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

Micropower Design of an Energy Autonomous RF Tag for UWB Localization Applications

This paper describes the architecture and the micropower design criteria of a battery-less, energy autonomous, individually addressable RF tag for UWB localization applications, with a focus on baseband circuitry. The tag includes a UHF rectifier, power conversion and management circuits, an addressable wake-up radio module, a microcontroller-based control unit, and circuits for UWB localization. The proposed circuit is suitable for UWB localization either by using passive backscattering of received UWB pulses, or by using active UWB pulses generators. Power for operation is scavenged from a modulated UHF carrier also used for addressing purposes. The circuit is implemented on discrete components in a 3.12 cm2 PCB area. The circuit can wake-up from fully discharged states and operates at distances as high as 10.8 m from a 2W-ERP source in the UHF 865–868 MHz RFID band with a +1.8 dBi receiving antenna. The quiescent power consumption of the tag is 3.88 μW, and the average power consumption at an addressing and activation rate of one time per second is 4.7 μW. The effectiveness of UWB localization was tested in a localization system based on time-difference-of-arrival (TDOA) estimations, consisting of multiple UWB readers and UHF transmitters

Smart energy management and conversion

This chapter introduced power management circuits and energy storage unit designs for sub‐1 mW low power energy harvesting technologies, including indoor light energy harvesting, thermoelectric energy harvesting and vibration energy harvesting. The solutions address several of the problems associated with energy harvesting, power management and storage issues including low voltage operation, self‐start, efficiency (conversion efficiency as well as impact of power consumption of the power management circuit itself), energy density and leakage current levels. Additionally, efforts to miniaturize and integrate magnetic parts as well as integrate discrete circuits onto silicon are outlined to offer improvements in cost, size and efficiency. Finally initial results from efforts to improve energy density of storage devices using nanomaterials are introduced

Robustness and durability aspects in the design of power management circuits for IoT applications

With the increasing interest in the heterogeneous world of the “Internet of Things” (IoT), new compelling challenges arise in the field of electronic design, especially concerning the development of innovative power management solutions. Being this diffusion a consolidated reality nowadays, emerging needs like lifetime, durability and robustness are becoming the new watchwords for power management, being a common ground which can dramatically improve service life and confidence in these devices. The possibility to design nodes which do not need external power supply is a crucial point in this scenario. Moreover, the development of autonomous nodes which are substantially maintenance free, and which therefore can be placed in unreachable or harsh environments is another enabling aspect for the exploitation of this technology. In this respect, the study of energy harvesting techniques is increasingly earning interest again. Along with efficiency aspects, degradation aspects are the other main research field with respect to lifetime, durability and robustness of IoT devices, especially related to aging mechanisms which are peculiar in power management and power conversion circuits, like for example battery wear during usage or hot-carrier degradation (HCD) in power MOSFETs. In this thesis different aspects related to lifetime, durability and robustness in the field of power management circuits are studied, leading to interesting contributions. Innovative designs of DC/DC power converters are studied and developed, especially related to reliability aspects of the use of electrochemical cells as power sources. Moreover, an advanced IoT node is proposed, based on energy harvesting techniques, which features an intelligent dynamically adaptive power management circuit. As a further contribution, a novel algorithm is proposed, which is able to effectively estimate the efficiency of a DC/DC converter for photovoltaic applications at runtime. Finally, an innovative DC/DC power converter with embedded monitoring of hot-carrier degradation in power MOSFETs is designed

RF CMOS Oscillators for Modern Wireless Applications

While mobile phones enjoy the largest production volume ever of any consumer electronics products, the demands they place on radio-frequency (RF) transceivers are particularly aggressive, especially on integration with digital processors, low area, low power consumption, while being robust against process-voltage-temperature variations. Since mobile terminals inherently operate on batteries, their power budget is severely constrained. To keep up with the ever increasing data-rate, an ever-decreasing power per bit is required to maintain the battery lifetime. The RF oscillator is the second most power-hungry block of a wireless radio (after power amplifiers). Consequently, any power reduction in an RF oscillator will greatly benefit the overall power efficiency of the cellular transceiver. Moreover, the RF oscillators' purity limits the transceiver performance. The oscillator's phase noise results in power leakage into adjacent channels in a transmit mode and reciprocal mixing in a receive mode. On the other hand, the multi-standard and multi-band transceivers that are now trending demand wide tuning range oscillators. However, broadening the oscillator’s tuning range is usually at the expense of die area (cost) or phase noise. The main goal of this book is to bring forth the exciting and innovative RF oscillator structures that demonstrate better phase noise performance, lower cost, and higher power efficiency than currently achievable. Technical topics discussed in RF CMOS Oscillators for Modern Wireless Applications include: Design and analysis of low phase-noise class-F oscillators Analyze a technique to reduce 1/f noise up-conversion in the oscillators Design and analysis of low power/low voltage oscillators Wide tuning range oscillators Reliability study of RF oscillators in nanoscale CMO