Reconfigurable RF Energy Harvester with Customized Differential PCB Antenna

In this work, a RF Energy harvester comprised of a differential RF-DC CMOS converter realized in ST130nm CMOS technology and a customized broadband PCB antenna with inductive coupling feeding is presented. Experimental results show that the system can work with different carrier frequencies and thanks to its reconfigurable architecture the proposed converter is able to provide a regulated output voltage of 2 V over a 14 dB of RF input power range. The conversion efficiency of the whole system peaks at 18% under normal outdoor working conditions

Simultaneous wireless information and power transfer in modern communication systems

Energy harvesting for wireless communication networks is a new paradigm that allows terminals to recharge their batteries from external energy sources in the surrounding environment. A promising energy harvesting technology is wireless power transfer where terminals harvest energy from electromagnetic radiation. Thereby, the energy may be harvested opportunistically from ambient electromagnetic sources or from sources that intentionally transmit electromagnetic energy for energy harvesting purposes. A particularly interesting and challenging scenario arises when sources perform simultaneous wireless information and power transfer (SWIPT), as strong signals not only increase power transfer but also interference. This article provides an overview of SWIPT systems with a particular focus on the hardware realization of rectenna circuits and practical techniques that achieve SWIPT in the domains of time, power, antennas, and space. The article also discusses the benefits of a potential integration of SWIPT technologies in modern communication networks in the context of resource allocation and cooperative cognitive radio networks

Energy harvesting from human and machine motion for wireless electronic devices

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Optimisation and frequency tuning concepts for a vibration energy harvester

With current electronic designs becoming more versatile and mobile, applications that were wired and bulky before have now seen a great reduction in size and increase in portability. However, the issue is that the scaling down in size and cost of electronics has far outpaced the scaling up of energy density in batteries. Therefore, a great deal of research has been carried out to search for alternative power sources that can replace or enhance the conventional battery. Energy harvesting (also known as energy scavenging) is the process whereby ambient energy is captured and stored. The ambient energy here refers to energy that is pre-existing in nature, and is self-regenerating and has extended life time from a battery. After reviewing many possible energy scavenging methods, the conversion of ambient vibrations to electricity is chosen as a method for further research. There are plenty of different methods to transform ambient vibration to electricity, but in this research only piezoelectric and electromagnetic conversions are pursued. In order to harvest the most energy with the harvesting device, the harvester’s fundamental mode must be excited. However, this is not always possible due to fluctuations in the frequency of the vibration source. By being able to change the natural frequencies of the device, the harvester could be more effective in capturing ambient energy. In this thesis, the behaviour of the various types of energy sources is studied and the obtained information is later used to generate a vibration signal for subsequent simulation and experiments. A converter based on a piezoelectric bimorph is investigated. The resultant outputs from the design are compared to the model and the analysis is presented. The mechanical strain distributions on the beam’s surface for five different geometric structures are compared and discussed. This is followed by a discussion of the feasibility of improving the strain distribution by changing the beam’s depth (height) along the cantilever beam length. Lastly, a novel frequency tuning method, which involves applying a different effective electrical damping in different quadrants of the oscillating cycle, is proposed. The results of this analysis are presented, along with experimental results that indicate that the behaviour of the system can be changed over a limited range by changing the effective electrical damping during the oscillation cycle

Biotelemetric Monitoring of Brain Neurochemistry in Conscious Rats Using Microsensors and Biosensors

In this study we present the real-time monitoring of three key brain neurochemical species in conscious rats using implantable amperometric electrodes interfaced to a biotelemetric device. The new system, derived from a previous design, was coupled with carbon-based microsensors and a platinum-based biosensor for the detection of ascorbic acid (AA), O2 and glucose in the striatum of untethered, freely-moving rats. The miniaturized device consisted of a single-supply sensor driver, a current-to-voltage converter, a microcontroller and a miniaturized data transmitter. The redox currents were digitized to digital values by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC), and sent to a personal computer by means of a miniaturized AM transmitter. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption and good linear response in the nanoampere current range. The in-vivo results confirmed previously published observations on striatal AA, oxygen and glucose dynamics recorded in tethered rats. This approach, based on simple and inexpensive components, could be used as a rapid and reliable model for studying the effects of different drugs on brain neurochemical systems

Development of a Step Down DC-DC Converter for Power Grid Energy Harvesting

This work contains an analysis of multiple topologies of DC-DC voltage buck con verters. The main goal of this Thesis is to study and design a functioning Step Down converter for capacitive coupling devices used for energy harvesting from the power AC grid. In order to achieve this goal, multiple topologies and circuits of this type of converter are studied and analysed, so that the requirements for the intended application are met. Since the input is obtained from the AC power grid and the output is connected to a supercapacitor, this results in a large input voltage (over 150V) and a low output voltage (between 1V to 3V), therefore the converter requires a step down voltage conversion ratio of around 130. The DC-DC converter should also have a large input impedance (around 50Mohm) to maximize the energy transferred from the power grid. This mode of operation is not common for regular inductance based DC-DC converters, making this a challenging problem. Moreover, since the amount of energy available from the capacitive coupling is very small, it is also necessary to develop a controller circuit that is capable of created a clock with a very low duty cycle while dissipating less than 50uW.Este trabalho visa analisar várias tipologias de conversores de tensão DC-DC deno minados conversores Buck. O principal objectivo desta Tese é estudar e projectar um conversor DC-DC abaixador de tensão para sistemas de acopelamento electromagnético capacitivo utilizada em aplicações de Energy Harvesting a partir da rede AC. De forma a cumprir este objectivo, várias tipologias são estudadas ao longo deste trabalho, de forma a cumprir as especificações exigidas. Uma vez que o sinal de entrada é obtido a partir da rede AC, e que o output está ligado a um supercondensador, isto faz com que a tensão de entrada seja elevado (Acima dos 150V) e a tensão de saída seja baixa (entre 1V e 3V), como tal o conversor precisa de um rácio de abaixamento bastante elevado de cerca de 130 vezes. O conversor DC-DC deve também ter uma impedância de entrada elevada (cerca de 50MOhm) por forma a maximizar a energia transferida da rede de energia. Estas condições de funcionamento não são habituais para conversores DC-DC indutivos, o que torna este um problema muito desafiante. Adicionalmente, uma vez que a energia disponivel devido ao acopelamento capacitivo é muito reduzida, é necessário desenvolver um circuito controlador capaz gerar um sinal de relógio com um duty cycle reduzido enquanto dissipa menos de 50uW de potência