Nowadays it is more clear that the Internet of things (IoT) is not a transient trend but a completely new industry. The internet of things has the capability to enhance current industries (Industry 4.0), as well as to help protecting the environment and people. The latter is the case with the system developed and described in this thesis. The possibilities that IoT brings are due to the interconnection of heterogeneous embedded devices to the internet. This thesis focus on LPWANs (Low Power Wide Area Networks), which is a new set of technologies specifically design for the needs of IoT devices.Due to the recent deploy of NB-IoT (Narrow Band IoT) networks it has become more difficult to know what LPWAN is best for a certain application. Thus, the first half of this thesis involves the comparative study of NB-IoT and LoRaWAN LPWANs. This comparison required an in depth study of each technology, specially on the physical and datalink layers. The comparison briefly displays the main characteristics of each technology and explain the main conclusions in a concise manner. The second part of the thesis describes the development of a GNSS tracker. This tracker will be used on train wagons carrying goods that are dangerous for people and the environment. This thesis report describes the different steps taken, from the requirement specification to the partial development of the software.

In recent years, wind energy technology has become one of the top areas of interest for energy harvesting in the power electronics world. This interest has especially peaked recently due to the increasing demand for a reliable source of renewable energy. In a recent study, the American Wind Energy Association (AWEA) ranked the U.S as the leading competitor in wind energy harvesting followed by Germany and Spain. Although the United States is the leading competitor in this area, no one has been able successfully develop an efficient, low-cost AC/DC convertor for low power turbines to be used by the average American consumer. There has been very little research in low power AC/DC converters for low to medium power wind energy turbines for battery charging applications. Due to the low power coefficient of wind turbines, power converters are required to transfer the maximum available power at the highest efficiency. Power factor correction (PFC) and maximum power point tracking (MPPT) algorithms have been proposed for high power wind turbines. These turbines are out of the price range of what a common household can afford. They also occupy a large amount of space, which is not practical for use in one's home. A low cost AC/DC converter with efficient power transfer is needed in order to promote the use of cheaper low power wind turbines. Only MPPT is implemented in most of these low power wind turbine power converters. The concept of power factor correction with MPPT has not been completely adapted just yet. The research conducted involved analyzing the effect of power factor correction and maximum power point tracking algorithm in AC/DC converters for wind turbine applications. Although maximum power to the load is always desired, most converters only take electrical efficiency into consideration. However, not only the electrical efficiency must be considered, but the mechanical energy as well. If the converter is designed to look like a purely resistive load and not a switched load, a wind turbine is able to supply the maximum power with lower conduction loss at the input side due to high current spikes. Two power converters, VIENNA with buck converter and a Buck-boost converter, were designed and experimentally analyzed. A unique approach of controlling the MPPT algorithm through a conductance G for PFC is proposed and applied in the VIENNA topology. On the other hand, the Buck-boost only operates MPPT. With the same wind profile applied for both converters, an increase in power drawn from the input increased when PFC was used even when the power level was low. Both topologies present their own unique advantages. The main advantage for the VIENNA converter is that PFC allowed more power extraction from the turbine, increasing both electrical and mechanical efficiency. The buck-boost converter, on the other hand, presents a very low component count which decreases the overall cost and volume. Therefore, a small, cost-effective converter that maximizes the power transfer from a small power wind turbine to a DC load, can motivate consumers to utilize the power available from the wind.

Today’s world is becoming increasingly automated and interconnected with billions of smart devices coming online, leading to a steep rise in energy consumption from small microelectronics. This coincides with an urgent push to transform global energy production to green energies, causing disruptions and energy shortages, and making the case for efficient energy use ever more pressing. Two major areas where high growth is expected are the fields of wireless communication and radar sensors. Millimeter-wave frequency bands are planned for fifth-generation (5G) and sixth-generation (6G) cellular communication standards, as well as automotive frequency-modulated continuous wave (FMCW) radar systems for driving assistance and automation. Fast silicon-based technologies enable these advances by operating at high maximum frequencies, such as the silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) technologies. However, even the fastest transistors suffer from low and energy expensive gains at millimeter-wave frequencies. Rather than incremental improvements in circuit efficiency using conventional approaches, a disruptive revolution for green microelectronics could be enabled by exploring the low-power benefits of the super-regenerative receiver for some applications. The super-regenerative receiver uses a regenerative oscillator circuit to increase the gain by positive feedback, through coupling energy from the output back into the input. Careful bias and control of the circuit enables a very large gain from a small number of transistors and a very low energy dissipation. Thus, the super-regenerative oscillator could be used to replace amplifier circuits in high data rate wireless communication systems, or as active reflectors to increase the range of FMCW radar systems, greatly reducing the power consumption. The work in this thesis presents fundamental scientific research into the topic of energy-efficient millimeter-wave super-regenerative receivers for use in civilian wireless communication and radar applications. This research work covers the theory, analysis, and simulations, all the way up to the proof of concept, hardware realization, and experimental characterization. Analysis and modeling of regenerative oscillator circuits is presented and used to improve the understanding of the circuit operation, as well as design goals according to the specific application needs. Integrated circuits are investigated and characterized as a proof of concept for a high data rate wireless communication system operating between 140–220 GHz, and an automotive radar system operating at 60 GHz. Amplitude and phase regeneration capabilities for complex modulation are investigated, and principles for spectrum characterization are derived. The circuits are designed and fabricated in a 130 nm SiGe HBT technology, combining bipolar and complementary metal-oxide semiconductor (BiCMOS) transistors. To prove the feasibility of the research concepts, the work achieves a wireless communication link at 16 Gbit/s over 20 cm distance with quadrature amplitude modulation (QAM), which is a world record for the highest data rate ever reported in super-regenerative circuits. This was powered by a super-regenerative oscillator circuit operating at 180 GHz and providing 58 dB of gain. Energy efficiency is also considerably high, drawing 8.8 mW of dc power consumption, which corresponds to a highly efficient 0.6 pJ/bit. Packaging and module integration innovations were implemented for the system experiments, and additional broadband circuits were investigated to generate custom quench waveforms to further enhance the data rate. For radar active reflectors, a regenerative gain of 80 dB is achieved at 60 GHz from a single circuit, which is the best in its frequency range, despite a low dc power consumption of 25 mW.

The rapid development of technology in the health-care sector has led to the discovery of many new illnesses and improved treatments that were not possible earlier. However, many treatments and medicines for a specific disease often come with several side effects. The accuracy in treatments with an optimal result on specified targets is therefore desired with minimum side effects. This requires that the production and the usage processes should be precise. The scope of this study is not about the medicine production phase but rather on managing a medicine schedule. How many times a medicine should be taken in a day is strongly related to its dosage and following a precise timing plays a crucial role in the individual’s health. As a solution, a pill box based on a low power display (Electronic Paper Display, EPD) together with an embedded system has been introduced by the project owner (Victrix AB, Stockholm) .The pill box should have some different functions like alarms, data logging and wireless reporting. Different types of alarms including ringtone, vibration and voice recording/playing are required as well. To be able to trace the already planned timing for taking medicines, system will be able to save and report history of the past 100 days. Since every single idea for solving different parts of the problem should be tested in real system, a Quantitative Research based on experiments be used and the best possible solution be selected and implemented in the project. Studying technical material and also related works besides analyzing generated data after each experiment were a useful tool for the system integration in this work. As the result, a pill box based on an embedded system was designed and integrated successfully. A hardware platform, in form of a prototype system based on an ARM microcontroller and a compatible embedded software have been designed, improved and tested successfully and are available. At the end of this work, the low power E-paper display works properly, alarms can be set and activated, data can be saved and also sent wirelessly. Basically, the result of this project shows how an embedded system can be specialized and programmed to be able to interact with patients and e.g. nurses in order to make a stable and continuous connection between them. Most of determined goals have been achieved and some of them be changed and modified during the work. Also a few additional functions and improvements be suggested as future work.

This study explores the possibility of miniaturizing magnetoplasmadynamic thrusters (MPDTs) to significantly lower power and discharge current levels compared to most conventional MPDTs. A design alternative for MPDTs using a discharge channel with a rectangular cross-section is presented that enables the implementation of strong external magnetic fields to increase the applied-field Lorentz force. The thruster concept uses heaterless calcium aluminate electride (C12A7:e-) hollow cathodes as the electron source. A prototype of the concept intended for the low-amp current range generates thrust in the low millinewton range with a specific impulse ranging between 400 s and 1200 s at power levels below 500 W but shows high thermal power losses to the anode. A further miniaturized version of the concept intended for the sub-amp current range is thermally more sustainable but requires high mass flow rates to achieve a stable discharge, limiting the achievable specific impulse.

Many image processing algorithms exist that can accurately detect humans and other objects such as vehicles and animals. Many of these algorithms require large amounts of processing often requiring hardware acceleration with powerful central processing units (CPUs), graphics processing units (GPUs), field programmable gate arrays (FPGAs), etc. Implementing an algorithm that can detect objects such as humans at longer ranges makes these hardware requirements even more strenuous as the numbers of pixels necessary to detect objects at both close ranges and long ranges is greatly increased. Comparing the performance of different low-power implementations can be used to determine a trade-off between performance and power. An image differencing algorithm is proposed along with selected low-power hardware that is capable of detected humans at ranges of 500 m. Multiple versions of the detection algorithm are implemented on the selected hardware and compared for run-time performance on a low-power system.

Data acquisition through wireless sensor networks (WSNs) has enormous potential for scalable, distributed, real-time observations of monitored environmental parameters. Despite increasing versatility and functionalities, one critical factor that affects the operation of WSNs is limited power. WSN sensor nodes are usually battery powered, and therefore the long-term operation of the WSN greatly depends on battery capacity and the node's power consumption rate. This thesis focuses on WSN node design to reduce power consumption in order to achieve sustainable power supply. For this purpose, this thesis proposes a Moteino-based WSN node and an energy efficient duty cycle that reduces current consumption in standby mode using an enhanced watchdog timer. The nodes perform radio communication at 915 MHz, for short intervals (180ms) every 10 minutes, and consume 6.8 mA at -14dBm. For testing, the WSN node monitored a low-power combined air temperature, relative humidity, and barometric pressure sensor, together with a typical soil moisture sensor that consumes more power. Laboratory tests indicated average current consumption of ~30µA using these short radio transmission intervals. After transmission tests, field deployment of a star-configured network of nine of these nodes and one gateway node provides a long-term platform for testing under rigorous conditions. A webserver running on a Raspberry Pi connected serially to the gateway node provides real-time access to this WSN.

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