Wireless power and data transmission to high-performance implantable medical devices

Novel techniques for high-performance wireless power transmission and data interfacing with implantable medical devices (IMDs) were proposed. Several system- and circuit-level techniques were developed towards the design of a novel wireless data and power transmission link for a multi-channel inductively-powered wireless implantable neural-recording and stimulation system. Such wireless data and power transmission techniques have promising prospects for use in IMDs such as biosensors and neural recording/stimulation devices, neural interfacing experiments in enriched environments, radio-frequency identification (RFID), smartcards, near-field communication (NFC), wireless sensors, and charging mobile devices and electric vehicles. The contributions in wireless power transfer are the development of an RFID-based closed-loop power transmission system, a high-performance 3-coil link with optimal design procedure, circuit-based theoretical foundation for magnetic-resonance-based power transmission using multiple coils, a figure-of-merit for designing high-performance inductive links, a low-power and adaptive power management and data transceiver ASIC to be used as a general-purpose power module for wireless electrophysiology experiments, and a Q-modulated inductive link for automatic load matching. In wireless data transfer, the contributions are the development of a new modulation technique called pulse-delay modulation for low-power and wideband near-field data communication and a pulse-width-modulation impulse-radio ultra-wideband transceiver for low-power and wideband far-field data transmission.Ph.D

A Class-E Inductive Powering Link with Backward Data Communications for Implantable Sensor Systems

The design and implementation of a wireless power and data transfer system based on inductive coupling, having the potential to be used in numerous implantable bio-medical sensors and systems, is presented. The system consists of an external (primary) unit and an internal (secondary) unit. The external unit incorporates a high-efficiency switch-mode Class-E amplifier operating at ~200 kHz for driving the primary coil. The secondary unit consists of a parallel resonant coil followed by the power recovery circuitry. Means for backward data communication from the internal to the external unit over the same pair of coils has been realized using a simple FSK-based modulation scheme incorporated into the internal unit. FSK demodulation and associated filtering are integrated with the base inductive powering system. Prototype system test results indicate the inductive link efficiency can exceed 80% under optimum operating conditions with the overall power transfer efficiency of approximately 30%. The communication system is capable of transmitting up to 10kbps of data with the FSK carrier frequency (i.e., middle-frequency) being only 120kHz. The complete system functions reliably over an inter-coil distances exceeding 2.5cm with a 5V dc supply

Doctor of Philosophy

dissertationMore than a century ago, in his labs in Colorado Springs and New York, Nikola Tesla started experimenting with wireless power transfer (WPT). His ideas were ahead of his time, but they fell into obscurity shortly after his death. Nowadays, WPT is no longer thought of as science fiction: neural prostheses, wearables, cellphones, and even electric vehicles can be powered through WPT. In its most common implementation, WPT leverages the magnetic coupling between resonant transmitter and receiver coils to exchange energy. Considerable work is devoted to the design and optimization of WPT antennas; efficiently transmitting the required amount of power can only be accomplished when the coil coupling is in the right range. In this work, we explore the use of spatial filters in WPT systems. Spatial filters are capable of controlling the harmonic content of an incident wave: subwavelength focal spots, perfect lensing, and diffractionless beams are some of their uses. In the first part of this dissertation, the focus is on the analysis and design of a compact negative permeability metamaterial slab. Compared to other works in the literature, this slab is an extremely small fraction of the wavelength, and works at a low operating frequency. Analysis and experimental validation demonstrate that the resulting metamaterial sample can be used in a 2-coil WPT system to achieve large range and efficiency enhancements. In the second part of this dissertation, the analysis and implementation of holographic screens is presented. A method to reduce the fabrication complexity of the desired holographic screen while maintaining the fidelity of the prescribed field distribution is presented. We demonstrate our method through the analysis, design, and experimental validation of a nondiffractive beam launcher with a Bessel field distribution. Finally, we utilize the analysis and methods presented in this work to design an antenna capable of prescribing a uniform field distribution. Because of this property, this WPT antenna is capable of transmitting near constant power with near constant efficiency to the target receiver load, without the need of an adaptive compensation system