Energy Efficient Computing with Time-Based Digital Circuits

University of Minnesota Ph.D. dissertation. May 2019. Major: Electrical Engineering. Advisor: Chris Kim. 1 computer file (PDF); xv, 150 pages.Advancements in semiconductor technology have given the world economical, abundant, and reliable computing resources which have enabled countless breakthroughs in science, medicine, and agriculture which have improved the lives of many. Due to physics, the rate of these advancements is slowing, while the demand for the increasing computing horsepower ever grows. Novel computer architectures that leverage the foundation of conventional systems must become mainstream to continue providing the improved hardware required by engineers, scientists, and governments to innovate. This thesis provides a path forward by introducing multiple time-based computing architectures for a diverse range of applications. Simply put, time-based computing encodes the output of the computation in the time it takes to generate the result. Conventional systems encode this information in voltages across multiple signals; the performance of these systems is tightly coupled to improvements in semiconductor technology. Time-based computing elegantly uses the simplest of components from conventional systems to efficiently compute complex results. Two time-based neuromorphic computing platforms, based on a ring oscillator and a digital delay line, are described. An analog-to-digital converter is designed in the time domain using a beat frequency circuit which is used to record brain activity. A novel path planning architecture, with designs for 2D and 3D routes, is implemented in the time domain. Finally, a machine learning application using time domain inputs enables improved performance of heart rate prediction, biometric identification, and introduces a new method for using machine learning to predict temporal signal sequences. As these innovative architectures are presented, it will become clear the way forward will be increasingly enabled with time-based designs

Exploiting Near Field and Surface Wave Propagation for Implanted Devices

<p>This thesis examines the bandwidth shortcomings of conventional inductive coupling biotelemetry systems for implantable devices, and presents two approaches toward an end-to-end biotelemetry system for reducing the power consumption of implanted devices at increased levels of bandwidth. By leveraging the transition zone between the near and far field, scattering in the near field at UHF frequencies for increased bandwidth at low power budgets can be employed. Additionally, taking advantage of surface wave propagation permits the use of single-wire RF transmission lines in biological tissue, offering more efficient signal routing over near field coupling resulting in controlled implant depth at low power budgets.</p><p>Due to the dielectric properties of biological tissue, and the necessity to operate in the radiating near field to communicate via scattered fields, the implant depth drives the carrier frequency. The information bandwidth supplied by each sensing electrode in conventional implants also drives the operating frequency and regime. At typical implant depths, frequencies in the UHF range permit operation in the radiating near field as well as sufficient bandwidth.</p><p>Backscatter modulation provides a low-power, high-bandwidth alternative to conventional low frequency inductive coupling. A prototype active implantable device presented in this thesis is capable of transmitting data at 30 Mbps over a 915 MHz link while immersed in saline, at a communication efficiency of 16.4 pJ/bit. A prototype passive device presented in this thesis is capable of operating battery-free, fully immersed in saline, while transmitting data at 5 Mbps and consuming 1.23 mW. This prototype accurately demodulates neural data while immersed in saline at a distance of 2 cm. This communication distance is extended at similar power budgets by exploiting surface wave propagation along a single-wire transmission line. Theoretical models of single-wire RF transmission lines embedded in high permittivity and conductivity dielectrics are validated by measurements. A single-wire transmission line of radius 152.4 um exhibits a loss of 1 dB/cm at 915 MHz in saline, and extends the implant depth to 6 cm while staying within SAR limits.</p><p>This work opens the door for implantable biotelemetry systems to handle the vast amount of data generated by modern sensing devices, potentially offering new insight into neurological diseases, and may aid in the development of BMI's.</p>Dissertatio

Telemedicine

Telemedicine is a rapidly evolving field as new technologies are implemented for example for the development of wireless sensors, quality data transmission. Using the Internet applications such as counseling, clinical consultation support and home care monitoring and management are more and more realized, which improves access to high level medical care in underserved areas. The 23 chapters of this book present manifold examples of telemedicine treating both theoretical and practical foundations and application scenarios

Applications of MATLAB in Science and Engineering

The book consists of 24 chapters illustrating a wide range of areas where MATLAB tools are applied. These areas include mathematics, physics, chemistry and chemical engineering, mechanical engineering, biological (molecular biology) and medical sciences, communication and control systems, digital signal, image and video processing, system modeling and simulation. Many interesting problems have been included throughout the book, and its contents will be beneficial for students and professionals in wide areas of interest