Design and Implementation of a Novel Flash ADC for Ultra Wide Band Applications

This dissertation presents a design and implementation of a novel flash ADC architecture for ultra wide band applications. The advancement in wireless technology takes us in to a world without wires. Most of the wireless communication systems use digital signal processing to transmit as well as receive the information. The real world signals are analog. Due to the processing complexity of the analog signal, it is converted to digital form so that processing becomes easier. The development in the digital signal processor field is rapid due to the advancement in the integrated circuit technology over the last decade. Therefore, analog-to -digital converter acts as an interface in between analog signal and digital signal processing systems. The continuous speed enhancement of the wireless communication systems brings out huge demands in speed and power specifications of high-speed low-resolution analog-to -digital converters. Even though wired technology is a primary mode of communication, the quality and efficiency of the wireless technology allows us to apply to biomedical applications, in home services and even to radar applications. These applications are highly relying on wireless technology to send and receive information at high speed with great accuracy. Ultra Wideband (UWB) technology is the best method to these applications. A UWB signal has a bandwidth of minimum 500MHz or a fractional bandwidth of 25 percentage of its centre frequency. The two different technology standards that are used in UWB are multiband orthogonal frequency division multiplexing ultra wideband technology (MB-OFDM) and carrier free direct sequence ultra wideband technology (DS-UWB). ADC is the core of any UWB receiver. Generally a high speed flash ADC is used in DS-UWB receiver. Two different flash ADC architectures are proposed in this thesis for DS-UWB applications. The first design is a high speed five bit flash ADC architecture with a sampling rate of 5 GS/s. The design is verified using CADENCE tool with CMOS 90 nm technology. The total power dissipation of the ADC is 8.381 mW from power supply of 1.2 V. The die area of the proposed flash ADC is 186 μm × 210 μm (0.039 mm2). The proposed flash ADC is analysed and compared with other papers in the literature having same resolution and it is concluded that it has the highest speed of operation with medium power dissipation. iii The second design is a reconfigurable five bit flash ADC architecture with a sampling rate of 1.25 GS/s. The design is verified using CADENCE tool with UMC 180 nm technology. The total power dissipation of the ADC is 11.71 mW from power supply of 1.8 V. The die area of the implementation is 432 μm × 720 μm (0.31104 mm2). The chip tape out of the proposed reconfigurable flash ADC is made for fabrication

Design of an Ultra-Wideband Frequency-Modulated Continuous Wave Short Range Radar System for Extending Independent Living

Falls in the disabled and elderly people have been a cause of concern as they can be immobilized by the fall and have no way to contact others and seek assistance. The proposed frequency modulated continuous wave (FMCW) short range radar (SRR) system, which uses ultra-wideband (UWB) signals can provide immediate assistance by monitoring and detecting fall events. The unique characteristics of this system allow for a frequency-based modulation system to carry out triangulation and sense the location of the fall through the usage of a continuous chirp signal that linearly sweeps frequency. This project focuses on the development, design and simulation of a ring oscillator that exhibits the frequency modulated signal on a single integrated circuit chip. The ring oscillator is controlled by a voltage ramp signal generator and a voltage to current (V-I) converter. The circuit is designed in Cadence using TSMC 180nm process technology and operates in the frequency range of 3.409 GHz to 5.349 GHz with a spectral bandwidth of 1.94 GHz, which meets the Federal Communications Commission’s standards for unlicensed ultra-wideband transmissions

Energy Harvesting for Self-Powered Wireless Sensors

A wireless sensor system is proposed for a targeted deployment in civil infrastructures (namely bridges) to help mitigate the growing problem of deterioration of civil infrastructures. The sensor motes are self-powered via a novel magnetic shape memory alloy (MSMA) energy harvesting material and a low-frequency, low-power rectifier multiplier (RM). Experimental characterizations of the MSMA device and the RM are presented. A study on practical implementation of a strain gauge sensor and its application in the proposed sensor system are undertaken and a low-power successive approximation register analog-to-digital converter (SAR ADC) is presented. The SAR ADC was fabricated and laboratory characterizations show the proposed low-voltage topology is a viable candidate for deployment in the proposed sensor system. Additionally, a wireless transmitter is proposed to transmit the SAR ADC output using on-off keying (OOK) modulation with an impulse radio ultra-wideband (IR-UWB) transmitter (TX). The RM and SAR ADC were fabricated in ON 0.5 micrometer CMOS process. An alternative transmitter architecture is also presented for use in the 3-10GHz UWB band. Unlike the IR-UWB TX described for the proposed wireless sensor system, the presented transmitter is designed to transfer large amounts of information with little concern for power consumption. This second method of data transmission divides the 3-10GHz spectrum into 528MHz sub-bands and "hops" between these sub-bands during data transmission. The data is sent over these multiple channels for short distances (?3-10m) at data rates over a few hundred million bits per second (Mbps). An UWB TX is presented for implementation in mode-I (3.1-4.6GHz) UWB which utilizes multi-band orthogonal frequency division multiplexing (MB-OFDM) to encode the information. The TX was designed and fabricated using UMC 0.13 micrometer CMOS technology. Measurement results and theoretical system level budgeting are presented for the proposed UWB TX

Realization Limits of Impulse-Radio UWB Indoor Localization Systems

In this work, the realization limits of an impulse-based Ultra-Wideband (UWB) localization system for indoor applications have been thoroughly investigated and verified by measurements. The analysis spans from the position calculation algorithms, through hardware realization and modeling, up to the localization experiments conducted in realistic scenarios. The main focus was put on identification and characterization of limiting factors as well as developing methods to overcome them

Development and Experimental Analysis of Wireless High Accuracy Ultra-Wideband Localization Systems for Indoor Medical Applications

This dissertation addresses several interesting and relevant problems in the field of wireless technologies applied to medical applications and specifically problems related to ultra-wideband high accuracy localization for use in the operating room. This research is cross disciplinary in nature and fundamentally builds upon microwave engineering, software engineering, systems engineering, and biomedical engineering. A good portion of this work has been published in peer reviewed microwave engineering and biomedical engineering conferences and journals. Wireless technologies in medicine are discussed with focus on ultra-wideband positioning in orthopedic surgical navigation. Characterization of the operating room as a medium for ultra-wideband signal transmission helps define system design requirements. A discussion of the first generation positioning system provides a context for understanding the overall system architecture of the second generation ultra-wideband positioning system outlined in this dissertation. A system-level simulation framework provides a method for rapid prototyping of ultra-wideband positioning systems which takes into account all facets of the system (analog, digital, channel, experimental setup). This provides a robust framework for optimizing overall system design in realistic propagation environments. A practical approach is taken to outline the development of the second generation ultra-wideband positioning system which includes an integrated tag design and real-time dynamic tracking of multiple tags. The tag and receiver designs are outlined as well as receiver-side digital signal processing, system-level design support for multi-tag tracking, and potential error sources observed in dynamic experiments including phase center error, clock jitter and drift, and geometric position dilution of precision. An experimental analysis of the multi-tag positioning system provides insight into overall system performance including the main sources of error. A five base station experiment shows the potential of redundant base stations in improving overall dynamic accuracy. Finally, the system performance in low signal-to-noise ratio and non-line-of-sight environments is analyzed by focusing on receiver-side digitally-implemented ranging algorithms including leading-edge detection and peak detection. These technologies are aimed at use in next-generation medical systems with many applications including surgical navigation, wireless telemetry, medical asset tracking, and in vivo wireless sensors

Ultra Wideband

Ultra wideband (UWB) has advanced and merged as a technology, and many more people are aware of the potential for this exciting technology. The current UWB field is changing rapidly with new techniques and ideas where several issues are involved in developing the systems. Among UWB system design, the UWB RF transceiver and UWB antenna are the key components. Recently, a considerable amount of researches has been devoted to the development of the UWB RF transceiver and antenna for its enabling high data transmission rates and low power consumption. Our book attempts to present current and emerging trends in-research and development of UWB systems as well as future expectations

UWB Precise Indoor Localization System Performance, Limitations and its Integration

An indoor localization system that was built at University of Tennessee is extensively studied and improved. The goal of the system is to achieve mm down to sub-mm accuracy/precision. Sub-sampling is used to alleviate the high sampling rate required for UWB signals. Current commercial direct sampling systems are still too slow or prohibitively expensive for UWB applications. We developed two different sub-sampling techniques, but the two systems suffer numerous shortcomings: low throughput, non-robustness, non-linearity. A third system is introduced that achieve both high accuracy and high through-put. Changes in the detection algorithm and the frame synchronization are developed to accommodate the new scheme. We present our efforts to replace hybrid components by recently developed MMIC chips, and an integrated digital module developed by ULM University and UT respectively. Similar localization performance was achieved but rather with significantly reduced power consumption, much smaller footprints, and higher throughput. Step Recovery Diode (SRD) based UWB pulse generators suffer from jitter caused by AM-to-PM conversion, SRD shot noise and clock jitter. A mathematical model for simulation of the jitter and amplitude variation effect in the equivalent time sampling technique has been developed and used in SystemVue simulations. A criterion as an estimate of system accuracy is defined as Signal to Distortion Ratio (SDR) and used. Similarly, a model for AM and PM noise analysis for an SRD based UWB pulse generator is developed that was validated experimentally. We estimate the achievable system localization error. A mathematical model and simulation platform are developed to describe its behavior. Limits on the location accuracy as a function of the parameters of the UWB system are described. A discussion of the dominant reasons for errors that include picoseconds pulsar jitter, sampling clock jitter, sampling rate, and system additive white Gaussian noise (AWGN) is presented. We show a simple method to calculate the total system jitter, and describe error biasing phenomenon as the tag moves approaching one base-station and distancing another. Design curves are provided to determine the specifications of system components to achieve a certain positioning accuracy

Doctor of Philosophy

dissertationSince the late 1950s, scientists have been working toward realizing implantable devices that would directly monitor or even control the human body's internal activities. Sophisticated microsystems are used to improve our understanding of internal biological processes in animals and humans. The diversity of biomedical research dictates that microsystems must be developed and customized specifically for each new application. For advanced long-term experiments, a custom designed system-on-chip (SoC) is usually necessary to meet desired specifications. Custom SoCs, however, are often prohibitively expensive, preventing many new ideas from being explored. In this work, we have identified a set of sensors that are frequently used in biomedical research and developed a single-chip integrated microsystem that offers the most commonly used sensor interfaces, high computational power, and which requires minimum external components to operate. Included peripherals can also drive chemical reactions by setting the appropriate voltages or currents across electrodes. The SoC is highly modular and well suited for prototyping in and ex vivo experimental devices. The system runs from a primary or secondary battery that can be recharged via two inductively coupled coils. The SoC includes a 16-bit microprocessor with 32 kB of on chip SRAM. The digital core consumes 350 μW at 10 MHz and is capable of running at frequencies up to 200 MHz. The integrated microsystem has been fabricated in a 65 nm CMOS technology and the silicon has been fully tested. Integrated peripherals include two sigma-delta analog-to-digital converters, two 10-bit digital-to-analog converters, and a sleep mode timer. The system also includes a wireless ultra-wideband (UWB) transmitter. The fullydigital transmitter implementation occupies 68 x 68 μm2 of silicon area, consumes 0.72 μW static power, and achieves an energy efficiency of 19 pJ/pulse at 200 MHz pulse repetition frequency. An investigation of the suitability of the UWB technology for neural recording systems is also presented. Experimental data capturing the UWB signal transmission through an animal head are presented and a statistical model for large-scale signal fading is developed