The Design, Simulation and Implementation of Inductively Powered Sensor Systems: New Applications, Design Methodologies and a Unique Coil Topology

Three case studies have been presented for new applications of inductive energy and data transfer (iEDT)-sensor systems. The first application is a condensation detection system for the windshield of an automobile. The developed iEDT-sensor prototype provides a low cost alternative for wireless dew point measurements which involves no wired connections and so can be easily replaced when the windshield is damaged. The second application involves an iEDT-sensor prototype developed wirelessly query the flow rate in a pipe. For the third application, measurement results were performed for a wireless implant system. The application involves a Wireless Sensor (WS), implanted under the dura mater, which was to be used for long term cortical measurement and stimulation with a very high resolution. A suite of tools provided two independent methods of simulating the coil self resonance, quality factor, coupling and self inductance as well as the overall system efficiency. The inductance and coupling were verified within 10% error compared to measurement results and the resonance, quality factor and efficiency to within 30% error. An accurate simulation of the efficiency was predicated by an accurate simulation of the quality factor at the operating frequency. A series of scripts were also developed to automate the construction of the coil geometry, the simulation control and the compilation of the simulation results. These scripts offered the ability to quickly analyze variations in implementation and their affect on the system parameters and efficiency. For the third application, a new and unique topology for the iEDT-sensor system was presented which resulted in three redundant and independent implant coils each capable of simultaneously delivering power to the sensor electronics. This phased array topology has never before been examined for iEDT-systems as far as is known by the author. The new topology demonstrated a similar efficiency when compared to a single implant coil system of the same dimensions and a similar quality factor. Upon implantation, simulations demonstrated that the expected loss in efficiency should be limited to 10%. SAR-value simulations showed that the ISM frequencies at or below 13.56MHz would be in compliance with FCC regulations. The coupling and self inductance measurements for the phased array coil system were confirmed within 10% error compared to the simulations and the quality factor, self-resonance and efficiency were also shown to be accurate to within 20%. The simulated maximum efficiency of the phased array system was, however, substantially lower than the analytically calculated efficiency due to parasitic effects. The outlook for the work is as follows. The scripts should be expanded to include inductors with magnetic cores in order to allow for high power and low frequency applications as well as 3-D simulations in order to allow for more complex geometries. It should also be possible to increase the efficiency per unit area of the phased array coil system by minimizing the parasitic impedance thereby leading to an efficiency per unit area that is greater than that of a single coil system. The result would be a higher efficiency system, especially important for high power applications. This type of phased array coil approach could also be employed in the coil system of the Wireless Power Supply in order to create large areas which could efficiently supply mobile wireless devices with power

A Novel Power-Efficient Wireless Multi-channel Recording System for the Telemonitoring of Electroencephalography (EEG)

This research introduces the development of a novel EEG recording system that is modular, batteryless, and wireless (untethered) with the supporting theoretical foundation in wireless communications and related design elements and circuitry. Its modular construct overcomes the EEG scaling problem and makes it easier for reconfiguring the hardware design in terms of the number and placement of electrodes and type of standard EEG system contemplated for use. In this development, portability, lightweight, and applicability to other clinical applications that rely on EEG data are sought. Due to printer tolerance, the 3D printed cap consists of 61 electrode placements. This recording capacity can however extend from 21 (as in the international 10-20 systems) up to 61 EEG channels at sample rates ranging from 250 to 1000 Hz and the transfer of the raw EEG signal using a standard allocated frequency as a data carrier. The main objectives of this dissertation are to (1) eliminate the need for heavy mounted batteries, (2) overcome the requirement for bulky power systems, and (3) avoid the use of data cables to untether the EEG system from the subject for a more practical and less restrictive setting. Unpredictability and temporal variations of the EEG input make developing a battery-free and cable-free EEG reading device challenging. Professional high-quality and high-resolution analog front ends are required to capture non-stationary EEG signals at microvolt levels. The primary components of the proposed setup are the wireless power transmission unit, which consists of a power amplifier, highly efficient resonant-inductive link, rectification, regulation, and power management units, as well as the analog front end, which consists of an analog to digital converter, pre-amplification unit, filtering unit, host microprocessor, and the wireless communication unit. These must all be compatible with the rest of the system and must use the least amount of power possible while minimizing the presence of noise and the attenuation of the recorded signal A highly efficient resonant-inductive coupling link is developed to decrease power transmission dissipation. Magnetized materials were utilized to steer electromagnetic flux and decrease route and medium loss while transmitting the required energy with low dissipation. Signal pre-amplification is handled by the front-end active electrodes. Standard bio-amplifier design approaches are combined to accomplish this purpose, and a thorough investigation of the optimum ADC, microcontroller, and transceiver units has been carried out. We can minimize overall system weight and power consumption by employing battery-less and cable-free EEG readout system designs, consequently giving patients more comfort and freedom of movement. Similarly, the solutions are designed to match the performance of medical-grade equipment. The captured electrical impulses using the proposed setup can be stored for various uses, including classification, prediction, 3D source localization, and for monitoring and diagnosing different brain disorders. All the proposed designs and supporting mathematical derivations were validated through empirical and software-simulated experiments. Many of the proposed designs, including the 3D head cap, the wireless power transmission unit, and the pre-amplification unit, are already fabricated, and the schematic circuits and simulation results were based on Spice, Altium, and high-frequency structure simulator (HFSS) software. The fully integrated head cap to be fabricated would require embedding the active electrodes into the 3D headset and applying current technological advances to miniaturize some of the design elements developed in this dissertation

Optimum switch sizing for class DE amplifier

Recently, integrated class DE ampli fiers without matching networks have been proposed as a compact solution to drive a multi-element piezoelectric ultrasound transducer array for high-intensity focused ultrasound (HIFU) therapy. These transducers produce acoustic energy that translates into heat for tissue ablation. In order to steer the focal zone, each element in the transducer array is driven at a different phase. Hence, there's a need for the power amplifi er with a digital control unit in this application. Since each element in the transducer array has a different electrical characteristic and they have to be driven at the same frequency, it is a challenge to drive all transducers in the array at their optimum conditions. This work introduces strategies to determine efficient driving parameters for an entire transducer array. In addition. a method to improve the power efficiency of the class DE amplifi er by choosing the optimum size for switching MOSFETs is also proposed. During the operation of a class DE ampli fier, losses are caused by the ON resistance and the drivers of the MOSFET gate capacitances. These parameters are directly dependent on the size of the switching MOSFETs. A wider MOSFET will have a higher gate capacitance, but lower ON resistance. With the correct sizing, these losses can be greatly reduced to improve power efficiency and prevent excessive heating. The challenge with this method is the wide selection of transducers with varying impedance. As the load impedance changes, the MOSFET size also needs to be changed to maintain the maximum power efficiency. Also, the proposed design must deliver at least 1 W output power to the transducer in order to produce enough acoustic pressure. This output requirement will limit the available technology that can be used to design the amplifi er. In addition, this work also proposes a new driving circuit that consumes less power to operate, and also allows a full 0-360 degree phase shift. The design is simulated with Spectre simulator using 0.35 m 50V CMOS process data available from Austria Micro Systems. The proposed design can deliver 1422mW of average power to 6-elements transducer array, and achieve up to 91% power efficiency

An efficient telemetry system for restoring sight

PhD ThesisThe human nervous system can be damaged as a result of disease or trauma, causing conditions such as Parkinson’s disease. Most people try pharmaceuticals as a primary method of treatment. However, drugs cannot restore some cases, such as visual disorder. Alternatively, this impairment can be treated with electronic neural prostheses. A retinal prosthesis is an example of that for restoring sight, but it is not efficient and only people with retinal pigmentosa benefit from it. In such treatments, stimulation of the nervous system can be achieved by electrical or optical means. In the latter case, the nerves need to be rendered light sensitive via genetic means (optogenetics). High radiance photonic devices are then required to deliver light to the target tissue. Such optical approaches hold the potential to be more effective while causing less harm to the brain tissue. As these devices are implanted in tissue, wireless means need to be used to communicate with them. For this, IEEE 802.15.6 or Bluetooth protocols at 2.4GHz are potentially compatible with most advanced electronic devices, and are also safe and secure. Also, wireless power delivery can operate the implanted device. In this thesis, a fully wireless and efficient visual cortical stimulator was designed to restore the sight of the blind. This system is likely to address 40% of the causes of blindness. In general, the system can be divided into two parts, hardware and software. Hardware parts include a wireless power transfer design, the communication device, power management, a processor and the control unit, and the 3D design for assembly. The software part contains the image simplification, image compression, data encoding, pulse modulation, and the control system. Real-time video streaming is processed and sent over Bluetooth, and data are received by the LPC4330 six layer implanted board. After retrieving the compressed data, the processed data are again sent to the implanted electrode/optrode to stimulate the brain’s nerve cells

Novel MRI Technologies for Structural and Functional Imaging of Tissues with Ultra-short T₂ Values

Conventional MRI has several limitations such as long scan durations, motion artifacts, very loud acoustic noise, signal loss due to short relaxation times, and RF induced heating of electrically conducting objects. The goals of this work are to evaluate and improve the state-of-the-art methods for MRI of tissue with short T₂, to prove the feasibility of in vivo Concurrent Excitation and Acquisition, and to introduce simultaneous electroglottography measurement during functional lung MRI

Development of electronics for microultrasound capsule endoscopy

Development of intracorporeal devices has surged in the last decade due to advancements in the semiconductor industry, energy storage and low-power sensing systems. This work aims to present a thorough systematic overview and exploration of the microultrasound (µUS) capsule endoscopy (CE) field as the development of electronic components will be key to a successful applicable µUSCE device. The research focused on investigating and designing high-voltage (HV, < 36 V) generating and driving circuits as well as a low-noise amplifier (LNA) for battery-powered and volume-limited systems. In implantable applications, HV generation with maximum efficiency is required to improve the operational lifetime whilst reducing the cost of the device. A fully integrated hybrid (H) charge pump (CP) comprising a serial-parallel (SP) stage was designed and manufactured for > 20 V and 0 - 100 µA output capabilities. The results were compared to a Dickson (DKCP) occupying the same chip area; further improvements in the SPCP topology were explored and a new switching scheme for SPCPs was introduced. A second regulated CP version was excogitated and manufactured to use with an integrated µUS pulse generator. The CP was manufactured and tested at different output currents and capacitive loads; its operation with an US pulser was evaluated and a novel self-oscillating CP mechanism to eliminate the need of an auxiliary clock generator with a minimum area overhead was devised. A single-output universal US pulser was designed, manufactured and tested with 1.5 MHz, 3 MHz, and 28 MHz arrays to achieve a means of fully-integrated, low-power transducer driving. The circuit was evaluated for power consumption and pulse generation capabilities with different loads. Pulse-echo measurements were carried out and compared with those from a commercial US research system to characterise and understand the quality of the generated pulse. A second pulser version for a 28 MHz array was derived to allow control of individual elements. The work involved its optimisation methodology and design of a novel HV feedback-based level-shifter. A low-noise amplifier (LNA) was designed for a wide bandwidth µUS array with a centre frequency of 28 MHz. The LNA was based on an energy-efficient inverter architecture. The circuit encompassed a full power-down functionality and was investigated for a self-biased operation to achieve lower chip area. The explored concepts enable realisation of low power and high performance LNAs for µUS frequencies

Modular MRI Guided Device Development System: Development, Validation and Applications

Since the first robotic surgical intervention was performed in 1985 using a PUMA industrial manipulator, development in the field of surgical robotics has been relatively fast paced, despite the tremendous costs involved in developing new robotic interventional devices. This is due to the clear advantages to augmented a clinicians skill and dexterity with the precision and reliability of computer controlled motion. A natural extension of robotic surgical intervention is the integration of image guided interventions, which give the promise of reduced trauma, procedure time and inaccuracies. Despite magnetic resonance imaging (MRI) being one of the most effective imaging modalities for visualizing soft tissue structures within the body, MRI guided surgical robotics has been frustrated by the high magnetic field in the MRI image space and the extreme sensitivity to electromagnetic interference. The primary contributions of this dissertation relate to enabling the use of direct, live MR imaging to guide and assist interventional procedures. These are the two focus areas: creation both of an integrated MRI-guided development platform and of a stereotactic neural intervention system. The integrated series of modules of the development platform represent a significant advancement in the practice of creating MRI guided mechatronic devices, as well as an understanding of design requirements for creating actuated devices to operate within a diagnostic MRI. This knowledge was gained through a systematic approach to understanding, isolating, characterizing, and circumventing difficulties associated with developing MRI-guided interventional systems. These contributions have been validated on the levels of the individual modules, the total development system, and several deployed interventional devices. An overview of this work is presented with a summary of contributions and lessons learned along the way

Emerging Power Electronics Technologies for Sustainable Energy Conversion

This Special Issue summarizes, in a single reference, timely emerging topics related to power electronics for sustainable energy conversion. Furthermore, at the same time, it provides the reader with valuable information related to open research opportunity niches