VLSI Circuits for Bidirectional Neural Interfaces

Medical devices that deliver electrical stimulation to neural tissue are important clinical tools that can augment or replace pharmacological therapies. The success of such devices has led to an explosion of interest in the field, termed neuromodulation, with a diverse set of disorders being targeted for device-based treatment. Nevertheless, a large degree of uncertainty surrounds how and why these devices are effective. This uncertainty limits the ability to optimize therapy and gives rise to deleterious side effects. An emerging approach to improve neuromodulation efficacy and to better understand its mechanisms is to record bioelectric activity during stimulation. Understanding how stimulation affects electrophysiology can provide insights into disease, and also provides a feedback signal to autonomously tune stimulation parameters to improve efficacy or decrease side-effects. The aims of this work were taken up to advance the state-of-the-art in neuro-interface technology to enable closed-loop neuromodulation therapies. Long term monitoring of neuronal activity in awake and behaving subjects can provide critical insights into brain dynamics that can inform system-level design of closed-loop neuromodulation systems. Thus, first we designed a system that wirelessly telemetered electrocorticography signals from awake-behaving rats. We hypothesized that such a system could be useful for detecting sporadic but clinically relevant electrophysiological events. In an 18-hour, overnight recording, seizure activity was detected in a pre-clinical rodent model of global ischemic brain injury. We subsequently turned to the design of neurostimulation circuits. Three critical features of neurostimulation devices are safety, programmability, and specificity. We conceived and implemented a neurostimulator architecture that utilizes a compact on-chip circuit for charge balancing (safety), digital-to-analog converter calibration (programmability) and current steering (specificity). Charge balancing accuracy was measured at better than 0.3%, the digital-to-analog converters achieved 8-bit resolution, and physiological effects of current steering stimulation were demonstrated in an anesthetized rat. Lastly, to implement a bidirectional neural interface, both the recording and stimulation circuits were fabricated on a single chip. In doing so, we implemented a low noise, ultra-low power recording front end with a high dynamic range. The recording circuits achieved a signal-to-noise ratio of 58 dB and a spurious-free dynamic range of better than 70 dB, while consuming 5.5 μW per channel. We demonstrated bidirectional operation of the chip by recording cardiac modulation induced through vagus nerve stimulation, and demonstrated closed-loop control of cardiac rhythm

Dispositivo de Deteção do Bruxismo do Sono

This thesis aims to explore and, ultimately, develop a system capable of monitoring physiological signals to detect bruxism events. Bruxism is a disorder characterized by the habit of pressing and grinding the teeth. These events can either occur during the day (Awake Bruxism) or during the night (Sleep Bruxism). Studies suggest that 20% of the adult population suffer from Awake Bruxism, and 8-16% from Sleep Bruxism. The consequences of this disorder are several, ranging from tooth wear, dental fractures, or abfraction, resulting in headaches, or facial myalgia. This dissertation focuses on the Sleep Bruxism type since it’s harder to detect and treat. First, a study about the evolution of technology in healthcare is carried out, fundamentally about how it was introduced and how did it get to the point it is now. The topic of wearable devices is also explored, in the sense that it’s where the market is going and how these devices can transform healthcare. Then, the study converges on the devices developed especially for bruxism, namely which devices, and what type of techniques are used. Subsequently, the general concept for the system is elaborated, exploring several options both in terms of devices and physiological data to be parameterized. However, some restrictions exist for the construction of the system. For the construction of an intraoral system, the device has to be of small dimensions and with low energy consumption. With these constraints, the system has implemented an Inertial Measurement Unit to estimate the orientation of the patient’s sleeping position, and force sensors to measure the force exerted between the teeth. For compactness, a Systemon-Chip is used, since it includes an ARM Cortex M4 processor, several peripherals, and an RF transceiver in one package. The system is not only responsible for the data acquisition, but also the data transmission. This is accomplished by using Bluetooth Low Energy, which is one of the most common protocols for low-power devices. Customized service is developed for this purpose, consisting of three different characteristics: the force characteristic, the accelerometer characteristic, and the gyroscope characteristic. The reason is for maximizing efficiency. The last step was to develop the prototype, testing its functionalities and try to project next iterations of the prototype

Ultra low power wearable sleep diagnostic systems

Sleep disorders are studied using sleep study systems called Polysomnography that records several biophysical parameters during sleep. However, these are bulky and are typically located in a medical facility where patient monitoring is costly and quite inefficient. Home-based portable systems solve these problems to an extent but they record only a minimal number of channels due to limited battery life. To surmount this, wearable sleep system are desired which need to be unobtrusive and have long battery life. In this thesis, a novel sleep system architecture is presented that enables the design of an ultra low power sleep diagnostic system. This architecture is capable of extending the recording time to 120 hours in a wearable system which is an order of magnitude improvement over commercial wearable systems that record for about 12 hours. This architecture has in effect reduced the average power consumption of 5-6 mW per channel to less than 500 uW per channel. This has been achieved by eliminating sampled data architecture, reducing the wireless transmission rate and by moving the sleep scoring to the sensors. Further, ultra low power instrumentation amplifiers have been designed to operate in weak inversion region to support this architecture. A 40 dB chopper-stabilised low power instrumentation amplifiers to process EEG were designed and tested to operate from 1.0 V consuming just 3.1 uW for peak mode operation with DC servo loop. A 50 dB non-EEG amplifier continuous-time bandpass amplifier with a consumption of 400 nW was also fabricated and tested. Both the amplifiers achieved a high CMRR and impedance that are critical for wearable systems. Combining these amplifiers with the novel architecture enables the design of an ultra low power sleep recording system. This reduces the size of the battery required and hence enables a truly wearable system.Open Acces

Investigative Development of an UWB Radar for UAS-borne Applications

The engineering ethos of the last decade has been miniaturization. Progress in various industries like material design, semiconductor technology, and digital signal processing has resulted in low-profile electrical systems. This has facilitated the means of integration onto platforms. Sensors such as radars are typically large, heavy, and consume a lot of power. Miniaturization of radars can enable important applications like remote sensing the various aspects of the Earth System from Unmanned Aerial Systems (UAS). Information about natural topography like ice sheets, vegetation cover, and ocean currents can improve our understanding of the natural processes and continued measurements offer insight into the changes over time. Soil plays a vital role in the Earth’s hydrological cycle. The moisture in soil influences the weather, vegetation, and human endeavors like construction. Models are built using an extensive set of temporal soil moisture data to predict natural disasters like droughts, floods, and landslides. It plays a central role in the areas of agriculture and water resource management and hence can influence policy making and economic decisions. In this work, an investigative approach to the design, build, and test of a 2 – 18 GHz Frequency Modulated Continuous Wave radar for snow and soil measurements is reported. The radar system is designed to be integrated to the Vapor 55 rotorcraft, which is a Group 1 UAS. The radar can operate as a scatterometer to measure backscatter signatures in all four combinations of vertical and horizontal polarizations; or as a nadir-looking sounder for fine-resolution snow thickness measurements. One of the primary contributions of this work is the exploration of a single-module that integrates the radar’s RF transmitter, RF receiver, receiver’s IF section, wideband sweep generator, and the DC bias circuitry for the active components. The sweep generator is based on a phase-locked loop and frequency multiplication/translation stage. The compact assembly is in the form of two multilayer Printed Circuit Boards (PCB) merged together and it occupies an area of nearly 170 cm2. This thesis describes the design, construction, and testing of the module, along with recommendations for future revisions. A commercially off-the-shelf module (Arena series by Tomorrow.io, formerly Remote Sensing Solutions) is the digital backend and it consists of an Arbitrary Waveform Generator (AWG) and a data acquisition system capable of sampling up to 250 MSPS. The module is low-profile with dimensions of 7.6 cm x 19.3 cm x 2.3 cm and weighs less than 400 g including the separate aluminum enclosure intended to be integrated with the radar’s RF and mixed-signal sections. A second contribution of this work is the design of a prototype antenna front-end, which consists of four four-element antenna arrays housed in a Delrin plastic fixture and are fed using custom-designed microstrip power dividers. The dimensions of the fixture are 13.7 cm x 5.9 cm x 5.5 cm and the uniform elemental distance is 2.5 cm. The arrays are fastened to a metal sheet and a custom-designed four-layer fiberglass composite fairing protects the arrays. The entire front-end is integrated on the rotorcraft and measured in an anechoic chamber. The measured, fully integrated return loss of each array covers 2 – 18 GHz and the highest value is -7.22 dB at 5.23 GHz. The radiation pattern shows a distinct nadir-pointing main lobe for nearly the entire bandwidth, however the effects of the platform increase the average side-lobe levels to less than 10 dB for 12 – 18 GHz. The measured maximum nadir gain is 15.88 dB at 10 GHz and there is a greater than 6 dB variation in magnitude within the bandwidth. This variation is compensated by processing the backscatter data over distinct sub-bands that have a maximum nadir gain variation of 6 dB. Lastly, the thesis describes two system tests conducted to evaluate the effectiveness of a prototype radar with soil as the target. These are proof-of-concept measurements to detect differences in backscatter signatures between dry and wet soil. Gravimetric measurements of collected soil samples indicate an average change of 9.5% between the two moisture states. The antenna front-end is exclusively characterized using a Vector Network Analyzer and measurements are recorded for both co- and cross-polarization at three look angles of nadir, 15°, and 30°. The relative measurements are repeated on the same patch of land with a 1U version of the miniaturized radar. There are distinct differences in relative received power and backscatter profile for all four polarizations and at each look angle. It is observed that vertical polarization indicates a change in moisture content by an increase in the relative received power over an extended range beyond the primary backscatter signal. The horizontal polarization results in a greater peak received power for the primary backscatter signal, relative to the vertical polarization. The degradation in backscatter profile for vertical polarization is higher than horizontal polarization as a function of angle and this is observed for both dry and wet soil.The ETD Release form has been added to this record as a License bitstrea

Development of Portable Diffuse Optical Spectroscopic Systems For Treatment Monitoring

The goal of this dissertation is to demonstrate the utility of portable, small-scale diffuse optical spectroscopic (DOS) systems for the diagnosis and treatment monitoring of various diseases. These systems employ near-infrared light (wavelength range of 650nm to 950nm) to probe human tissue and are sensitive to changes in scattering and absorption properties of tissues. The absorption is mainly influenced by the components of blood, namely oxy- and deoxy-hemoglobin (HbO2 and Hb) and parameters that can be derived from them (e.g. total hemoglobin concentration [THb] and oxygen saturation, StO2). Therefore, I focused on diseases in which these parameters change, which includes vascular diseases such as Peripheral Atrial Disease (PAD) and Infantile Hemangiomas (IH) as well as musculoskeletal autoimmune diseases such as Rheumatoid Arthritis (RA). In each of these specific diseases, current monitoring techniques are limited by their sensitivity to disease progression or simply do not exist as a quantitative metric. As part of this project, I first designed and built a wireless handheld DOS device (WHDD) that can perform DOS measurements at various tissue depths. This device was used in a 15-patient pilot study for infantile hemangiomas (IH) to differentiate diseased skin from normal skin and monitor the vascular changes during intervention. In another study, I compare the ultra-small form- factor WHDD’s ability to monitor synovitis and disease progression during a patient’s treatment of RA against the capabilities of a proven frequency domain optical tomographic (FDOT) system that has shown to differentiate patients with and without RA. Learning from clinical utility of the WHDD from these two studies, I adapted the WHDD technology to develop a compact multi- channel DOS measurement system to monitor perfusion changes in the lower extremities before and after surgical intervention for patients with peripheral artery disease (PAD). Using this multi- channel system, which we called the vascular optical spectroscopic measurement (VOSM) system, our group conducted a 20-subject pilot study to quantify its ability to monitor blood perfusion before and after revascularization of stenotic arteries in the lower extremities. This proof-of- concept study demonstrated how DOS may help vascular surgeons perform revascularization procedures in the operating room and assists in post-operative treatment monitoring of vascular diseases

The 1992 4th NASA SERC Symposium on VLSI Design

Papers from the fourth annual NASA Symposium on VLSI Design, co-sponsored by the IEEE, are presented. Each year this symposium is organized by the NASA Space Engineering Research Center (SERC) at the University of Idaho and is held in conjunction with a quarterly meeting of the NASA Data System Technology Working Group (DSTWG). One task of the DSTWG is to develop new electronic technologies that will meet next generation electronic data system needs. The symposium provides insights into developments in VLSI and digital systems which can be used to increase data systems performance. The NASA SERC is proud to offer, at its fourth symposium on VLSI design, presentations by an outstanding set of individuals from national laboratories, the electronics industry, and universities. These speakers share insights into next generation advances that will serve as a basis for future VLSI design

Spacelab Science Results Study

Beginning with OSTA-1 in November 1981 and ending with Neurolab in March 1998, a total of 36 Shuttle missions carried various Spacelab components such as the Spacelab module, pallet, instrument pointing system, or mission peculiar experiment support structure. The experiments carried out during these flights included astrophysics, solar physics, plasma physics, atmospheric science, Earth observations, and a wide range of microgravity experiments in life sciences, biotechnology, materials science, and fluid physics which includes combustion and critical point phenomena. In all, some 764 experiments were conducted by investigators from the U.S., Europe, and Japan. The purpose of this Spacelab Science Results Study is to document the contributions made in each of the major research areas by giving a brief synopsis of the more significant experiments and an extensive list of the publications that were produced. We have also endeavored to show how these results impacted the existing body of knowledge, where they have spawned new fields, and if appropriate, where the knowledge they produced has been applied

Air Traffic Management Abbreviation Compendium

As in all fields of work, an unmanageable number of abbreviations are used today in aviation for terms, definitions, commands, standards and technical descriptions. This applies in general to the areas of aeronautical communication, navigation and surveillance, cockpit and air traffic control working positions, passenger and cargo transport, and all other areas of flight planning, organization and guidance. In addition, many abbreviations are used more than once or have different meanings in different languages. In order to obtain an overview of the most common abbreviations used in air traffic management, organizations like EUROCONTROL, FAA, DWD and DLR have published lists of abbreviations in the past, which have also been enclosed in this document. In addition, abbreviations from some larger international projects related to aviation have been included to provide users with a directory as complete as possible. This means that the second edition of the Air Traffic Management Abbreviation Compendium includes now around 16,500 abbreviations and acronyms from the field of aviation