Low-Power and Programmable Analog Circuitry for Wireless Sensors

Embedding networks of secure, wirelessly-connected sensors and actuators will help us to conscientiously manage our local and extended environments. One major challenge for this vision is to create networks of wireless sensor devices that provide maximal knowledge of their environment while using only the energy that is available within that environment. In this work, it is argued that the energy constraints in wireless sensor design are best addressed by incorporating analog signal processors. The low power-consumption of an analog signal processor allows persistent monitoring of multiple sensors while the device\u27s analog-to-digital converter, microcontroller, and transceiver are all in sleep mode. This dissertation describes the development of analog signal processing integrated circuits for wireless sensor networks. Specific technology problems that are addressed include reconfigurable processing architectures for low-power sensing applications, as well as the development of reprogrammable biasing for analog circuits

Low-Power and Programmable Analog Circuitry for Wireless Sensors

Embedding networks of secure, wirelessly-connected sensors and actuators will help us to conscientiously manage our local and extended environments. One major challenge for this vision is to create networks of wireless sensor devices that provide maximal knowledge of their environment while using only the energy that is available within that environment. In this work, it is argued that the energy constraints in wireless sensor design are best addressed by incorporating analog signal processors. The low power-consumption of an analog signal processor allows persistent monitoring of multiple sensors while the device\u27s analog-to-digital converter, microcontroller, and transceiver are all in sleep mode. This dissertation describes the development of analog signal processing integrated circuits for wireless sensor networks. Specific technology problems that are addressed include reconfigurable processing architectures for low-power sensing applications, as well as the development of reprogrammable biasing for analog circuits

POWER DISTRIBUTION ANALYSIS IN COMPLEX SYSTEMS

Electronic systems are continuously growing nowadays in every ambit and application; concepts like mobile systems, domotic, wireless monitoring are becoming very common, and the reason is the continuous reduction of the energy and time needed to collect, process and send information and data to the end user. The energy management complexity of these systems is increasing in parallel both in terms of efficiency and reliability, in order to increase the lifetime of the application and try to make it energy-autonomous, thus also the power management should not be seen only as an efficient energy conversion stage, but as a complex system which can now manage different energy sources, and ensure an uninterrupted power supply to the application. The problems that must be overcome increase as the number of scenarios where the end applications have to be used: this thesis aims to present some complex power distribution systems and provide a detailed analysis of the strategies necessary to make the solution reliable and efficient

Optically Powered Highly Energy-efficient Sensor Networks

In optically powered networks, both, communication signals and power for remotely located sensor nodes, are transmitted over an optical fiber. Key features of optically powered networks are node operation without local power supplies or batteries as well as operation with negligible susceptibility to electro-magnetic interference and to lightning. In this book, different kinds of optically powered devices and networks are investigated, and selected applications are demonstrated

Optically Powered Highly Energy-efficient Sensor Networks

In optically powered networks, both, communication signals and power for remotely located sensor nodes, are transmitted over an optical fiber. Key features of optically powered networks are node operation without local power supplies or batteries as well as operation with negligible susceptibility to electro-magnetic interference and to lightning. In this book, different kinds of optically powered devices and networks are investigated, and selected applications are demonstrated

Analog baseband circuits for sensor systems

This thesis is composed of six publications and an overview of the research topic, which also summarizes the work. The research presented in this thesis focuses on research into analog baseband circuits for sensor systems. The research is divided into three different topics: the integration of analog baseband circuits into a radio receiver for sensor applications; the integration of an ΔΣ modulator A/D converter into a GSM/WCDMA radio receiver for mobile phones, and the integration of algorithmic A/D converters for a capacitive micro-accelerometer interface. All the circuits are implemented using deep sub-micron CMOS technologies. The work summarizes the design of different blocks for sensor systems. The research into integrated analog baseband circuits for a radio receiver focuses on a circuit structures with a very low power dissipation and that can be implemented using only standard CMOS technologies. The research into integrated ΔΣ modulator A/D converter design for a GSM/WCDMA radio receiver for mobile phones focuses on the implications for analog circuit design emerging from using a very deep sub-micron CMOS process. Finally, in the research into algorithmic A/D converters for a capacitive microaccelerometer interface, new ways of achieving a good performance with low power dissipation, while also minimizing the silicon area of the integrated A/D converter are introduced

Low Power Circuit Design in Sustainable Self Powered Systems for IoT Applications

The Internet-of-Things (IoT) network is being vigorously pushed forward from many fronts in diverse research communities. Many problems are still there to be solved, and challenges are found among its many levels of abstraction. In this thesis we give an overview of recent developments in circuit design for ultra-low power transceivers and energy harvesting management units for the IoT. The first part of the dissertation conducts a study of energy harvesting interfaces and optimizing power extraction, followed by power management for energy storage and supply regulation. we give an overview of the recent developments in circuit design for ultra-low power management units, focusing mainly in the architectures and techniques required for energy harvesting from multiple heterogeneous sources. Three projects are presented in this area to reach a solution that provides reliable continuous operation for IoT sensor nodes in the presence of one or more natural energy sources to harvest from. The second part focuses on wireless transmission, To reduce the power consumption and boost the Tx energy efficiency, a novel delay cell exploiting current reuse is used in a ring-oscillator employed as the local oscillator generator scheme. In combination with an edge-combiner power amplifier, the Tx showed a measured energy efficiency of 0.2 nJ=bit and a normalized energy efficiency of 3.1 nJ=bit:mW when operating at output power levels up to -10 dBm and data rates of 3 Mbps

Voltage and capacitance sensing using time comparison

PhD ThesisWith the rapid advancement of electronic and mechanical system miniaturisation, new application types such as portable systems, internet of things (IoT) and wireless sensor networks (WSNs) have become promising areas of growth for industry. In these areas, the limits on battery life have opened opportunities for energy harvesting to become a commonplace choice as the system power source, which brings its own problems. One of these problems is that energy harvesting is in general a much more variable energy source than batteries and mains power supply, because of the unpredictable and intermittent nature of the external energy environment [1]. This implies that both energy harvesters and the loads they support require significantly more control, tuning and management than if the energy was supplied by traditional means. On the other hand, sensing is also an important aspect for such systems as many of these systems are sensors used to monitor physical parameters in the environment. Another reason is that the control, tuning and management of energy harvesting requires the support of energy/power sensing. It is therefore inevitable that sensing methods need to be developed targeting an environment where energy supply is volatile. However, sensing under a variable energy supply faces numerous problems. One such problem is the energy consumption of the sensing itself. In this regard, the capacitive sensor is widely used for sensing a physical parameter, such as pressure, position, and humidity, as it is suitable for low-power applications with limited energy budgets [2–4]. Another problem faced by sensing under energy supply variability is the difficulty of maintaining stable voltage and/or current references. This thesis is motivated by these issues. In this thesis, a new sensing method is developed based on time domain techniques, which will be shown to be 1) suitable for capacitive sensing of environmental physical parameters, 2) suitable for sensing voltage, from which power and energy information can be derived, supporting energy harvesting management uses, and 3) robust to voltage and power volatility, making sensors derived from this method useful for miniaturised and energy autonomous systems. At the centre of this work is a novel reference-free voltage level-crossing sensor, realised through time comparison techniques. By working in the time domain, it avoids the need for voltage or current references. Two more sophisticated sensors are then developed around this level-crossing sensing engine. The first is a voltage monitor which is capable of sensing the crossing of multiple predefined voltage boundaries within a range, targeting energy harvesting system management uses. The second is a capacitance-to-digital converter which senses and converts the value of a target capacitance to digital value. This could be used to support the monitoring of physical vi parameters in the environment including pressure, temperature, moisture, etc. as these might be made to directly affect the values of capacitances. This thesis describes detailed design theory and reasoning, implementation, and validation of the presented sensors. Circuits are implemented in very-large-scale integration and investigated in the Cadence Analog Design Environment. In addition to analogue simulations, experiments were also conducted on a fabricated chip. Data collected from these simulation and physical experiments show that the time-domain method developed in this work has quantitative and qualitative advantages over existing designs

ShakeNet: A portable wireless sensor network for instrumenting large civil structures

We report our findings from a U.S. Geological Survey (USGS) National Earthquake Hazards Reduction Program-funded project to develop and test a wireless, portable, strong-motion network of up to 40 triaxial accelerometers for structural health monitoring. The overall goal of the project was to record ambient vibrations for several days from USGS-instrumented structures. Structural health monitoring has important applications in fields like civil engineering and the study of earthquakes. The emergence of wireless sensor networks provides a promising means to such applications. However, while most wireless sensor networks are still in the experimentation stage, very few take into consideration the realistic earthquake engineering application requirements. To collect comprehensive data for structural health monitoring for civil engineers, high-resolution vibration sensors and sufficient sampling rates should be adopted, which makes it challenging for current wireless sensor network technology in the following ways: processing capabilities, storage limit, and communication bandwidth. The wireless sensor network has to meet expectations set by wired sensor devices prevalent in the structural health monitoring community. For this project, we built and tested an application-realistic, commercially based, portable, wireless sensor network called ShakeNet for instrumentation of large civil structures, especially for buildings, bridges, or dams after earthquakes. Two to three people can deploy ShakeNet sensors within hours after an earthquake to measure the structural response of the building or bridge during aftershocks. ShakeNet involved the development of a new sensing platform (ShakeBox) running a software suite for networking, data collection, and monitoring. Deployments reported here on a tall building and a large dam were real-world tests of ShakeNet operation, and helped to refine both hardware and software