This paper presents a technique for creating virtual electrodes between physical electrodes in a retinal prosthesis. The technique involves stimulating two adjacent physical electrodes with identical pulses that have pulse widths too short to activate neurons on their own. However, one pulse is time-offset from the other. This results in a virtual electrode appearing in the center of the two physical electrodes, with a pulse width that is the sum of the two individual pulses. This combined pulse width is long enough to activate neurons. Experimental results show that when two electrodes 250 μm apart were stimulated with 1 ms pulses offset by 1 ms, a virtual electrode appeared between them with a pulse width of 2 ms, matching the expected results. This virtual electrode technique could help increase the effective resolution of
Wireless sensor nodes are usually deployed in not easily accessible places to provide solution to a wide
range of application such as environmental, medical and structural monitoring. They are spatially
distributed and as a result are usually powered from batteries. Due to the limitation in providing power
with batteries, which must be manually replaced when they are depleted, and location constraints in
wireless sensor network causes a major setback on performance and lifetime of WSNs. This difficulty in
battery replacement and cost led to a growing interest in energy harvesting. The current practice in energy
harvesting for sensor networks is based on practical and simulation approach. The evaluation and
validation of the WSN systems is mostly done using simulation and practical implementation. Simulation is
widely used especially for its great advantage in evaluating network systems. Its disadvantages such as the
long time taken to simulate and not being economical as it implements data without proper analysis of all
that is involved ,wasting useful resources cannot be ignored. In most times, the energy scavenged is directly
wired to the sensor nodes. We, therefore, argue that simulation – based and practical implementation of
WSN energy harvesting system should be further strengthened through mathematical analysis and design
procedures. In this work, we designed and modeled the energy harvesting system for wireless sensor nodes
based on the input and output parameters of the energy sources and sensor nodes. We also introduced the
use of supercapacitor as buffer and intermittent source for the sensor node. The model was further tested in
a Matlab environment, and found to yield a very good approach for system design.
Design and Optimization of Inductively Coupled Spiral Square Coils for Bio-Im...IJECEIAES
Due to the development of biomedical microsystems technologies, the use of wireless power transfer systems in biomedical application has become very largely used for powering the implanted devices. The wireless power transfer by inductive resonance coupling link, is a technic for powering implantable medical devices (IMDs) between the external and implanted circuits. In this paper we describe the design of an inductive resonance coupling link using for powering small bio-implanted devices such as implantable bio-microsystem, peacemaker and cochlear implants. We present the reduced design and an optimization of small size obtained spiral coils of a 9.5 mm2 implantable device with an operating frequency of 13.56 MHz according to the industrial scientific-medical (ISM). The model of the inductive coupling link based on spiral square coils design is developed using the theoretical analysis and optimization geometry of an inductive link. For a mutual distance between the two coils at 10mm, the power transfer efficiency is about 79% with , coupling coefficient of 0.075 and a mutual inductance value of 2µH. In comparison with previous works, the results obtained in this work showed better performance such as the weak inter coils distance, the hight efficiency power transfer and geometry.
This document describes a study that tested the effectiveness of using Signa gel with tripolar concentric ring electrodes (TCREs) to record electroencephalography (EEG) signals from the brain. TCREs are a type of electrode that can help reduce noise in EEG recordings compared to conventional disc electrodes. The study found that 10 mm diameter TCREs attached with Signa gel were able to clearly detect alpha wave brain activity, but smaller 6 mm and 4 mm TCREs were less consistent, possibly due to noisy connections to the recording interface. The results suggest Signa gel is suitable for impedance matching when using multiple TCREs to obtain high-resolution EEG recordings.
This document provides an overview of an artificial retina using thin film transistor technology. It discusses diseases like age-related macular degeneration that could be treated with a retinal implant. Two types of implants are described - epiretinal implants placed on the retinal surface and subretinal implants placed between retinal layers. The artificial retina would use phototransistors integrated on a flexible substrate to convert light images to electrical signals and stimulate remaining retinal cells. Wireless power transmission through inductive coupling would allow continuous operation. While promising for restoring vision, challenges remain in biocompatibility, power efficiency, and image resolution.
This study analyzed optimization of wireless power transfer using a half-bridge flyback converter. The researchers designed a protection circuit to maintain the resonant frequency as the load changed. Experiments showed wireless power transfer of over 3.4W and 61% efficiency to a variable LED load. Adding the protection circuit produced more stable output than without it by preventing changes in resonant frequency from load variations.
Trends in VLSI circuit in 2020 - International Journal of VLSI design & Commu...VLSICS Design
International Journal of VLSI design & Communication Systems (VLSICS) is a bi monthly open access peer-reviewed journal that publishes articles which contribute new results in all areas of VLSI Design & Communications. The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on advanced VLSI Design & communication concepts and establishing new collaborations in these areas.
Recharging Mechanism of Wireless Sensor Network: A Surveyijsrd.com
WSN have been extensively researched during recent years helping in diverse employment of sensor networks in various systems and applications. One of the key challenges that preclude the sustained operation of these networks is their limited energy resources. One of the most critical limiting factors for a Wireless Sensor Network (WSN) is its battery life. Therefore, a very desirable feature of WSN would be its rechargability to remain operational over longer period of times. The wireless sensor node, being a limited form factor device, can only be equipped with a limited power source. In this paper, we have presented several existing techniques for recharging a sensor node in wireless sensor networks.
Wireless sensor nodes are usually deployed in not easily accessible places to provide solution to a wide
range of application such as environmental, medical and structural monitoring. They are spatially
distributed and as a result are usually powered from batteries. Due to the limitation in providing power
with batteries, which must be manually replaced when they are depleted, and location constraints in
wireless sensor network causes a major setback on performance and lifetime of WSNs. This difficulty in
battery replacement and cost led to a growing interest in energy harvesting. The current practice in energy
harvesting for sensor networks is based on practical and simulation approach. The evaluation and
validation of the WSN systems is mostly done using simulation and practical implementation. Simulation is
widely used especially for its great advantage in evaluating network systems. Its disadvantages such as the
long time taken to simulate and not being economical as it implements data without proper analysis of all
that is involved ,wasting useful resources cannot be ignored. In most times, the energy scavenged is directly
wired to the sensor nodes. We, therefore, argue that simulation – based and practical implementation of
WSN energy harvesting system should be further strengthened through mathematical analysis and design
procedures. In this work, we designed and modeled the energy harvesting system for wireless sensor nodes
based on the input and output parameters of the energy sources and sensor nodes. We also introduced the
use of supercapacitor as buffer and intermittent source for the sensor node. The model was further tested in
a Matlab environment, and found to yield a very good approach for system design.
Design and Optimization of Inductively Coupled Spiral Square Coils for Bio-Im...IJECEIAES
Due to the development of biomedical microsystems technologies, the use of wireless power transfer systems in biomedical application has become very largely used for powering the implanted devices. The wireless power transfer by inductive resonance coupling link, is a technic for powering implantable medical devices (IMDs) between the external and implanted circuits. In this paper we describe the design of an inductive resonance coupling link using for powering small bio-implanted devices such as implantable bio-microsystem, peacemaker and cochlear implants. We present the reduced design and an optimization of small size obtained spiral coils of a 9.5 mm2 implantable device with an operating frequency of 13.56 MHz according to the industrial scientific-medical (ISM). The model of the inductive coupling link based on spiral square coils design is developed using the theoretical analysis and optimization geometry of an inductive link. For a mutual distance between the two coils at 10mm, the power transfer efficiency is about 79% with , coupling coefficient of 0.075 and a mutual inductance value of 2µH. In comparison with previous works, the results obtained in this work showed better performance such as the weak inter coils distance, the hight efficiency power transfer and geometry.
This document describes a study that tested the effectiveness of using Signa gel with tripolar concentric ring electrodes (TCREs) to record electroencephalography (EEG) signals from the brain. TCREs are a type of electrode that can help reduce noise in EEG recordings compared to conventional disc electrodes. The study found that 10 mm diameter TCREs attached with Signa gel were able to clearly detect alpha wave brain activity, but smaller 6 mm and 4 mm TCREs were less consistent, possibly due to noisy connections to the recording interface. The results suggest Signa gel is suitable for impedance matching when using multiple TCREs to obtain high-resolution EEG recordings.
This document provides an overview of an artificial retina using thin film transistor technology. It discusses diseases like age-related macular degeneration that could be treated with a retinal implant. Two types of implants are described - epiretinal implants placed on the retinal surface and subretinal implants placed between retinal layers. The artificial retina would use phototransistors integrated on a flexible substrate to convert light images to electrical signals and stimulate remaining retinal cells. Wireless power transmission through inductive coupling would allow continuous operation. While promising for restoring vision, challenges remain in biocompatibility, power efficiency, and image resolution.
This study analyzed optimization of wireless power transfer using a half-bridge flyback converter. The researchers designed a protection circuit to maintain the resonant frequency as the load changed. Experiments showed wireless power transfer of over 3.4W and 61% efficiency to a variable LED load. Adding the protection circuit produced more stable output than without it by preventing changes in resonant frequency from load variations.
Trends in VLSI circuit in 2020 - International Journal of VLSI design & Commu...VLSICS Design
International Journal of VLSI design & Communication Systems (VLSICS) is a bi monthly open access peer-reviewed journal that publishes articles which contribute new results in all areas of VLSI Design & Communications. The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on advanced VLSI Design & communication concepts and establishing new collaborations in these areas.
Recharging Mechanism of Wireless Sensor Network: A Surveyijsrd.com
WSN have been extensively researched during recent years helping in diverse employment of sensor networks in various systems and applications. One of the key challenges that preclude the sustained operation of these networks is their limited energy resources. One of the most critical limiting factors for a Wireless Sensor Network (WSN) is its battery life. Therefore, a very desirable feature of WSN would be its rechargability to remain operational over longer period of times. The wireless sensor node, being a limited form factor device, can only be equipped with a limited power source. In this paper, we have presented several existing techniques for recharging a sensor node in wireless sensor networks.
Artificial Neural Network for Solar Photovoltaic System Modeling and Simulationijtsrd
This paper presented neural network based maximum power point tracking on the design of photovoltaic power input to a DC DC boot converter to the load. Simulink model of photovoltaic array tested the neural network with different temperature and irradiance for maximum power point of a photovoltaic system. DC DC boot converter is used in load when an average output voltage is stable required which can be lower than the input voltage. At the end, the different temperature and irradiance of the data collected from the photovoltaic array system is used to train the neutral network and output efficiency of the designed DC DC boot converter with MPPT control strategy is accepted the maximum power amount to show the result voltage, current and power output for each different have been presented. And also demonstrated that the neural network based MPPT tracking require less time and more accurate results than the other algorithm based MPPT. Myint Thuzar | Cho Hnin Moh Moh Aung "Artificial Neural Network for Solar Photovoltaic System Modeling and Simulation" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd27867.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/27867/artificial-neural-network-for-solar-photovoltaic-system-modeling-and-simulation/myint-thuzar
Energy efficient chaotic whale optimization technique for data gathering in w...IJECEIAES
The document presents a new technique called chaotic whale metaheuristic energy optimized data gathering (CWMEODG) to improve energy efficient data gathering in wireless sensor networks with minimal energy consumption, packet loss, and delay. The CWMEODG technique uses chaotic whale optimization and selects sensor nodes with higher residual energy as the "current best" to transmit data packets to the sink node. Simulation results showed that the CWMEODG technique improves data gathering performance and network lifetime more than existing state-of-the-art methods.
A STUDY OF POWER SAVING TECHNIQUE IN WIRELESS NETWORKScscpconf
This document discusses various power saving techniques in wireless networks. It begins by describing the typical workload profile of a wireless sensor network and discusses an energy efficient heterogeneous multiprocessor sensor node architecture that uses low-power and high-power processors depending on the workload. It also discusses dynamic voltage scaling and ultra-low power medium access control protocols for both wireless sensor networks and cellular networks. Finally, it discusses improvements to power amplifiers in base stations and RF transceivers for wireless sensor nodes to reduce power consumption.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
The document summarizes research on neural engineering related to cochlear implants and intracortical microelectrodes. It discusses:
1) Cochlear implant research involving developing a method to fit implants using stapedius electromyography recordings in rats.
2) Chronic neural interfacing research using intracortical microelectrodes to record brain activity, the challenges of long-term recordings due to tissue encapsulation, and methods explored to address this like enzyme-aided electrode insertion.
3) The quantification of recording performance over time and correlations with electrode impedance.
IRJET- Ultrafast Photoconductive Antenna with Dual-BandIRJET Journal
This document presents a design for a dual-band ultrafast photoconductive antenna. The antenna uses a single
photoconductive switch (PCS) that can simultaneously emit terahertz radiation in the low THz region (around 300 GHz) and
in the low frequency range between 10-20 GHz. The dual-band antenna consists of a square spiral antenna connected to
the PCS for the higher 300 GHz band and a dipole antenna connected to the PCS for the lower 10-20 GHz band. The
antenna was experimentally characterized in terms of average power, polarization, and power spectral density. The low
frequency band was chosen because it has good atmospheric transmission properties beneficial for wireless
communications and radar
This project aims to develop stable electrical contact between cortical organoids and embedded flexible electrodes. A 3D-printed tube insert was designed to promote intimate contact between organoids and electrodes by providing an inclined space for organoids to naturally attach to electrode surfaces. Impedance measurements were taken of electrode contacts to identify functional recording sites. Initial experiments culturing organoids on electrodes used elevated dishes or inclined PDMS pieces to stabilize the organoid-electrode setup. Future steps involve demonstrating long-term organoid survival when embedded with electrodes and recording electrical activity from organoid neurons over time.
A transient current based micro grid connected power system protection scheme...IJECEIAES
Micro-grids comprise Distributed Energy Resources (DER’s) with low voltage distribution networks having controllable loads those can operate with different voltage levels are connected to the micro-grid and operated in grid mode or islanding mode in a coordinated way of control. DER’s provides clear environment-economical benefits for society and consumer utilities. But their development poses great technical challenges mainly protection of main and micro grid. Protection scheme must have to respond to both the main grid and micro-grid faults. If the fault is occurs on main grid, the response must isolate the DER’s from the main grid rapidly to protect the system loads. If the fault ocuurs within the micro-grid, the protection scheme must coordinate and isolates the least priority possible part of the grid to eliminate the fault. In order to deal with the bidirectional energy flow due to large numbers of micro sources new protection schemes are required. The system is simulated using MATLAB Wavelet Tool box and Wavelet based Multi-resolution Analysis is considered. Wavelet based Multi-resolution Analysis is used for detection, discrimination and location of faults on transmission network. This paper is discussed a transient current based micro-grid connected power system protection scheme using Wavelet Approach described on wavelet detailed-coefficients of Mother Biorthogonal 1.5 wavelet. The proposed algorithm is tested in micro-grid connected power systems environment and proved for the detection, discrimination and location of faults which is almost independent of fault impedance, fault inception angle (FIA) and fault distance of feeder line.
This document provides an overview of energy harvesting technologies for sustainable wireless sensor networks. It discusses how wireless sensor networks (WSNs) are being used in applications like structural health monitoring and battlefield surveillance. WSNs allow for distributed sensing and processing but face challenges around limited energy resources. The document reviews different energy harvesting technologies that could provide sustainable power sources for sensor nodes, like solar, thermal, and kinetic energy harvesting. It examines how these technologies work and their potential to enable long-term operation of energy-constrained wireless sensor networks.
Dominant mode resonant frequency of circular microstrip antennas with and wit...IAEME Publication
This document summarizes the design and analysis of circular microstrip antennas. It discusses the calculation of the resonant frequency of circular microstrip antennas with and without air gaps between the patch and substrate. An improved analytical model is presented to calculate the resonant frequency for any antenna diameter and substrate properties. The model introduces an effective dielectric constant term to account for effects of the equivalent dielectric constant of the medium below the patch and the dynamic dielectric constant. Experimental results from previous studies are shown to validate the theoretical model for antennas with different dimensions and air gap heights.
This document describes a novel design method for a 3 to 8 decoder circuit using a hybrid single electron transistor (SET)-CMOS approach. It begins by providing background on SETs and their advantages over traditional CMOS at nanoscale, including ultra-low power dissipation. It then presents the design and simulation of basic logic gates like inverters and XOR gates using a hybrid CMOS-SET approach. Finally, it describes the design and simulation of a 3 to 8 decoder circuit implemented using the hybrid logic gates. The simulation results show the decoder circuit operates correctly at room temperature. The hybrid CMOS-SET approach allows leveraging the benefits of both technologies for low-power nanoscale circuit design.
Simulation of AlGaN/Si and InN/Si ELECTRIC –DEVICESijrap
In this work, efficient solar-blind metal-semiconductor photodetectors grown on Si (111) by
molecular beam epitaxy are reported. Growth details are described,the comparison enters the
properties electric of InN/Si and AlGaN/Si photodectors with 0.2 μm of AlGaN and InN layers.
Modeling and simulation were performed by using ATLAS-TCAD simulator. Energy band
diagram, doping profile, conduction current density,I-V caracteristic , internal potential and
electric field were performed.
Determination of Spectral Power Distribution and Spectral Mismatch Factor for...IJERA Editor
The present research aimed to investigate some lighting characteristics of six commercial compact fluorescent lamps (CFLs). The lighting characteristics such as spectral power distributions (SPDs), and spectral mismatch correction factor (SCF) to human response eye curve V(λ) have important roles on visual health effects of the lamps. A set up based on National Institute of standards of Egypt (NIS) Spectroradiometer ocean optics HR 2000 with uncertainty 4.7% and the photometric bench has been used for measuring the spectral power distribution of the lamps to determine the spectral mismatch correction factor. Calculations of comparative analysis have been done for spectral mismatch correction factor (SCF) to human response curve V (λ). The spectral power distributions (SPDs) diagrams for the commercial compact lamps (CFLs) showed typical CFLs response, with a few narrow spectral peaks. The histogram for comparison of spectral mismatch factor shows the spectral mismatch factor for each CFL lamp and the degree of perfectly spectral matching with human response eye curve V (λ). Data analysis was performed and uncertainty model includes all parameters accompanied with the measurements are calculated.
CLASS D POWER AMPLIFIER FOR MEDICAL APPLICATIONieijjournal
This document describes the design of a 2.4 GHz class D power amplifier for medical applications using 0.18um CMOS technology. A two-stage class D power amplifier was designed that can transmit 15dBm of output power to a 50Ω load with 50% power added efficiency and total power consumption of 90.4 mW. Simulation results showed the amplifier was stable with an S11 of less than -10 dB and meets requirements for wireless medical sensor networks. The goal was to minimize trade-offs between performance, cost and power consumption for healthcare applications.
This document summarizes an approach to embedding a human brain with smart devices using depreciated brain-computer interface (BCI) technology. It discusses how BCI systems work by acquiring EEG signals from the brain, preprocessing the signals, classifying them, and using them to control external applications. Specifically, it proposes controlling a tablet through a 1-channel EEG amplifier and non-invasive electrode placement. The document outlines the basic components and applications of BCI systems and describes implementing a basic prototype to test controlling a media player on a tablet using EEG signals processed in MATLAB.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Design and simulation of a tunable frequency microstrip patch antennaeSAT Journals
Abstract This paper presents an evaluation of frequency reconfigurable patch antennas for X-band, using PIN diode as a switch. A pin diode is incorporated in the slot etched on rectangular patch antenna. The frequency band selectivity can be achieved by controlling the state of switch inserted in the antenna. We are using IE3D simulation software for designing and analysis. We have discussed and analyzed the performance of unslotted Rectangular Microstrip patch antenna and slotted rectangular patch antenna with PIN diode in ON and OFF states. Keyword: Microstrip Antenna, Return Loss, Radiation pattern, IE3D.
AN ELECTRICAL IMPEDANCE TOMOGRAPHY SYSTEM FOR THYROID GLAND WITH A TINY ELECT...ijbesjournal
Electrical impedance Tomography (EIT) is a non-invasive imaging technique based on measuring of the
electrical conductivity and capacitance of abnormal and normal human tissues. The present work aims to
develop an EIT imaging system for imaging thyroid gland. Patients with thyroid nodules were eligible for
the study. The study was conducted on two groups of participants: control group consists of 20 normal
female cases and experimental consists of 20 goiter female patients. The thyroid nodule location, size, and
type measured by ultrasound. Thyroid gland conductivity and permittivity were recorded using EIT. The
impedance measurement is done through the applying of two probes: one probe to the neck region
(scanning probe) and the rest region (reference probe) with electrolytic gel for each probe, then the system
software proceeds to reconstruct the image and calculate the electrical impedance of the thyroid gland on
a personal computer which acts as an output display and storage for case information. The thyroid
scanning probe has 64 electrodes embedded on a small space (30 mm diameter and 50 mm height) inside
of the probe. Multifrequency impedance measurements are typically made by applying an electric current
to a target mass by using of the scanning probe and measuring the developed voltage. The present EIT
system provides real- time visualization of the spatial distribution of the electrical properties of the thyroid
tissue. Images obtained from the bioimpedance (BI) were compared to images obtained from the
ultrasound imaging, results showed great similarity between the two diagnostic images. Tumor tissue has
higher resistance and capacitance value than that of normal thyroid gland.
An electronic measurement system using an interdigitated capacitive sensor has been developed to more accurately measure spinal fusion progress by detecting cartilage formation, allowing earlier rehabilitation. The sensor will be mounted on a spinal plate and connected to circuitry to measure its changing capacitance during plate bending. The circuitry design includes stages for capacitance measurement, analog to digital conversion, and wireless data transmission. The objective is to complete the first capacitance measurement stage. Testing of different circuits found the Low-Z Amplifier accurately measures capacitances in the picofarad range needed. Preliminary work has been done on later stages using an Arduino, with challenges including wireless transmission through body and circuit miniaturization.
Artificial Neural Network for Solar Photovoltaic System Modeling and Simulationijtsrd
This paper presented neural network based maximum power point tracking on the design of photovoltaic power input to a DC DC boot converter to the load. Simulink model of photovoltaic array tested the neural network with different temperature and irradiance for maximum power point of a photovoltaic system. DC DC boot converter is used in load when an average output voltage is stable required which can be lower than the input voltage. At the end, the different temperature and irradiance of the data collected from the photovoltaic array system is used to train the neutral network and output efficiency of the designed DC DC boot converter with MPPT control strategy is accepted the maximum power amount to show the result voltage, current and power output for each different have been presented. And also demonstrated that the neural network based MPPT tracking require less time and more accurate results than the other algorithm based MPPT. Myint Thuzar | Cho Hnin Moh Moh Aung "Artificial Neural Network for Solar Photovoltaic System Modeling and Simulation" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd27867.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/27867/artificial-neural-network-for-solar-photovoltaic-system-modeling-and-simulation/myint-thuzar
Energy efficient chaotic whale optimization technique for data gathering in w...IJECEIAES
The document presents a new technique called chaotic whale metaheuristic energy optimized data gathering (CWMEODG) to improve energy efficient data gathering in wireless sensor networks with minimal energy consumption, packet loss, and delay. The CWMEODG technique uses chaotic whale optimization and selects sensor nodes with higher residual energy as the "current best" to transmit data packets to the sink node. Simulation results showed that the CWMEODG technique improves data gathering performance and network lifetime more than existing state-of-the-art methods.
A STUDY OF POWER SAVING TECHNIQUE IN WIRELESS NETWORKScscpconf
This document discusses various power saving techniques in wireless networks. It begins by describing the typical workload profile of a wireless sensor network and discusses an energy efficient heterogeneous multiprocessor sensor node architecture that uses low-power and high-power processors depending on the workload. It also discusses dynamic voltage scaling and ultra-low power medium access control protocols for both wireless sensor networks and cellular networks. Finally, it discusses improvements to power amplifiers in base stations and RF transceivers for wireless sensor nodes to reduce power consumption.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
The document summarizes research on neural engineering related to cochlear implants and intracortical microelectrodes. It discusses:
1) Cochlear implant research involving developing a method to fit implants using stapedius electromyography recordings in rats.
2) Chronic neural interfacing research using intracortical microelectrodes to record brain activity, the challenges of long-term recordings due to tissue encapsulation, and methods explored to address this like enzyme-aided electrode insertion.
3) The quantification of recording performance over time and correlations with electrode impedance.
IRJET- Ultrafast Photoconductive Antenna with Dual-BandIRJET Journal
This document presents a design for a dual-band ultrafast photoconductive antenna. The antenna uses a single
photoconductive switch (PCS) that can simultaneously emit terahertz radiation in the low THz region (around 300 GHz) and
in the low frequency range between 10-20 GHz. The dual-band antenna consists of a square spiral antenna connected to
the PCS for the higher 300 GHz band and a dipole antenna connected to the PCS for the lower 10-20 GHz band. The
antenna was experimentally characterized in terms of average power, polarization, and power spectral density. The low
frequency band was chosen because it has good atmospheric transmission properties beneficial for wireless
communications and radar
This project aims to develop stable electrical contact between cortical organoids and embedded flexible electrodes. A 3D-printed tube insert was designed to promote intimate contact between organoids and electrodes by providing an inclined space for organoids to naturally attach to electrode surfaces. Impedance measurements were taken of electrode contacts to identify functional recording sites. Initial experiments culturing organoids on electrodes used elevated dishes or inclined PDMS pieces to stabilize the organoid-electrode setup. Future steps involve demonstrating long-term organoid survival when embedded with electrodes and recording electrical activity from organoid neurons over time.
A transient current based micro grid connected power system protection scheme...IJECEIAES
Micro-grids comprise Distributed Energy Resources (DER’s) with low voltage distribution networks having controllable loads those can operate with different voltage levels are connected to the micro-grid and operated in grid mode or islanding mode in a coordinated way of control. DER’s provides clear environment-economical benefits for society and consumer utilities. But their development poses great technical challenges mainly protection of main and micro grid. Protection scheme must have to respond to both the main grid and micro-grid faults. If the fault is occurs on main grid, the response must isolate the DER’s from the main grid rapidly to protect the system loads. If the fault ocuurs within the micro-grid, the protection scheme must coordinate and isolates the least priority possible part of the grid to eliminate the fault. In order to deal with the bidirectional energy flow due to large numbers of micro sources new protection schemes are required. The system is simulated using MATLAB Wavelet Tool box and Wavelet based Multi-resolution Analysis is considered. Wavelet based Multi-resolution Analysis is used for detection, discrimination and location of faults on transmission network. This paper is discussed a transient current based micro-grid connected power system protection scheme using Wavelet Approach described on wavelet detailed-coefficients of Mother Biorthogonal 1.5 wavelet. The proposed algorithm is tested in micro-grid connected power systems environment and proved for the detection, discrimination and location of faults which is almost independent of fault impedance, fault inception angle (FIA) and fault distance of feeder line.
This document provides an overview of energy harvesting technologies for sustainable wireless sensor networks. It discusses how wireless sensor networks (WSNs) are being used in applications like structural health monitoring and battlefield surveillance. WSNs allow for distributed sensing and processing but face challenges around limited energy resources. The document reviews different energy harvesting technologies that could provide sustainable power sources for sensor nodes, like solar, thermal, and kinetic energy harvesting. It examines how these technologies work and their potential to enable long-term operation of energy-constrained wireless sensor networks.
Dominant mode resonant frequency of circular microstrip antennas with and wit...IAEME Publication
This document summarizes the design and analysis of circular microstrip antennas. It discusses the calculation of the resonant frequency of circular microstrip antennas with and without air gaps between the patch and substrate. An improved analytical model is presented to calculate the resonant frequency for any antenna diameter and substrate properties. The model introduces an effective dielectric constant term to account for effects of the equivalent dielectric constant of the medium below the patch and the dynamic dielectric constant. Experimental results from previous studies are shown to validate the theoretical model for antennas with different dimensions and air gap heights.
This document describes a novel design method for a 3 to 8 decoder circuit using a hybrid single electron transistor (SET)-CMOS approach. It begins by providing background on SETs and their advantages over traditional CMOS at nanoscale, including ultra-low power dissipation. It then presents the design and simulation of basic logic gates like inverters and XOR gates using a hybrid CMOS-SET approach. Finally, it describes the design and simulation of a 3 to 8 decoder circuit implemented using the hybrid logic gates. The simulation results show the decoder circuit operates correctly at room temperature. The hybrid CMOS-SET approach allows leveraging the benefits of both technologies for low-power nanoscale circuit design.
Simulation of AlGaN/Si and InN/Si ELECTRIC –DEVICESijrap
In this work, efficient solar-blind metal-semiconductor photodetectors grown on Si (111) by
molecular beam epitaxy are reported. Growth details are described,the comparison enters the
properties electric of InN/Si and AlGaN/Si photodectors with 0.2 μm of AlGaN and InN layers.
Modeling and simulation were performed by using ATLAS-TCAD simulator. Energy band
diagram, doping profile, conduction current density,I-V caracteristic , internal potential and
electric field were performed.
Determination of Spectral Power Distribution and Spectral Mismatch Factor for...IJERA Editor
The present research aimed to investigate some lighting characteristics of six commercial compact fluorescent lamps (CFLs). The lighting characteristics such as spectral power distributions (SPDs), and spectral mismatch correction factor (SCF) to human response eye curve V(λ) have important roles on visual health effects of the lamps. A set up based on National Institute of standards of Egypt (NIS) Spectroradiometer ocean optics HR 2000 with uncertainty 4.7% and the photometric bench has been used for measuring the spectral power distribution of the lamps to determine the spectral mismatch correction factor. Calculations of comparative analysis have been done for spectral mismatch correction factor (SCF) to human response curve V (λ). The spectral power distributions (SPDs) diagrams for the commercial compact lamps (CFLs) showed typical CFLs response, with a few narrow spectral peaks. The histogram for comparison of spectral mismatch factor shows the spectral mismatch factor for each CFL lamp and the degree of perfectly spectral matching with human response eye curve V (λ). Data analysis was performed and uncertainty model includes all parameters accompanied with the measurements are calculated.
CLASS D POWER AMPLIFIER FOR MEDICAL APPLICATIONieijjournal
This document describes the design of a 2.4 GHz class D power amplifier for medical applications using 0.18um CMOS technology. A two-stage class D power amplifier was designed that can transmit 15dBm of output power to a 50Ω load with 50% power added efficiency and total power consumption of 90.4 mW. Simulation results showed the amplifier was stable with an S11 of less than -10 dB and meets requirements for wireless medical sensor networks. The goal was to minimize trade-offs between performance, cost and power consumption for healthcare applications.
This document summarizes an approach to embedding a human brain with smart devices using depreciated brain-computer interface (BCI) technology. It discusses how BCI systems work by acquiring EEG signals from the brain, preprocessing the signals, classifying them, and using them to control external applications. Specifically, it proposes controlling a tablet through a 1-channel EEG amplifier and non-invasive electrode placement. The document outlines the basic components and applications of BCI systems and describes implementing a basic prototype to test controlling a media player on a tablet using EEG signals processed in MATLAB.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Design and simulation of a tunable frequency microstrip patch antennaeSAT Journals
Abstract This paper presents an evaluation of frequency reconfigurable patch antennas for X-band, using PIN diode as a switch. A pin diode is incorporated in the slot etched on rectangular patch antenna. The frequency band selectivity can be achieved by controlling the state of switch inserted in the antenna. We are using IE3D simulation software for designing and analysis. We have discussed and analyzed the performance of unslotted Rectangular Microstrip patch antenna and slotted rectangular patch antenna with PIN diode in ON and OFF states. Keyword: Microstrip Antenna, Return Loss, Radiation pattern, IE3D.
AN ELECTRICAL IMPEDANCE TOMOGRAPHY SYSTEM FOR THYROID GLAND WITH A TINY ELECT...ijbesjournal
Electrical impedance Tomography (EIT) is a non-invasive imaging technique based on measuring of the
electrical conductivity and capacitance of abnormal and normal human tissues. The present work aims to
develop an EIT imaging system for imaging thyroid gland. Patients with thyroid nodules were eligible for
the study. The study was conducted on two groups of participants: control group consists of 20 normal
female cases and experimental consists of 20 goiter female patients. The thyroid nodule location, size, and
type measured by ultrasound. Thyroid gland conductivity and permittivity were recorded using EIT. The
impedance measurement is done through the applying of two probes: one probe to the neck region
(scanning probe) and the rest region (reference probe) with electrolytic gel for each probe, then the system
software proceeds to reconstruct the image and calculate the electrical impedance of the thyroid gland on
a personal computer which acts as an output display and storage for case information. The thyroid
scanning probe has 64 electrodes embedded on a small space (30 mm diameter and 50 mm height) inside
of the probe. Multifrequency impedance measurements are typically made by applying an electric current
to a target mass by using of the scanning probe and measuring the developed voltage. The present EIT
system provides real- time visualization of the spatial distribution of the electrical properties of the thyroid
tissue. Images obtained from the bioimpedance (BI) were compared to images obtained from the
ultrasound imaging, results showed great similarity between the two diagnostic images. Tumor tissue has
higher resistance and capacitance value than that of normal thyroid gland.
An electronic measurement system using an interdigitated capacitive sensor has been developed to more accurately measure spinal fusion progress by detecting cartilage formation, allowing earlier rehabilitation. The sensor will be mounted on a spinal plate and connected to circuitry to measure its changing capacitance during plate bending. The circuitry design includes stages for capacitance measurement, analog to digital conversion, and wireless data transmission. The objective is to complete the first capacitance measurement stage. Testing of different circuits found the Low-Z Amplifier accurately measures capacitances in the picofarad range needed. Preliminary work has been done on later stages using an Arduino, with challenges including wireless transmission through body and circuit miniaturization.
This document describes a wireless power transfer system using thin film resonant cells for powering implanted and worn medical devices. The system uses resonant magnetic coupling between a transmitter coil placed around the waist and receiver coils near the implanted/worn devices. The thin film cells are made of flexible copper tape and polymer layers to be lightweight and conform to the body. Experimental results show the system can efficiently transfer power over longer ranges than existing magnetic coupling methods, with 40.2% efficiency achieved at a 20cm distance.
A Novel Approach for Measuring Electrical Impedance Tomography for Local Tiss...CSCJournals
This paper proposes a novel approach for measuring Electrical Impedance Tomography (EIT) of a living tissue in a human body. EIT is a non-invasive technique to measure two or three-dimensional impedance for medical diagnosis involving several diseases. To measure the impedance value electrodes are connected to the skin of the patient and an image of the conductivity or permittivity of living tissue is deduced from surface electrodes. The determination of local impedance parameters can be carried out using an equivalent circuit model. However, the estimation of inner tissue impedance distribution using impedance measurements on a global tissue from various directions is an inverse problem. Hence it is necessary to solve the inverse problem of calculating mathematical values for current and potential from conducting surfaces. This paper proposes a novel algorithm that can be successfully used for estimating parameters. The proposed novel hybrid model is a combination of an artificial intelligence based gradient free optimization technique and numerical integration. This ameliorates the achievement of spatial resolution of equivalent circuit model to the closest accuracy. We address the issue of initial parameter estimation and spatial resolution accuracy of an electrode structure by using an arrangement called “divided electrode” for measurement of bio-impedance in a cross section of a local tissue.
This document describes a study using microwave imaging to detect brain strokes. Researchers used an anatomically realistic numerical head phantom with an inserted simulated hemorrhagic stroke. Microwave signals were used to estimate backscattered signals from the phantom. The Born iterative method was then applied to the signals to reconstruct an image of the phantom and detect the inserted stroke based on differences in dielectric properties between healthy and stroke-affected tissues. The study aims to more accurately model attenuation and reflections in the head compared to previous works using simpler phantoms. Reconstructed images using 850 MHz signals clearly detected the inserted stroke region.
Efficient wireless power transmission to remote the sensor in restenosis coro...nooriasukmaningtyas
In this study, the researchers have proposed an alternative technique for designing an asymmetric 4 coil-resonance coupling module based on the series-to-parallel topology at 27 MHz industrial scientific medical (ISM) band to avoid the tissue damage, for the constant monitoring of the in-stent restenosis coronary artery. This design consisted of 2 components, i.e., the external part that included 3 planar coils that were placed outside the body and an internal helical coil (stent) that was implanted into the coronary artery in the human tissue. This technique considered the output power and the transfer efficiency of the overall system, coil geometry like the number of coils per turn, and coil size. The results indicated that this design showed an 82% efficiency in the air if the transmission distance was maintained as 20 mm, which allowed the wireless power supply system to monitor the pressure within the coronary artery when the implanted load resistance was 400 Ω.
This document summarizes techniques for harvesting energy for implantable biosensors. It discusses kinetic, thermoelectric, and inductive powering methods. Kinetic harvesters convert body motion to electricity using electromagnetic, electrostatic, or piezoelectric transducers, but have limitations for small implants. Thermoelectric harvesters use temperature differences to generate voltage via the Seebeck effect but require large areas to produce sufficient power. Inductive links can wirelessly power implants through tissues and enable data communication. High frequency inductive links are also described.
Day by day the scope & use of the electronics concepts in bio-medical field is increasing step by step. In this paper the review of newly developed concepts is done for the monitoring of the ECG signal. This paper also reviews a power and area efficient electrocardiogram (ECG) acquisition and signal processing application sensor node. Further the study of IoT frame work for ECG monitoring has been carried out. Ms. Dhanashri Yamagekar | Dr. Pradip Bhaskar"Real time ECG Monitoring: A Review" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-1 , December 2017, URL: http://www.ijtsrd.com/papers/ijtsrd7065.pdf http://www.ijtsrd.com/engineering/electronics-and-communication-engineering/7065/real-time-ecg-monitoring-a-review/ms-dhanashri-yamagekar
IRJET- Non-Invasive Blood Glucose Measurement Depending on the Blood Dielectr...IRJET Journal
This document describes a proposed non-invasive method for measuring blood glucose concentration using ultra-wideband technology. It discusses how blood glucose levels affect the dielectric properties of blood, specifically decreasing permittivity as glucose concentration increases. An experiment is described using an open-ended coaxial probe and vector network analyzer to measure the dielectric properties of blood samples with varying glucose levels. The results show an inverse relationship between permittivity and glucose concentration. This relationship could allow calculating glucose levels from dielectric measurements in a non-invasive manner using a single UWB transceiver attached to blood vessels.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
Marom Bikson speaks at the BrainSTIM2015 - Targeting transcranial Electrical Stimulation (tES) using EEG. Includes how to use EEG to inform transcranial Direct Current Stimulation (tDCS) montages. And critical pitfalls in concurrent recording. Stay tuned for our upcoming paper on reciprocity.
The complete video can be found here: https://www.youtube.com/watch?v=yYmDQB7qSCE
The first publication on the topic can be found here http://neuralengr.com/wp-content/uploads/2016/05/2016-Cancelli-A-simple-method.pdf
Related technology can be found here http://soterixmedical.com/research/monitoring/eeg
This document discusses using artificial neural networks (ANNs) and statistical techniques to classify partial discharge (PD) defects within cross-linked polyethylene (XLPE) medium voltage cables. PD measurements were taken from six cables with different defects and voltages. Statistical features were extracted from the 3D PD patterns to form the input for various ANNs for classification. 72 different ANN structures were analyzed to determine the most effective and optimal classification technique, based on metrics like mean square error and accuracy. The proposed approach achieved high recognition rates for identifying different types of PD defects within XLPE cables.
Implementation of Radon Transformation for Electrical Impedance Tomography (E...ijistjournal
Radon Transformation is generally used to construct optical image (like CT image) from the projection data in biomedical imaging. In this paper, the concept of Radon Transformation is implemented to reconstruct Electrical Impedance Topographic Image (conductivity or resistivity distribution) of a circular subject. A parallel resistance model of a subject is proposed for Electrical Impedance Topography(EIT) or Magnetic Induction Tomography(MIT). A circular subject with embedded circular objects is segmented into equal width slices from different angles. For each angle, Conductance and Conductivity of each slice is calculated and stored in an array. A back projection method is used to generate a two-dimensional image from one-dimensional projections. As a back projection method, Inverse Radon Transformation is applied on the calculated conductance and conductivity to reconstruct two dimensional images. These images are compared to the target image. In the time of image reconstruction, different filters are used and these images are compared with each other and target image.
Implementation of Radon Transformation for Electrical Impedance Tomography (EIT)ijistjournal
Radon Transformation is generally used to construct optical image (like CT image) from the projection data in biomedical imaging. In this paper, the concept of Radon Transformation is implemented to reconstruct Electrical Impedance Topographic Image (conductivity or resistivity distribution) of a circular subject. A parallel resistance model of a subject is proposed for Electrical Impedance Topography(EIT) or Magnetic Induction Tomography(MIT). A circular subject with embedded circular objects is segmented into equal width slices from different angles. For each angle, Conductance and Conductivity of each slice is calculated and stored in an array. A back projection method is used to generate a two-dimensional image from one-dimensional projections. As a back projection method, Inverse Radon Transformation is applied on the calculated conductance and conductivity to reconstruct two dimensional images. These images are compared to the target image. In the time of image reconstruction, different filters are used and these images are compared with each other and target image.
A nonlinearities inverse distance weighting spatial interpolation approach ap...IJECEIAES
Spatial interpolation of a surface electromyography (sEMG) signal from a set of signals recorded from a multi-electrode array is a challenge in biomedical signal processing. Consequently, it could be useful to increase the electrodes' density in detecting the skeletal muscles' motor units under detection's vacancy. This paper used two types of spatial interpolation methods for estimation: Inverse distance weighted (IDW) and Kriging. Furthermore, a new technique is proposed using a modified nonlinearity formula based on IDW. A set of EMG signals recorded from the noninvasive multi-electrode grid from different types of subjects, sex, age, and type of muscles have been studied when muscles are under regular tension activity. A goodness of fit measure (R2) is used to evaluate the proposed technique. The interpolated signals are compared with the actual signals; the Goodness of fit measure's value is almost 99%, with a processing time of 100msec. The resulting technique is shown to be of high accuracy and matching of spatial interpolated signals to actual signals compared with IDW and Kriging techniques.
Compact X-Band LINAC structure design for KAERI-RTX-ISU Medical CyberKnife Pr...downtrev
This document describes the design of a compact X-band linear accelerator (linac) structure for a medical CyberKnife project conducted by Idaho State University, the Korean Atomic Energy Research Institute, and Radiation Technology eXcellence. The linac structure was designed using 2D SUPERFISH and 3D CST MICROWAVE STUDIO electromagnetic simulation programs. Key aspects of the design include optimizing a 15-cell π-mode standing wave linac structure and RF coupler to operate at 9.3 GHz, with the goal of achieving a compact, lightweight X-band linac that can be attached to a robotic arm for precise cancer treatment.
This document describes the design of a compact X-band linear accelerator (linac) structure for a medical CyberKnife project conducted by Idaho State University, the Korean Atomic Energy Research Institute, and Radiation Technology eXcellence. The linac structure was designed using 2D SUPERFISH and 3D CST MICROWAVE STUDIO electromagnetic simulation programs. Key aspects of the design include optimizing a 15-cell π-mode standing wave linac structure and RF coupler to operate at 9.3 GHz, with the goal of achieving a compact, lightweight X-band linac that can be attached to a robotic arm for precise cancer treatment.
1) A study explored using an electrode array and signal characteristics to select an optimal electrode pair for surface electromyography (sEMG), aiming to improve on existing electrode placement methods.
2) A 3x4 electrode array was placed over seven muscles on subjects. Nine bipolar electrode pairs were formed from each array.
3) sEMG parameters were calculated for each pair and evaluated based on repeatability across trials and comparison to a traditionally placed electrode pair, to determine if signal characteristics could help select a high quality electrode pair.
Similar to A-Virtual-Electrode-through-Summation-of-Time-Offset-Pulses (20)
1. Abstract—Retinal prostheses have been successful in eliciting
visual responses in implanted subjects. As these prostheses progress,
one of their major limitations is the need for increased resolution. As
an alternative to increasing the number of electrodes, virtual
electrodes may be used to increase the effective resolution of current
electrode arrays. This paper presents a virtual electrode technique
based upon time-offsets between stimuli. Two adjacent electrodes are
stimulated with identical pulses with too short of pulse widths to
activate a neuron, but one has a time offset of one pulse width. A
virtual electrode of twice the pulse width was then shown to appear in
the center, with a total width capable of activating a neuron. This can
be used in retinal implants by stimulating electrodes with pulse
widths short enough to not elicit responses in neurons, but with their
combined pulse width adequate to activate a neuron in between them.
Keywords—Electrical stimulation, Neuroprosthesis, Retinal
implant, Retinal Prosthesis, Virtual electrode.
I. INTRODUCTION
ETINAL prostheses seek to restore vision to those who
experience partial or total blindness due to retinitis
pigmentosa (RP) and age-related macular degeneration
(AMD). Although the diseases destroy the photoreceptors in
the eyes and significantly alter the composition of the retina,
they seem to leave behind a remnant of functional retinal
ganglion cells (RGCs) that are able to transmit visual signals
to the brain [1], [2]. Epi-retinal prostheses rely upon an array
of electrodes that are implanted onto the retina in order to
electrically stimulate these functional RGCs. Results have
been promising thus far, with successes in eliciting visual
responses in subjects that can be used to detect brightness,
read large letters, and detect directional movement [3], [4].
Unfortunately, one of the great challenges of these
prostheses is the selectivity of individual RGCs. Functional
vision would require the ability to systematically stimulate
small groups of neurons near an electrode. The Argus II,
currently the only FDA approved retinal prosthesis, has 60
electrodes, each 200 µm in diameter [5]. Considering that the
human eye contains 1.2-1.5 million RGCs, it becomes clear
that these 60 electrodes are inadequate on their own in
effectively stimulating specific, localized neurons [6]. Another
useful comparison is to television: High Definition is usually
defined as 1920x1080 pixels; that is over 2 million total
Isaac Cassar and Trevor Davis are undergraduate bioengineers at UCLA,
Los Angeles, CA 90095 USA (phone: 831-319-8483; e-mail:
icazzar@gmail.com, sdtrevordavis@gmail.com).
Yi-Kai Lo and Wentai Liu are with the University of California, Los
Angeles, CA 90095, USA (e-mail: yikai.lo@ucla.edu, wentai@ucla.edu).
The project is partially supported by grants from California Capital Equity
LLC, UC Laboratory Research Fee Program, and NSF ERC BMES.
pixels. Compare that to the 60 effective ‘pixels’ obtainable
from the Argus II and the problem becomes apparent.
The obvious solution is to create higher density electrode
arrays to increase the resultant image resolution, and these are
in development. However, with increased electrode density
comes with a variety of problems. High density dictates that
the electrodes should be small, but small electrodes run the
risk of having a high charge density that can kill adjacent
neurons [7]. In addition, there are a number of technological
obstacles to overcome such as data transfer, wireless power,
and stimulator design that must be accounted for [8]. Instead
of simply adding additional electrodes to increase resolution,
we propose to use stimulation parameters to create a unique
type of virtual electrode located between two existing
electrodes.
Virtual electrodes have been shown to appear between
adjacent electrodes when they are both stimulated
concurrently and have been able to elicit some neural
responses in cochlear implants [9], [10]. However, these
require a potential peak between the two electrodes, which
may or may not occur depending on the spacing of the two
electrodes and the amount of current injected. It also includes
the risk of additionally stimulating neurons directly above the
two stimulating electrodes, which is non-ideal. In our case, we
have created a virtual electrode through a similar, yet
fundamentally different approach. The theory behind our
virtual electrode is based upon the dependency of pulse width
on RGC activation. It has been shown that at sufficiently short
pulse widths retinal degenerated mice RGCs will not respond
to external stimulation [11]. Using this knowledge, the idea is
to stimulate two adjacent electrodes with a short enough pulse
width that they each fail to stimulate neurons directly above
them. However, through constructive interference a virtual
electrode of twice the pulse width should appear at the center
point between the two electrodes. This virtual electrode should
always appear, independent of electrode spacing, and should
prevent undesired RGC activation directly above the
stimulating electrodes.
II.MATERIALS AND METHODS
A.Recording Device
In order to mimic the operation of a real retinal implant, we
designed a three-axis voltage probe that is able to
quantitatively record the potential/electric field above a
stimulating electrode array (Fig. 1). The probe was used to
obtain various scans above the electrode surfaces from which
the pulse width, potential, and activating function of the
physical and virtual electrodes could be determined.
A Virtual Electrode through Summation of Time
Offset Pulses
Isaac Cassar, Trevor Davis, Yi-Kai Lo, Wentai Liu
R
World Academy of Science, Engineering and Technology
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2. Fig. 1 Schematic of experimental set up. Our system is composed of: [A] a three-axis motor stage, [B] a recording electrode, [C] a
microelectrode array placed in a glass with saline, [D] a ground, and [E] an ASIC stimulator
The probe used is a 10 µm diameter platinum
microelectrode (BASI, model: MF-2005), which is securely
mounted to an arm on a three-axis stage with a spatial
resolution of 5 µm. A custom LabView program was made to
control the stage motors and process the potential data
recorded from the probe via a data acquisition card (National
Instruments, model: NI USB-6259). The program has a
graphical user interface (GUI) that allows for automatic 3D
scanning above a designated region of the electrode array (Fig.
2). It also offers a variety of recording modes such as
recording the peak-to-peak voltage, peak cathodic voltage,
peak anodic voltage, or the entire waveform at each location.
In addition, it offers a variety of filters and graphical displays
for the output waveform. In the experiment conducted in this
paper, the probe scanned horizontally along a cross-section of
the electrodes at a height of 100 µm. It recorded data every
5µm-10µm, depending on the scan.
B.Electrode Array
A 4x4 electrode array composed of 200 µm diameter
platinum electrodes with a pitch of 500 µm is used in the
experiment. Constant current stimulus provided by our custom
retinal application specific integrated circuit (ASIC) stimulator
with independent channel stimulation is adopted to produce
biphasic stimulus with precise amplitude control and temporal
offsets among channels [12]. The electrodes were placed in
the center of a cylindrical tank with a diameter of 29 mm and a
height of 45 mm (see Fig. 1). A ground electrode was placed
along the edge of the tank. The electrodes were immersed in
0.9% w/v saline solution.
Fig. 2 GUI interface for LabView program. [A] Raw output
waveform, [B] Filtered waveform for single pulse, [C] Scan settings,
[D] Cumulative 3D graph displaying recorded values for each
scanned position
Fig. 3 Combined applied stimulus for adjacent electrodes. The dashed
and solid lines represent the individual applied currents to each
respective electrode. Both electrodes have the same stimulation
parameters except the solid line has a 1 ms time delay. When
combined they form a waveform with a 2 ms pulse width
World Academy of Science, Engineering and Technology
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544International Scholarly and Scientific Research & Innovation 8(9) 2014
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3. Fig. 4 Recorded voltage waveforms as probe moves along electrodes. [A], [B], and [C] are the waveforms with voltage on the y axis and time
in ms on the x axis, with their locations corresponding to the probe positions in [D]. [A] is positioned above the left electrode, [B] is positioned
above the center point, and [C] is positioned above the right electrode
C.Stimulation Parameters
We accomplished our virtual electrode stimulating
parameters through stimulating one electrode with a 10 µA
biphasic current, cathode first, with 1 ms pulse width and a
1.75 ms interphase delay. The other electrode was stimulated
with the same parameters except with a 1 ms start delay. 10
µA was chosen because it is still within the range of threshold
currents, yet it is smaller than that used for the traditional
virtual electrode approach [9], [13]. Large currents create heat
that can damage the eye, so we desired to see if our virtual
electrode could be created using small currents that are safer
for both the eye and the electrodes. Reiterating the theory
behind our virtual electrode, it has been shown in [11] that a
short pulse width of 40 µs is unable to activate a neuron,
whereas an 80 µs pulse width will. A stimulus pulse width of
40 µs would thus be desired for actual stimulation of neurons.
As a proof-of-concept, in this experiment, we use a 1 ms
stimulus pulse width that allows us to obtain reliable
measurements from the DAQ card directly and to validate the
virtual electrode theory. We envision that the pulse width can
be further scaled down while the virtual electrode can still be
created since saline or vitreous humor is simply passive
conductive medium.
Fig. 3 shows the waveform of the two applied stimuli and
how they should theoretically combine to form a single
biphasic pulse with a 2 ms pulse width and a 0.75 ms
interphase delay.
III. RESULTS
In order to quantitatively determine whether a virtual
electrode with a pulse width of 2 ms appeared between the two
electrodes, we used our recording device to scan along a linear
cross-section of the two electrodes. Both electrodes were
stimulated with the previously described stimulation
parameters. The electrode designated as ‘left’ has the
stimulation with no start delay and the electrode designated as
‘right’ has the 1 ms start delay. First, a scan was done to
record the potential waveform at each point along the
electrodes. From this scan we can see how the two waveforms
interact (Fig. 4). Above each electrode its own respective
signal dominates: above the left electrode the cathodic voltage
peaks from 0.5 – 1.5 ms and above the right electrode the
cathodic voltage peaks from 1.5 – 2.5 ms. However, in the
center they both contribute equally, forming a steady peak
from 0.5 – 2.5 ms.
A second scan was done which recorded the peak cathodic
voltage at each point along the electrode array (Fig. 5). This
helps us to understand how the magnitude of the potential
changes with position. From Fig. 5 we can also easily
determine the locations for both of the stimulating electrodes
based off of the negative peaks: by defining the middle point
between the two peaks as 0.0 mm, both electrodes are located
approximately 250 µm on either side of the center. This is
supported by the fact that it is known that the electrodes in the
array are separated by 500 µm from center-to-center. The left
electrode has a slightly lower (less negative) peak than the
right electrode, but this is most likely due to slight surface
differences between the two electrodes and should have a
minimal effect on the results and the virtual electrode effect.
A third scan was done along the same cross-section which
recorded the pulse width at each point (Fig. 6). The pulse
width was recorded through the pre-existing Pulse
Measurements signal analysis function within LabView. From
Fig. 6 it can be seen that the pulse width is approximately 1
ms everywhere except -0.1 mm – 0.1 mm, where it peaks at
approximately 1.95 ms. The location of this peak is the virtual
electrode position. It has a pulse width of approximately 2 ms,
which is twice the pulse width of the stimulating electrodes,
exactly what was desired. It is roughly 200 µm wide, which is
Left
Electrode
Right
Electrode
A CB
D
Center
World Academy of Science, Engineering and Technology
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545International Scholarly and Scientific Research & Innovation 8(9) 2014
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4. the same width as the stimulating electrodes. Further tests will
be conducted in order to determine if this size remains
constant or if it varies with different electrode sizes and
pitches. Finally, from Fig. 5 it can be determined that the
cathodic voltage at the virtual electrode is -0.42 V. This is
0.15 V and 0.24 V lower (less negative) than the left and right
electrodes respectively.
Fig. 5 Potential along cross-section of two stimulating electrodes,
recorded during the cathodic spike. The two stimulating electrodes
are located approximately ±0.25 mm from the center point, located at
0.0 mm. Data is recorded every 10 µm
Fig. 6 Pulse width recorded along electrodes. The two stimulating
electrodes are located in the exact same position as in Fig. 3, but
instead of recording the potential it instead recorded the pulse width
at each location. The pulse width is roughly 1 ms at the location of
the two stimulating electrodes, but rises to just short of the desired 2
ms at the middle point between the two. Data is recorded every 5 µm
Reiterating the setup, in this experiment a 1 ms pulse width
was used instead of 40 µs in order to obtain reliable pulse
width measurements. We thus make the assumption for our
proof of concept that the 1 ms pulse will act as the 40 µs and
not activate a neuron, whereas a 2 ms pulse will act as the 80
µs and activate a neuron. This assumes that the behavior of the
virtual electrode obtained for the longer pulses can be applied
to shorter pulse widths.
In order to obtain a clearer view of how this virtual
electrode would appear to a neuron, the range of pulse widths
[1 ms, 2 ms] in Fig. 6 were normalized to [0, 1]. We assume
pulse widths of 2 ms can activate the neurons while those of 1
ms are incapable. The normalized pulse widths are then
multiplied by the cathodic voltages in Fig. 5. This makes the
potential with pulse widths that could activate a neuron
(multiplied by 1) remain and the potential with pulse widths
that could not activate a neuron (multiplied by ~0) canceled.
As a result, Fig. 7 displays only the cathodic voltages from
Fig. 5 that have the correct wavelength to theoretically
activate a neuron.
Fig. 7 Weighted voltage that could activate a neuron. This displays
the cathodic voltage from Fig. 4 that is of the proper pulse width to
theoretically stimulate a neuron
To further determine the virtual electrode’s capability to
stimulate the neuron, the activating function was taken into
account. An activating function dictates whether a neuron will
be activated, and this function is dependent on the second
spatial derivative of the externally applied voltage resulting
from a given current stimulus [14], [15]. We fist calculate and
then compare the 2nd
spatial derivative of the potentials
recorded from a physical electrode and the virtual electrode.
In order to compare the virtual electrode to a single physical
electrode, the right electrode was stimulated on its own and
the potential recorded. Fig. 8 shows the cathodic voltage and
its second derivative found for just the right electrode (Fig. 4
C) with a 10 µA biphasic current with a 2 ms pulse width and
a 0.75 ms interphase delay. This is theoretically the same
parameters as the virtual electrode. The results for the physical
electrode were obtained by only stimulating the right electrode
World Academy of Science, Engineering and Technology
International Journal of Medical, Health, Pharmaceutical and Biomedical Engineering Vol:8 No:9, 2014
546International Scholarly and Scientific Research & Innovation 8(9) 2014
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5. and scanning along a cross-section of it while recording the
peak cathodic voltage at each point, seen in Fig. 8 A. The
resulting potential was then curve-fitted with a 100th
degree
polynomial in order to make the subsequent derivatives
smooth. The 2nd
derivative of it was then calculated (Fig. 8 B).
In Fig. 8 B there is a clear peak at 0.2 mm, which is
approximately where the right electrode has previously been
shown to be. The peak has a value of 17 V/m2
.
Fig. 8 [A] Cathodic voltage of right electrode stimulated with a 10
µA, 2 ms biphasic current. [B] Second spatial derivative of [A]
The same technique was then used upon the weighted
voltage for the virtual electrode from Fig. 7, once again first
curve-fitting the data to a 100th
degree polynomial so that the
derivatives are smooth, and then taking the 2nd
derivative of it
(Fig. 9). In Fig. 9 the peak is centered at 0.0 mm, which is
where the virtual electrode was, and has a peak value of 93.7
V/m2
.
We now compare the potential and 2nd
derivatives of the
physical and virtual electrodes. From Figs. 7-9, even though
the cathodic voltage was lower (less negative) for the virtual
electrode in Fig. 7 than the physical electrode in Fig. 8 A, the
second derivative of the potential is significantly larger for the
virtual electrode in Fig. 9 than for the physical electrode in
Fig. 8 B. This is because the virtual electrode accelerates
much more steeply than the right electrode, which is what the
second derivative is based upon. This is very interesting,
because it suggests that the virtual electrode may be even
more effective than a physical electrode at activating neurons.
Fig. 9 Second spatial derivative of the weighted cathodic voltage
from Fig. 7 The data from Fig. 7 was first curve-fitted to a 100th
degree polynomial and then 2nd derivatives were taken of it
IV. DISCUSSION AND CONCLUSION
A.Summary of Findings
The purpose of this paper was to determine whether a
virtual electrode of twice the pulse width of two stimulating
electrodes could be created that would only activate neurons
above the virtual electrode. We have been able to successfully
demonstrate that through stimulating two adjacent electrodes
with slightly time-offset signals, a waveform with twice the
pulse width will appear directly between the two electrodes.
Additionally, the physical width over which the virtual
electrode spans seems to be comparable to the width of the
stimulating electrodes, although this should be further tested
with electrodes of varying sizes and spacing. In addition, we
were able to weight the virtual electrode’s voltage based upon
pulse width and what could theoretically stimulate a neuron.
From this we have shown that the potential above the virtual
electrode is less than that above the stimulating electrodes.
However, when the activating function is taken into account
the second spatial derivative of the potential above the virtual
electrode is significantly larger than that of the physical
electrodes. This suggests that not only could the virtual
electrode be effective in stimulating neurons, but that it may
be significantly more effective than physical electrodes.
B. Suggestions for Further Research
Although these results are very promising towards the
worth of a virtual electrode, there is still further research to be
done. First, in this experiment, a large pulse width of 1 ms was
World Academy of Science, Engineering and Technology
International Journal of Medical, Health, Pharmaceutical and Biomedical Engineering Vol:8 No:9, 2014
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6. used instead of a 40 µs pulse width in order to obtain reliable
pulse width measurements. We assume that the results
obtained from longer pulses can be applied to shorter pulses,
but further research should be done to determine if similar
results can be found for a pulse width of 40 μs.
Second, this study used pulses of 10 µA, which is on the
smaller end of useful stimulation current amplitudes. Further
research should be concerned with determining whether
similar results can be obtained for larger applied currents.
Third, a limitation of this study is the assumption that
LabView’s measurement of the pulse width accurately
represents how a RGC will also respond to a given pulse
width. The second derivative in Fig. 9 for the virtual electrode
is based on these pulse width measurements, so if RGCs react
differently, the activating function values may change as well.
As such, the next step is to confirm these results by actually
seeing if a virtual electrode composed of two 40 µs pulses
could be used to stimulate real RGCs.
C.Conclusion
This paper presents a stimulation technique that may be
used to maximize the efficacy of electrode arrays by offering
the capability of additional, virtual electrodes. These virtual
electrodes can be created in between any two electrodes, and
are composed of two time-offset biphasic pulses that combine
to form a single biphasic pulse of twice the pulse width in the
center. This technique requires no new technological
modification of current electrode arrays, so it can be
immediately implemented into a retinal prosthetic system by
simply modifying the stimulation parameters. Through this
technique retinal prosthetics can further increase their
resolution without the need to add additional electrodes, which
ultimately will help offer fuller, clearer vision to those who
suffer from retinal degenerative diseases.
ACKNOWLEDGMENT
The author would like to thank Dr. Chih-Wei Chang for his
technical support and discussion.
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World Academy of Science, Engineering and Technology
International Journal of Medical, Health, Pharmaceutical and Biomedical Engineering Vol:8 No:9, 2014
548International Scholarly and Scientific Research & Innovation 8(9) 2014
InternationalScienceIndexVol:8,No:9,2014waset.org/Publication/9999416