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In this thesis, the design of a voltage-source inverter (VSI)-based three-phase impedance analyzer's perturbation injection unit (PIU) is described including all relevant power stage and control design. Both series and shunt injection are examined from .1 Hz to 1000Hz. Both types of injection are performed using only energy from the system under test stored in a DC link capacitor. Sinusoidal, square (pulse), and chirp perturbation waveforms are explored. Results from a constructed realization of the design are presented, and the limits of the device characterized. The maximum achievable perturbation power is 10 kW in shunt and 8 kW in series on a 460 V, 100 kW bus. Using the same conditions, maximum power is achievable from 10Hz to 100Hz, at .1Hz, .72 kW is achievable, and at 1000Hz, 6.0 kW is achievable. / Master of Science

Biological cells like any other material do conduct electricity. Though they come across as insulators, the resistance to the flow of current, i.e. impedance, could be used to characterize the cell itself. In this aspect, the impedance of cells can be a promising tool to investigate the state of the cell. A simple way of measuring the impedance would be a planar-microelectrode method. The cells are contained in culture medium while measurements are taken with micro-electrodes fabricated on top of a substrate. Since both the probe "tips" do not come in contact with the probed object, the impedance to be measured includes some components apart from that contributed by the cells. There have been publications reporting the usage of impedance of a cell to determine changes in the state of cells due to healing, drug candidate testing, functional genomic studies and so on. In this thesis, an effort has been made to measure the impedance of cells. Further, a component of the sensor, the passivation layer has been investigated for its contribution to the measured impedance in a quantitative manner. / Master of Science

"Ischemia is a condition of decreased tissue viability caused by a lack of perfusion, which prevents the delivery of oxygen and nutrients to biological tissue. Ischemia plays a major role in many clinical disorders, yet there are limited means by which tissue viability can be assessed. The long-term objective of this research is to develop a non-invasive or non-contact instrument for quantifying human tissue ischemia. Skeletal muscle ischemia is evaluated at this stage because skeletal muscle is easily accessible, its ischemia represents a clinical problem, and it can endure short periods of ischemia without suffering permanent injury. The ischemia monitor designed for this study is based on impedance spectroscopy, the measurement of tissue impedance at various frequencies. This study had three major goals. The first goal was to improve upon the design of the ischemia monitor to achieve optimal system performance in a clinical environment. Major considerations included electrode sterility, instrument mobility, and electrosurgical unit interference. The second goal was to collect both impedance and pH data from human subjects undergoing tourniquet surgeries, which induce skeletal muscle ischemia and result in changes of the tissue's pH and impedance. The average in recorded pH during ischemia was 0.0053 pH units/minute and the average change in Ro was -0.1481 Ohms/minute. The third goal was to develop a relationship between parameters of tissue impedance and pH utilizing neural networks. This goal was accomplished in three stages. First, the optimal neural network type for classifying impedance data and pH values was determined. Based on these results, the backpropagation neural network was utilized for all subsequent work. Then, the input parameters of the neural network were optimized using previously collected data. The number of inputs to the previously developed neural network were reduced by 35% (13/20) with a maximum of a 3% reduction in neural network performance. Finally, the neural network was trained and tested using human impedance and pH data. The network was able to correctly estimate tissue pH values with an average error of 0.0440 pH units. Through the course of this research the ischemia monitor based on impedance spectroscopy was improved, a methodology for the use of the instrument in the operating room was developed, and a preliminary relationship between parameters of impedance spectra and pH was established. The results of this research indicate the feasibility of the instrument to monitor both pH and impedance in a clinical setting. Additionally, it was demonstrated that impedance data collected non-invasively could be used to estimate the pH and level of ischemia in human skeletal muscle."

by Ling Chao Dong. / Publication date from spine. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves [102]-107). / ABSTRACT --- p.iii / ACKNOWLEDGEMENTS --- p.v / LIST OF ABBREVIATIONS --- p.vi / Chapter CHAPTER 1 --- Introduction / Chapter 1.1 --- Physiological measurement by EBI technique --- p.1 -1 / Chapter 1.2 --- Application of the EBI technique in the human thorax --- p.1 -2 / Chapter 1.3 --- Development in EIR measurement-An overview --- p.1 -4 / Chapter 1.4 --- Project objective --- p.1-7 / Chapter 1.5 --- Problems to be solved for EBI data acquisition system --- p.1-8 / Chapter 1.6 --- Main contribution of this project --- p.1 -8 / Chapter 1.7 --- Thesis outline --- p.1-9 / Chapter CHAPTER 2 --- Principles of The EBI Technique for Cardiopulmonary System / Chapter 2.1 --- The data acquisition system (DAS) --- p.2-1 / Chapter 2.1.1 --- Impedance measurement --- p.2-1 / Chapter 2.1.2 --- Data extraction and collection --- p.2-3 / Chapter 2.2 --- Constant current source --- p.2-3 / Chapter 2.3 --- Single-source multi-channel EBI controller --- p.2-5 / Chapter 2.4 --- Computer interface --- p.2-6 / Chapter 2.5 --- Tissue impedance and impedance change --- p.2-7 / Chapter 2.5.1 --- Impedance of living tissue --- p.2-7 / Chapter 2.5.2 --- Origins of impedance change --- p.2-8 / Chapter 2.6 --- Cardiovascular physiology in human body --- p.2-10 / Chapter 2.6.1 --- Structure and function of the circulatory system --- p.2-10 / Chapter 2.6.2 --- Principles of hemodynamics in pulmonary circulation --- p.2-12 / Chapter 2.7 --- Clinical application of the EIR waveform --- p.2-15 / Chapter 2.7.1 --- Physiological basis --- p.2-15 / Chapter 2.7.2 --- Clinical application --- p.2-16 / Chapter CHAPTER 3 --- The Composition of EIR Signal / Chapter 3.1 --- Introduction --- p.3-1 / Chapter 3.1.1 --- The impedance change in the transthoracic section --- p.3-1 / Chapter 3.1.2 --- Origins of impedance change in pulmonary circulation --- p.3-2 / Chapter 3.2 --- Examination of contribution of impedance sources via electrolytic tank model --- p.3-3 / Chapter 3.2.1 --- Electrolytic tank set-up --- p.3-3 / Chapter 3.2.2 --- Electrolytic tank procedure --- p.3-4 / Chapter 3.2.3 --- Experimental results and discussion --- p.3-5 / Chapter 3.3 --- The interference behaviour via computer simulation --- p.3-8 / Chapter 3.3.1 --- 2D numerical model --- p.3-9 / Chapter 3.3.2 --- Computer simulation --- p.3-10 / Chapter 3.3.3 --- Results and discussion --- p.3-11 / Chapter 3.4 --- The variation of EIR waveform with electrode size --- p.3-12 / Chapter 3.4.1 --- An electronic model --- p.3-12 / Chapter 3.4.2 --- A simulated source of impedance change in pulmonary circuit --- p.3-16 / Chapter 3.4.3 --- Variation of EIR waveform via computer simulation --- p.3-18 / Chapter 3.4.4 --- Computer simulation results and discussion --- p.3-20 / Chapter 3.5 --- Discussions --- p.3-20 / Chapter 3.6 --- Conclusion --- p.3-21 / Chapter CHAPTER 4 --- A Guard Electrode System to Improve the EIR Measurement / Chapter 4.1 --- Introduction --- p.4-1 / Chapter 4.2 --- Normal electrode system --- p.4-2 / Chapter 4.2.1 --- Normal electrode configuration --- p.4-2 / Chapter 4.2.2 --- Current-guarding technique for the constant-voltage system --- p.4-2 / Chapter 4.3 --- Electric field guarding --- p.4-3 / Chapter 4.4 --- Methods of study --- p.4-4 / Chapter 4.5 --- Results --- p.4-5 / Chapter 4.4.1 --- The change of electric field distribution with guarding --- p.4-5 / Chapter 4.4.2 --- Result from electrolytic tank simulation --- p.4-5 / Chapter 4.4.3 --- Variation of EIR waveform with/without guarding in human thorax --- p.4-6 / Chapter 4.5 --- Discussions and conclusion --- p.4-6 / Chapter CHAPTER 5 --- Human Measurements / Chapter 5.1 --- Introduction --- p.5-1 / Chapter 5.2 --- Variation of EIR waveform from normal human body --- p.5-2 / Chapter 5.2.1 --- Methods --- p.5_2 / Chapter 5.2.2 --- The variation of EIR waveform with electrode position and size --- p.5-3 / Chapter 5.3 --- Clinical observation --- p.5-4 / Chapter 5.3.1 --- What is PTMV --- p.5-4 / Chapter 5.3.2 --- Observing EIR waveform during the PTMV operation --- p.5-5 / Chapter 5.3.3 --- Results and discussion --- p.5-5 / Chapter 5.4 --- EIR for use in PTMV operation --- p.5-7 / Chapter 5.4.1 --- Conventional diagnostic and monitoring methods for PTMV --- p.5-7 / Chapter 5.4.2 --- The characteristic of EIR waveform with mitral stenosis --- p.5-7 / Chapter 5.4.3 --- Use of EIR as an assessing/monitoring tool for PTMV operation --- p.5-8 / Chapter 5.4.4 --- Methodology in this study --- p.5-8 / Chapter 5.4.5 --- Result and discussion --- p.5-9 / Chapter 5.5 --- Conclusion --- p.5-10 / Chapter CHAPTER 6 --- Recapitulation and Topic for Future Investigation / Chapter 6.1 --- Recapitulation --- p.6-1 / Chapter 6.2 --- Topics for future investigation --- p.6-3 / Chapter 6.2.1 --- Improvement to the DAS --- p.6-3 / Chapter 6.2.1 --- Data analysis for PTMV --- p.6-3 / REFERENCES --- p.R-1 / APPENDICES / Chapter A. --- Circuit diagram of electrical bio-impedance source simulator --- p.A-l / Chapter B. --- Circuit diagram of the electrical bio-impedance detector --- p.A-2 / Chapter C. --- Circuit diagram of multi-channel controller for multi-EBI detection --- p.A-3 / Chapter D. --- List of publications --- p.A-4

Abstract There is a need in medicine and research for noninvasive, painless, safe and simple bed-side techniques to measure physiological processes associated with muscle function and activity. Bioelectrical Impedance Analysis (BIA) is a widely used, noninvasive, painless, safe and simple procedure for the measurement of body composition. However, although capable of producing accurate and reproducible data, it is known to be prone to movement artifacts. This poses the interesting question “Could impedance changes be used to monitor movement and, consequently, be related to muscle function or activity?” This project investigated the utility of impedance change as a monitoring technique for physiological processes that involve movement such as muscular contraction, the calf muscle pump, and swallowing. The impedance of leg muscle segments during locomotion, whilst riding a stationary exercise cycle, was measured at discrete frequencies and by bioimpedance spectroscopy to monitor muscle function or activity. Impedance traces were compared to information obtained by electromyography (EMG). Impedance, at a discrete frequency, was able to measure the cadence of cycling and its magnitude was related to the position of the pedal during the pedal cycle. When the cycling action was measured by bioimpedance spectroscopy, R0 and Zc showed a statistically significant difference, (p<0.05), between all angles of the pedal crank cycle while R∞ showed a statistically significant difference between angles in the lower hemisphere of the pedal crank cycle. The cyclical changes in impedance during cycling may be attributed to changes in shape and volume of the muscle during contraction as well as a volume change due to blood and lymph being pumped from the limb by the action of the calf muscle pump. Based on procedures used in the cycling studies, an impedance-based method for the measurement of calf muscle pump function during an exercise protocol, originally designed for use with air plethysmography, was developed. It was shown that impedance measured at 5 kHz provides a simple, non-invasive method for the measurement of the ejection fraction and ejection volume of the calf muscle pump as well as other haemodynamic variables. The impedance-based method was less technically challenging than accepted volumetric methods, such as air plethysmography and strain gauge plethysmography, and non-invasive c.f. ambulatory venous pressure, enabling it to be used repeatedly. Muscle function and activity is not confined to the legs so impedance changes in the arm and forearm during exercise were measured. Impedance measurements, at discrete frequencies and using bioimpedance spectroscopy, of the forearm during contractions of the hand were able to distinguish the difference between a ramp and a pulse contraction. When the impedance of the arm and forearm were plotted against the angle of the forearm to the horizontal during a bicep curl, there was an hysteresis effect. Impedance traces of a bicep curl were compared to an EMG trace of the same action. The larynx is a hollow muscular organ situated in the front of the neck above the trachea consisting of a framework of cartilages bound together by muscles and ligaments. The two major functions of the larynx are deglutition and phonation. Dysphagia, which is becoming more prevalent as the population ages, is defined as difficulty in swallowing thin liquids such as water or juices which splash into the trachea because the patient is unable to control the thin liquid bolus. Aspiration pneumonia and dehydration can be prevented by using thickened liquids which allow patients to achieve a safer swallowing response, but it is difficult to assess this response without interfering with the swallowing process. Impedance pharynography (IPG) is a technique using BIA to monitor an impedance waveform of the swallowing process that presents no radiation hazard to the patient, is non-invasive and does not require specialist trained personnel to operate it. Resistance changes across the neck were measured while subjects swallowed solutions of different viscosities. The resistance changes were distinctive and reproducible for each of the solutions of different viscosities which were swallowed. Measuring the function of the larynx by this method could be useful in the diagnosis and treatment of dysphagia. In conclusion, the studies described in this thesis demonstrate the potential usefulness of the measurement of change in impedance as a measure of muscle activity. Impedance-based methods can measure volume changes associated with changes in cross-sectional area of the muscles involved in contraction as well as compartmental fluid changes caused by the force of the contraction on the surrounding tissues including the vasculature. In particular, measuring the ejection fraction and other haemodynamic variables of the calf muscle pump by impedance has the potential to become the method of choice in the future because it is easy to use, inexpensive, non-invasive, safe, and hygenic. Measuring resistance changes across the neck during swallowing yields distinctive waveforms with features corresponding to the physiological phases of the swallowing process as well as identifying distinctive swallowing patterns associated with the different viscosities of liquids swallowed. Function of the larynx and the associated diseases of the larynx will potentially be easier to diagnose and treat with a safe, non-invasive, inexpensive, portable bed-side method of assessment such as BIA.

Photovoltaic (PV) conversion of solar energy appears to be one of the most promising ways of meeting the increasing future energy demand. In space, photovoltaic power source is the only alternative. The demand for higher power has necessitated the use of high speed switching charge controller and power conditioner. To design an efficient and reliable switching charge controller, the static (I-V) and dynamic (AC) characteristics of a solar cell need to be understood. The AC parameters of a solar cell can be measured either by Frequency Domain technique or by Time Domain technique. In frequency domain technique, a small signal is applied about the operating point and the AC parameters are measured. Hence, in the frequency domain technique the steady state values of AC parameters at a particular operating condition are measured. In time domain technique, a transient measurement is made where the cell voltage varies from short-circuit to open circuit or vice versa. Hence, this technique gives only the time constant of a solar cell. The impedance spectroscopy is a frequency domain technique widely used in electro chemistry to study battery characteristics. In the present investigation, the impedance spectroscopy is proposed for measuring the AC parameters of solar cells. An experimental set-up has been developed to measure the solar cell AC parameters. The AC parameters of Silicon (BSR and BSFR) solar cells and GaAs/Ge solar cells are measured using impedance spectroscopy (IS). The cell capacitance, the parallel resistance and the series resistance are measured and compared. GaAs/Ge solar cell has shown only transition Capacitance throughout its operating range while silicon (BSR and BSFR) solar cells exhibited both transition and diffusion capacitances. Theoretical and experimental values of the cell parallel resistance are compared and are in good agreement. While the diode factor in silicon solar cell varies from 2 to 1, where as in GaAs/Ge solar cell it varies from 4 to 2 to 1. Measurements conducted using open circuit voltage buildup (time domain technique) on silicon BSR solar cell shows that the collected data can be used for the restricted purpose of measuring cell transient response. The dime domain technique could not estimate the solar cell. It may be noted that the impedance spectroscopy assumes piece-wise linearity of the solar cell characteristics, lending itself for easy measurement and modeling. This assumption is valid as the signal amplitude is less than thermal voltage (VT). Since, the parameters are measured under steady state, the values are more stable and accurate. An attempt has also been made to correlate the measured AC parameters with the requirements of switching charge controllers. These correlations can be used to design the switching controllers for device rating, circuit stability and other aspects.

Jitter and noise on package and printed circuit board interconnects are limiting factors in the performance of high speed digital channels. The simultaneous switching noise (SSN) induced by the return path discontinuities (RPDs) is a major source of noise and jitter on the signal interconnects of these channels. Therefore, optimal design of the power delivery network (PDN) is required to reduce SSN induced noise and jitter and improve the performance of high speed channels. The design of PDN is done in frequency domain whereas jitter and noise are time domain events. As a result, multiple iterations between frequency domain design of PDN and time domain analysis of noise and jitter are required before a design is taped out. A new methodology to correlate PDN impedance with jitter and voltage margin is presented in this thesis. Using this methodology, it would be possible to estimate jitter and noise from the PDN impedance and reduce the iterations involved in freezing the PDN design. The SSN induced at a given RPD is proportional to the PDN impedance at that RPD. As a result, the jitter and the noise can be correlated to the PDN impedance. The PDN impedance is a function of frequency and has alternate local minima and local maxima at resonances and anti-resonances respectively. The anti-resonances in the PDN impedance at the RPD cause significant increase in the insertion loss of signal whose return current is disrupted at that RPD. The increase in the insertion loss attenuates significant harmonics of the signal degrading its rise/fall times and voltage levels. This results in reduction of timing and voltage margins of the signal. Thus, based on the insertion loss profile and harmonic content of the signal, an estimate of jitter and noise on the signal can be made. Passive test vehicles consisting of microstrips with RPDs have been designed and fabricated to demonstrate the proof of concept through both simulations and measurements. Suitable placement of decoupling capacitors is suggested to reduce the PDN impedance below the target impedance and to minimize coupling between two noise ports on the PDN. Genetic algorithm to optimize the selection and placement of decoupling capacitors has been implemented. The efficacy of the algorithm has been demonstrated by testing it on a power delivery networks consisting of a simple power/ground plane pair.

Abstract There is a need in medicine and research for noninvasive, painless, safe and simple bed-side techniques to measure physiological processes associated with muscle function and activity. Bioelectrical Impedance Analysis (BIA) is a widely used, noninvasive, painless, safe and simple procedure for the measurement of body composition. However, although capable of producing accurate and reproducible data, it is known to be prone to movement artifacts. This poses the interesting question “Could impedance changes be used to monitor movement and, consequently, be related to muscle function or activity?” This project investigated the utility of impedance change as a monitoring technique for physiological processes that involve movement such as muscular contraction, the calf muscle pump, and swallowing. The impedance of leg muscle segments during locomotion, whilst riding a stationary exercise cycle, was measured at discrete frequencies and by bioimpedance spectroscopy to monitor muscle function or activity. Impedance traces were compared to information obtained by electromyography (EMG). Impedance, at a discrete frequency, was able to measure the cadence of cycling and its magnitude was related to the position of the pedal during the pedal cycle. When the cycling action was measured by bioimpedance spectroscopy, R0 and Zc showed a statistically significant difference, (p<0.05), between all angles of the pedal crank cycle while R∞ showed a statistically significant difference between angles in the lower hemisphere of the pedal crank cycle. The cyclical changes in impedance during cycling may be attributed to changes in shape and volume of the muscle during contraction as well as a volume change due to blood and lymph being pumped from the limb by the action of the calf muscle pump. Based on procedures used in the cycling studies, an impedance-based method for the measurement of calf muscle pump function during an exercise protocol, originally designed for use with air plethysmography, was developed. It was shown that impedance measured at 5 kHz provides a simple, non-invasive method for the measurement of the ejection fraction and ejection volume of the calf muscle pump as well as other haemodynamic variables. The impedance-based method was less technically challenging than accepted volumetric methods, such as air plethysmography and strain gauge plethysmography, and non-invasive c.f. ambulatory venous pressure, enabling it to be used repeatedly. Muscle function and activity is not confined to the legs so impedance changes in the arm and forearm during exercise were measured. Impedance measurements, at discrete frequencies and using bioimpedance spectroscopy, of the forearm during contractions of the hand were able to distinguish the difference between a ramp and a pulse contraction. When the impedance of the arm and forearm were plotted against the angle of the forearm to the horizontal during a bicep curl, there was an hysteresis effect. Impedance traces of a bicep curl were compared to an EMG trace of the same action. The larynx is a hollow muscular organ situated in the front of the neck above the trachea consisting of a framework of cartilages bound together by muscles and ligaments. The two major functions of the larynx are deglutition and phonation. Dysphagia, which is becoming more prevalent as the population ages, is defined as difficulty in swallowing thin liquids such as water or juices which splash into the trachea because the patient is unable to control the thin liquid bolus. Aspiration pneumonia and dehydration can be prevented by using thickened liquids which allow patients to achieve a safer swallowing response, but it is difficult to assess this response without interfering with the swallowing process. Impedance pharynography (IPG) is a technique using BIA to monitor an impedance waveform of the swallowing process that presents no radiation hazard to the patient, is non-invasive and does not require specialist trained personnel to operate it. Resistance changes across the neck were measured while subjects swallowed solutions of different viscosities. The resistance changes were distinctive and reproducible for each of the solutions of different viscosities which were swallowed. Measuring the function of the larynx by this method could be useful in the diagnosis and treatment of dysphagia. In conclusion, the studies described in this thesis demonstrate the potential usefulness of the measurement of change in impedance as a measure of muscle activity. Impedance-based methods can measure volume changes associated with changes in cross-sectional area of the muscles involved in contraction as well as compartmental fluid changes caused by the force of the contraction on the surrounding tissues including the vasculature. In particular, measuring the ejection fraction and other haemodynamic variables of the calf muscle pump by impedance has the potential to become the method of choice in the future because it is easy to use, inexpensive, non-invasive, safe, and hygenic. Measuring resistance changes across the neck during swallowing yields distinctive waveforms with features corresponding to the physiological phases of the swallowing process as well as identifying distinctive swallowing patterns associated with the different viscosities of liquids swallowed. Function of the larynx and the associated diseases of the larynx will potentially be easier to diagnose and treat with a safe, non-invasive, inexpensive, portable bed-side method of assessment such as BIA.