1,721,143 research outputs found
A Switched Capacitor based Micro-stimulator for Deep Brain Stimulation
No full textGaurav, Bawa. A Switched Capacitor based micro-stimulator for Deep Brain Stimulation. (under the direction of Dr. Maysam Ghovanloo and Dr. Leda Lunardi)
This thesis presents a novel technique for the development of an implantable stimulator for Deep Brain Stimulation. The key idea is to harvest energy from an inductive link using an efficient switching mechanism at the secondary side. To validate the concept, extensive characterization was performed by simulating explicit differential equations in MATLAB in addition to a prototype implementation in standard CMOS technology. In principle, a zero current switching methodology at the secondary coil has proved to be extremely energy efficient due to no extra wastage of power in the parallel resonant circuits.
A high efficiency full-wave rectifier has been implemented in standard CMOS technology, which ensures a measured efficiency of ~ 85 % while delivering ~ 19 mW of power to the load at 500 KHz input frequency. The underlying principle is that of synchronous rectification, minimization of MOS switch resistance through biasing in deep triode and blockage of reverse currents from the load to source using a lossless capacitive voltage divider technique.
Dual-mode backtelemetry has been incorporated in a full-wave active rectifier with minimal area overhead and an increased data rate and reading range in measurement results, when the rectifier loading varies over time
A Multi-Channel Wireless Implantable Neural Recording System
No full textABSTRACT
YIN, MING. A Multi-Channel Wireless Implantable Neural Recording System. (Under the direction of Dr. Maysam Ghovanloo).
This dissertation presents a multi-channel implantable wireless neural recording (WINeR) system for electrophysiology and behavioral neuroscience research applications. This system consists of two units: a system-on-a-chip (SoC) transmitter unit and a receiver unit built with off-the-shelf components. A novelty of the WINeR system is in its utilization of a wireless single-slope ADC technique by inserting a wireless link in between a pulse width modulator and a time-to-digital converter (TDC). This technique not only offers the WINeR system the benefit of a single-slope ADC, but also makes the WINeR transmitter unit very simple, low power, and small in regards to chip area. In addition, by directly transmitting pulse width modulation (PWM) signal, the pulse rate over the wireless link is reduced to the sampling rate, while a moderate system resolution can still be achieved. Another novelty of this system is that its transmitter uses an asynchronous (clockless) topology and achieves very low noise levels by eliminating the on-chip clock. Some of the other features of this system are the wideband FSK demodulator and FPGA-based TDC in the receiver unit capable of achieving high resolution, low noise, low power, low cost, and ease of implementation.
A 32-channel WINeR transmitter prototype is implemented in a standard CMOS technology, and operates in the 900MHz ISM band. A prototype WINeR receiver is also built using off-the-shelf components with up to 75MHz bandwidth. A custom developed VC++ GUI running on a PC interface with the receiver unit through a USB port and facilitates data storage and visualization. In addition, detailed noise analysis is conducted both theoretically and experimentally to further characterize the performance of the system. Finally, the full functionality of the entire WINeR system has been validated from bench-top, and through in vivo experiments on rats
A Wideband Power Efficient Inductive Link for Implantable Biomedical Devices using Multiple Carrier Frequencies
No full textThis thesis presents a novel inductive link for wireless transmission of power and data to biomedical implantable microelectronic devices using multiple carrier frequencies. Achieving higher data bandwidth without compromising the power efficiency is the driving force to use two separate carriers. Two separate pairs of coils have been utilized for inductive power and forward data transmission. One major challenge, however, is to minimize the interference among these carriers especially on the implantable side, where size and power are highly limited. Planar power coils with spiral shape are optimized in geometry to provide maximum coupling coefficient, k. The data coils are designed rectangular in shape and wound across the power coils diameter to be oriented perpendicular to the power coil planes. The goal is to maximize data coils direct coupling, while minimize their cross-coupling with the power coils. The effects of coils geometry, relative distance, and misalignments on the coupling coefficients have been modeled and experimentally measured.
A prototype system is built to test the functionality of the approach. Frequency Shift Keying (FSK) is used to transmit data using two carriers at 6 and 12 MHz. Power is transmitted at 500 kHz. We achieved power efficiency of 43% at a nominal distance of 10 mm. We also achieved very minimal power interference on to data using the devised coil arrangement. Initial results show the functionality of the design. The inductive link needs more tuning to reduce the Bit Error Rate (BER) for successful operation of an implantable micro stimulating system.
In addition a novel back telemetry link is developed to transmit data back from the implant. This data gives information related to received power, electrode impedances etc, to the external part of the system operation and helps achieve a more stable closed loop system. We have also designed and developed a Manchester encoded FSK Data demodulator circuit to be used in our multi carrier system but have not tested it
WIRELESS POWERING AND TELEMETRY FOR FLEXIBLE BIOELECTRONIC IMPLANTS
No full textPh.DDOCTOR OF PHILOSOPH
Incorporating Back Telemetry in a Full-Wave CMOS Rectifier for RFID and Biomedical Applications
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