties of the combined AC-DC interaction and the interaction between different HVDC converters with small signal analysis. It is well known that the classical Bode/Nyquist/Nichols control theory provides a good tool for this purpose if transfer functions that thoroughly describe the 'plant' or the 'process' are available. Thus, there is a need for such a frequency-domain model. Experience and theoretical calculation have shown that voltage/power stability is a very important issue for an HVDC transmission link based on conventional line-commutated thyristor-controlled converters connected to an AC system with low short circuit capacity. The lower the short circuit capacity of the connected AC system as compared with the power rating of the HVDC converter, the more problems related to voltage/power stability are expected. Low-order harmonic resonance is another issue of concern when line-commutated HVDC converters are connected to a weak AC system. This resonance appears due to the presence of filters and shunt capacitors together with the AC network impedance. With a weak AC system connected to the HVDC converter, the system impedances interact through the converter and create resonances on both the AC- and DC-sides of the converter. In general, these resonance conditions may impose limitations on the design of the HVDC controllers. In order to improve the performance of the HVDC transmission system when it is connected to a weak AC system network, a reactive compensator with a voltage source converter has been closely connected to the inverter bus. In this thesis it is shown that the voltage source converter, with an appropriate control strategy, will behave like a rotating synchronous condenser and can be used in a similar way for the dynamic compensation of power transmission systems, providing voltage support and increasing the transient stability of the converter. / QC 20100708

Laser Diodes (LDs) are semiconductor coherent lightening devices which are widely used in many fields such as defence, industry, medical and optical communications. They have advantageous characteristics such as having higher electrical-to-optical and optical-to-optical conversion efficiencies from pump source to useful output power when compared to flash lamps, which makes them the best devices to be used in range finding applications. Optical output power of lasers depends on current through LDs. Therefore, there is a relationship between operating life and work performance of LDs and performance of drive power supply. Even, weak drive current, small fluctuations of drive current can result in much greater fluctuations of optical output power and device parameters which will reduce reliability of LDs. In this thesis, a hardware for a fast and high power pulsed LD driver is designed for laser range finder and is based on linear current source topology. The driver is capable of providing pulses up to 120A with 250&mu / s pulse width and frequencies ranging from 20Hz to 40Hz. It provides current pulses for two LD arrays controlled with a proportional-integral (PI) controller and protect LDs against overcurrents and overvoltages. The proposed current control in the thesis reduces current regulation to less than 1% and diminishes overshoots and undershoots to a value less than 1% of steady-state value, which improves safe operation of LDs. Moreover, protection functions proposed in the thesis are able to detect any failure in driver and interrupt LD firing immediately, which guarantees safe operation of LDs.

Submitted by Morgana Silva (morgana_linhares@yahoo.com.br) on 2016-07-26T18:10:50Z No. of bitstreams: 1 arquivototal.pdf: 2752063 bytes, checksum: 886fc73f7f66099f1e033937798f6b7e (MD5) / Made available in DSpace on 2016-07-26T18:10:50Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2752063 bytes, checksum: 886fc73f7f66099f1e033937798f6b7e (MD5) Previous issue date: 2016-02-29 / This paper presents a block diagram modeling of a grid-independent photovoltaic power generation system, including the steps of DC regulation, voltage inversion, and control system based on dynamic simulations in Simulink / Matlab® exclusively using the built-in blocks available in its library. A well-known technique in literature called MPPT (maximum power point tracking) was used for tracking the maximum power of the photovoltaic generation. However, the control that was used to maintain a constant output voltage of the Push-Pull is based on a method that is similar to the MPPT, which configures a novelty of this research. The integration of modeling the entire PV system with these control systems is carried out in Simulink for investigaton and production of simulation results. An experimental platform that includes an emulator of photovoltaic panels, a 1 kW Push-Pull converter, a three-phase inverter with three arms and a hydraulic load constituided by a motor-pump was built in the laboratory. The experimental results corroborate the methodology that was used. / Este trabalho apresenta uma modelagem em diagramação de blocos de um sistema de geração de energia fotovoltaico isolado, incluindo as etapas de regulação CC, inversão de tensão e sistema de controle com base em simulações dinâmicas no ambiente Simulink/Matlab® utilizando, exclusivamente, os blocos built-in disponíveis em sua biblioteca. Uma técnica bem conhecida na literatura foi utilizada para o rastreio da máxima potência da geração fotovoltaica. No entanto, o controle utilizado para manter a tensão de saída constante do Push-Pull é baseado num método similar ao do rastreio da máxima potência, o que configura uma novidade deste trabalho. A integração da modelagem de todo o sistema fotovoltaico com estes sistemas de controle é realizada no ambiente Simulink para averiguação e produção dos resultados de simulação. Uma plataforma experimental que inclui um emulador de painéis fotovoltaicos, um Push-Pull de 1 kW de potência, um inversor trifásico de três braços e uma carga hidráulica constituída por um motobomba foi construída em laboratório. Os resultados experimentais corroboram a metodologia utilizada.

This work deals with the description and analysis of suitable methods for measurement of non-periodical high-level current pulses. For pulsed current source design and development a suitable measurement system is required. In this work shunt resistor, Rogowski sensor and magneto-optic sensor are presented. The analysis of their properties is performed in order to design a suitable sensor for test current pulse measurement. A design of Rogowski coil sensor has been made. An experimental measurement of current pulses with short time relations has been performed. The suitability of the coil sensor for non-harmonic waveforms measurement has been evaluated on the basis of measurement results. In case of the magneto-optic sensor a concept utilizing an optical fiber has been proposed. The design of the sensor has been performed also. Individual parts of the sensor were verified. Experimental magneto-optic sensors have been built and their properties have been studied.

This master’s thesis is an introduction to the measurement of changes in tissue impedance of blood flow by impedance plethysmography. Other chapters deal with the kinds of plethysmographs and their principles. The aim is to draft four-electrode impedance plethysmograph to measure changes in tissue impedance depending on blood flow. First, describe the individual blocks of the medical instrument. The practical part of the master’s thesis involves circuit design four-electrode plethysmograph. Given that a very important role in its function plays a constant current source operating at a frequency of 60kHz, this subset was implemented and verified its correct function. To draw component schemes used program EAGLE version 5.10.0.