Download files
Abstract
Bioengineering is increasingly becoming a cutting edge field of technology that
combines the state-of-the art in nano technology, microelectronics, wide bandwidth communications, etc. The devices used in bioengineering such as Implantable Medical Devices (IMD)s create a wide variety of new territories for improving quality of life. As these IMDs progressively evolve, boosted by the notable advances in microelectronics and wireless technologies along with the strong demand for precise diagnosis and monitoring of patients, the role of biotelemetry that can wirelessly communicate biological or physiological data from the IMDs is becoming crucially important. In particular, there has been a steady increase in the demand for high data rate transmission in wireless biotelemetry systems with medium to long operation range during the last decade to enable ubiquitous medical services with high precision in diagnosis.
The current state-of-the art in biotelemetric systems fall far short of the requirements, however, in terms of data rate and operation range, potentially leading to a faulty diagnosis and resulting severe consequences. Moreover, the relatively large area and high power consumption (tens order of nJ per bit) of conventional transceiver architectures make them even more unfavorable for biomedical applications. The major challenge of the research presented in this thesis is the design of a bi-directional wireless biotelemetry system, for real-time diagnosis characterised by high data rate, low area, low power dissipation, and with a reasonable operating range to take advantage of the benefits of the wireless connection. To cope with these requirements, in this work, to the best of the author's knowledge Ultra-Wideband (UWB) technology is employed for the first time in biotelemetry applications. The UWB approach has inherent strengths due to the impulse transmission nature of the digital baseband signal. These strengths include substantial reductions in hardware complexity and power dissipation without comprising data rates, making UWB highly suitable candidate for biotelemetry applications. In this research work, the focus is on wireless capsule endoscope applications that can transmit medical images with the highest data rate required in biotelemetry systems. The target data rate is 200Mbps to enable real-time transmission of VGA quality high resolution medical images. The optimum architecture in in-vivo applications is proposed as a Differential Transmit Reference (DTR) UWB transceiver that is derived from thorough system modelling and simulations including digital baseband synchronisation. An all digital tunable Pulse Generator (PG) based transmitter to be located inside the capsule is also proposed and implemented in a 0.18um standard Complementary Metal Oxide Semiconductor (CMOS) process.
This transmitter achieved impressive results; realising a data rate of 200Mbps with the low power consumption of 27pJ per pulse and the small area of 0.0126mm2 making it optimum for target application of a battery powered device operating inside the human body. The viability of the proposed concept of a DTR
UWB receiver with an envelope detection scheme is confirmed by the measurement results from the first version of receiver implemented in a 0.18um CMOS process. The fully integrated DTR UWB receiver is implemented in a 90nm Radio Frequency (RF) CMOS process. It also achieves impressive results of 200Mbps data rate based on the post-layout simulation result. To the best of the author's knowledge, it is the highest ever reported in biotelemetry systems, with the comparably small power consumption of 0.66nJ per bit under the small area of 1.17mm2.
In conclusion, the designed UWB system is optimum for in-vivo biotelemetry applications, where high data rate transmission, low power dissipation, and area
within a reasonable operating range are mandated. These advantages make it the
most suitable for in-vivo wireless endoscope applications, as well as for sophisticated future biomedical applications which will enable a whole new range of value added services.