http://hdl.handle.net/10468/581 2017-09-01T09:44:37Z http://hdl.handle.net/10468/3533 Development and deployment of wireless sensor networks O'Flynn, Brendan Since the late 1990's researchers in both academia and industry have been exploring ways to exploit the potential for Wireless Sensor Networks (WSNs) to revolutionise our understanding of, and interaction with, the world around us. WSNs have therefore been a major focus of research over the past 20 years. While WSNs offer a persuasive solution for accurate real-time sensing of the physical world, they are yet to be as ubiquitous as originally predicted when the technology was first envisaged. Technical difficulties exist which have inhibited the anticipated uptake in WSN technologies, the most challenging of these have been identified as system reliability, battery lifetime, maintenance requirements, node size and ease of use. Over the past decade the Wireless Sensor Networks (WSN) group at the Tyndall National institute has been at the forefront of driving the vision of ubiquitously deployed, extended lifetime, low power consumption embedded systems. These systems are required to provide information rich data streams wirelessly in (close to) real-time, be deployed in the world around us, and address the technical challenges associated with ensuring robust and reliable sensor streams and datasets. The work in this thesis is focused on investigating and addressing these challenges through the development of the new technologies and system integration methodologies required to facilitate and implement WSNs and validate these in real deployments. Specifically, this thesis describes the development and deployment of novel WSN systems in the built environment, in environmental monitoring and in fitness and health monitoring systems. The key research challenges identified and discussed are: a) The development of resource-constrained, extremely low power consumption systems incorporating energy-efficient hardware and software algorithms. b) The development of highly reliable extremely long duration deployments which through the use of appropriate energy harvesting solutions facilitate (near) zero maintenance sensor networks. c) The development of low power consumption miniaturised wearable microsystems. This thesis deals with each of these topics through a selection of peer reviewed publications addressing the theme of long-term, ‘zero maintenance’, low power consumption sensor networks. In this thesis the development of proposed systems and solutions to the key technology barriers to be overcome in the scaled deployment of sensor network systems is described which will enable WSNs to “be invisible, last forever, cost nothing and work out of the box”. 2017-01-01T00:00:00Z http://hdl.handle.net/10468/3630 Medical device design within the ISO 13485 framework O'Shea, Conor The design and development of medical devices has become an increasing complex and regulated process. Little if any consideration is given to the regulatory requirements when developing medical devices in universities. This has resulted in an imposing barrier preventing academic innovation reaching clinical adoption. The scope of universities is not to become the legal manufacturer of medical devices. However, should the development of novel devices ever aim to benefit patient care and reach a clinical setting, design controls must be implemented throughout the project life cycle to demonstrate feasibility and safety. The aim of this thesis is to develop user-centred technologies which comply with industrial design control practices whilst helping to bolster and promote innovation within academia. Four projects relating to medical devices have been designed in response to well-defined and end-user-originated clinical needs. These devices can serve as the exemplar for the framework developed in this work with each reaching staggered phases of development within a controlled design process. Although unique, the devices have significant overlapping characteristics that lend the devices to parallel development, leveraging in-house know-how and ‘lessons learned’ into the process of innovation. This thesis focuses on the novelty and design of the aforementioned projects in a discrete structured approach and reflects on the development of each project within the context of a design control process which was developed as part of this work. It is the ultimate goal of this work to develop a flexible structured system compliant with the international requirements for product design and development which may be exported internationally. However, the full execution of this ambition was limited due physical, and financial limitations. This manuscript will describe the technical and commercial opportunity of devices and reflects on the success of developing same within a design control process developed as part of this work. 2017-01-01T00:00:00Z http://hdl.handle.net/10468/4053 Thin film technology for optoelectronics and their thermal management Quan, Zhiheng Thin-film semiconductor optoelectronics are important for applications from optical communication, solid-state lighting, and wearable electronics to biomedical sensors. It is now possible to separate the micrometer-thick device layers from their native substrates and transfer them onto new platforms to optimize system performance and integration. The understanding of thermal management for such devices is very important in order to control the junction temperature effectively. Here, the laser-lift-off (LLO) technique was theoretically and experimentally studied. The temperature distribution at the III-nitride/sapphire interface induced by absorption of 248-nm KrF excimer energetic laser pulses was simulated to verify the experimental results. A 1.5-m-thick n-type Al0.6Ga0.4N membrane was separated from a c-plane sapphire substrate and then bonded to a Si substrate. The electrical behaviour of Ti/Al/Ti/Au contacts on the N-polar n-Al0.6Ga0.4N membrane was characterized. Furthermore, free-standing semipolar InGaN/GaN light-emitting diodes (LEDs) emitting at 445 nm were first realized by separation from patterned r-plane sapphire substrate using LLO. The LEDs showed a turn-on voltage of 3.6 V and output power of 0.87 mW at 20 mA. Electroluminescence measurements showed stronger emission intensity along the inclined c-direction. The -3 dB bandwidth of the LEDs is in excess of 150 MHz at 20 mA and a back-to-back data transmission rate at 300 Mbps is demonstrated. This indicates that the LEDs can be used for high bandwidth visible light communications. For thermal management of thin-film optoelectronics, a GaAs based laser diode (LD) was investigated. The 2-dimensional temperature distribution of the transfer-bonded LD was simulated; where the power dissipation, the thermal resistance of different cavity lengths and configurations were investigated. This can be utilized to optimize the device design and the choice of carrier substrate for efficient thermal management of thin-film optoelectronics. 2017-01-01T00:00:00Z http://hdl.handle.net/10468/4056 High speed IC designs for low power short reach optical links Zhou, Shiyu In this thesis, I have briefly introduced the background of my PhD research, current state-of-the-art design, and my PhD research objectives. Then, I demonstrate how to optimize the performance of PAM-4 transmitters based on lumped Silicon Photonic Mach-Zehnder Modulators (MZMs) for short-reach optical links. Firstly, we analyze the trade-off that occurs between extinction ratio and modulation loss when driving an MZM with a voltage swing less than the MZM’s Vπ. This is important when driver circuits are realized in deep submicron CMOS process nodes. Next, a driving scheme based upon a switched capacitor approach is proposed to maximize the achievable bandwidth of the combined lumped MZM and CMOS driver chip. This scheme allows the use of lumped MZM for high speed optical links with reduced RF driver power consumption compared to the conventional approach of driving MZMs (with transmission line based electrodes) with a power amplifier. This is critical for upcoming short-reach link standards such as 400Gb/s 802.3 Ethernet. The driver chip was fabricated using a 65nm CMOS technology and flip-chipped on top of the Silicon Photonic chip (fabricated using IMEC’s ISIPP25G technology) that contains the MZM. Open eyes with 4dB extinction ratio for a 36Gb/s (18Gbaud) PAM- 4 signal are experimentally demonstrated. The electronic driver chip has a core area of only 0.11mm 2 and consumes 236mW from 1.2V and 2.4V supply voltages. This corresponds to an energy efficiency of 6.55pJ/bit including Gray encoder and retiming, or 5.37pJ/bit for the driver circuit only. In the future, system level analysis should be carried out to investigate the critical pattern issue of the PAM4 optical transmitter. The potential solutions toward 1pJ/bit are given (lumped EAM and micro-ring modulator). In addition, the advanced modulation formats (16 QAM, discrete multitone modulation, and FFE) are presented based on the switched capacitor approach. 2017-01-01T00:00:00Z