Comparative Study on Performance and Variation Tolerance of Low Power Circuit

The demand for low-power electronic devices is increasing rapidly in current VLSI technology. Instead of conventional CMOS circuit operating at nominal supply voltage, several kinds of circuits are brought about with the goal of reducing power consumption. This research is mainly focused on evaluating performance, power and variation tolerance of near/sub-threshold computing and adiabatic logic circuits. Arithmetic logic units (ALUs) are designed with 15nm FinFET process technologies for these circuit styles. The evaluation is carried out by simulations on these ALU designs. The variation model considers ambient temperature variations and power supply fluctuations that emulate wireless sensor node applications. The results shows that conventional static CMOS circuit operating in near-threshold region exhibits similar power efficiency with adiabatic logic circuit operating in the same region, while at the same time it bears better temperature and voltage variation tolerance in most of the cases. The study results provide helpful guidance to low-power electronic system designs

Efficient Archietecture for Effective Utilization of Harvested Power in Microscale Energy Harvesting

Recent developments in combining sensors, microprocessors, and radio frequency (RF) communications holds the potential to revolutionize the way we monitor and maintain critical systems. In the future, literally billions of wireless sensors may become deeply embedded within machines, structures, and the environment. Sensed information will be automatically collected, compressed, and forwarded for condition based maintenance. Energy Harvesting comprises a promising solution to one of the key problems faced by battery-powered Wireless Sensor Networks, namely the limited nature of the energy supply (finite battery capacity). By harvesting energy from the surrounding environment, the sensors can have a continuous lifetime without any needs for battery recharge or replacement

Wireless communication over NFC with a constrained resouce device

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 201

2.45ghz Rf-front End for a Micro Neural Interface System

Active implants inside the human body must be capable of performing their intended function for decades without replacement with minimal tissue heating. It is therefore necessary for them to efficiently operate reliably in a battery free environment at very low power levels. Traditionally inductive coupling has been the preferred choice of power transfer to the active implants. Inductive coupling suffers from bandwidth and alignment issues that limit their usefulness for distributed sensor systems. The ability to use both near-field and far-field RF to power and communicate with sensors distributed in the body would provide a major advance in implantable device technology. Recent advances in wafer packaging technologies and advanced VLSI processes offer the possibility of highly reliable system on chip (SOC) solutions using RF energy as a source to power the active implants. In this paper we present a CMOS VLSI implementation of a front end system for a RFID Sensor (RFIDS) capable of harvesting up to 42�W at -3dBm power levels and providing 700mV and 400mV regulated DC voltages under 50 �A and 4�A continuous load currents respectively. In addition the RFIDS contains both an AM demodulator and a 400mV voltage reference. The RF front end chip occupies an area of 2.32 mm2 and has been fabricated in 180nm IBM CMRF7SF processSchool of Electrical & Computer Engineerin

Vibration energy harvesters for wireless sensor networks for aircraft health monitoring

Traditional power supply for wireless sensor nodes is batteries. However, the application of batteries in WSN has been limited due to their large size, low capacity, limited working life, and replacement cost. With rapid advancements in microelectronics, power consumption of WSN is getting lower and hence the energy harvested from ambient may be sufficient to power the tiny sensor nodes and eliminate batteries completely. As vibration is the widespread ambient source that exists in abundance on an aircraft, a WSN node system used for aircraft health monitoring powered by a piezoelectric energy harvester was designed and manufactured. Furthermore, simulations were performed to validate the design and evaluate the performance. In addition, the Z-Stack protocol was migrated to run on the system and initial experiments were carried out to analyse the current consumption of the system. A new approach for power management was reported, the execution of the operations were determined by the amount of the energy stored on the capacitor. A novel power saving interface was also developed to minimise the power consumption during the voltage measurement

Prototype development for application of a rf energy harvester for 2.4ghz band

Radio Frequency Identification is a wireless communication technology which utilizes radio waves to transmit information. This emerging technology has been available for over 50 years yet has only become customary in recent years. For better understanding, the barcode available on groceries items usually serves the same application principle as the RFID. Active or Passive tags are normally associated when dealing with RFID. The major difference of these tags is the presence of an internal battery source. One of the major setbacks in RFID technology is the limitation of the active tag internal battery. Replacement of these batteries usually consumes time and is a hassle. One of the feasible recommendations is to overcome the battery replacement in the RFID tag by harvesting ambient RF waves from surrounding using a RF energy harvester. In the context of this project, the RF energy harvester that is utilized will be a 7-stage Cockroft-Walton rectifier with band pass filters (BPF) and Bessel low pas filter (LPF) integrated on 1.57mm RT/Duroid 5880 (RO5880) laminated thickness operating in 2.45GHz of the transmission medium equivalent to the transmission of the Wi-Fi signal. Since the output energy obtained from the harvester is figuratively low and un-usable. A step –up circuit with charging and storage function will be implemented to produce a more usable energy output. The main component that will be utilized in the proposed design is a power harvesting integrated circuit (IC), LTC 3105. The simulation for the proposed circuit design is done using Linear Technology (LT) Spice Software followed by fabrication of design on to Printed Circuit Board (PCB) using the EAGLE Software. Upon completion of the prototype, the functionality of the prototype was tested under ideal situation where, an output of 5V and 100mA was achieved with a constant supply of 2.45GHz at (-5dBm) which yields and efficiency of 80%

An Integrated AC-DC Rectifier Converter for Low Voltage Piezoelectric Energy Harvesting and Constant-Voltage Lithium-Ion Cell Charging Application

Energy harvesting is probably one the most sought after solutions that is being given attention to and has become of great importance for last few years. Due to advances in microelectronics and growing demand of autonomous devices, researchers have been working on harvesting energy from ambient sources such as solar, thermal, wind and kinetic energy. Also, growth of rechargeable battery technology has resulted in research in ambient energy harvesting for charging purposes. In this field, piezoelectric effect has been identified as a viable solution to address both low power applications and battery charging applications. Piezoelectric effect is described as the phenomenon of generating a voltage from a mechanical stress and vice-versa. Piezoelectric elements have been seen to offer outstanding performance in scavenging energy because of their high power density, which make them suitable for integrated micro-generators. Many vibration-based harvesting technology use piezoelectric transducers as AC power source. This work emphasizes on vibration based piezoelectric energy harvesting from a very low input voltage source. The main objective of the thesis is to design a power converter that can successfully rectify and boost piezoelectric AC voltages from a few hundred millivolts to a stable usable DC voltage without the use of a bridge diode rectifier circuit. The thesis begins with the introduction to the concept of energy harvesting and piezoelectricity, followed by investigation of a 13x25 mm, 28µm thick, laminated piezoelectric thin film made of Polyvinylidene Fluoride (PVDF) acting as the transducer. The transducer was subjected to a repeated vibration impulse and its resultant voltage response was determined. The thesis then moves towards presenting an integrated AC-DC rectifier converter which eliminates the use of full bridge diode rectifiers that have been known for being inefficient for low power energy harvesting. The stages of operation of the power converter is presented along with the simulation results. The work has also been extended to show the charging application of a Lithium-Ion thin film cell under constant voltage charging scheme using a MATLAB/SIMULINK battery model. A prototype of the converter was also built in the laboratory and presented to show the performance of the integrated AC-DC rectifier converter. A dSPACE controller board was employed to implement the open loop control and the converter switching scheme. Experimental results were presented and assessed before finally moving onto the conclusion and suggested future works

Energy Harvesting for Self-Powered Wireless Sensors

A wireless sensor system is proposed for a targeted deployment in civil infrastructures (namely bridges) to help mitigate the growing problem of deterioration of civil infrastructures. The sensor motes are self-powered via a novel magnetic shape memory alloy (MSMA) energy harvesting material and a low-frequency, low-power rectifier multiplier (RM). Experimental characterizations of the MSMA device and the RM are presented. A study on practical implementation of a strain gauge sensor and its application in the proposed sensor system are undertaken and a low-power successive approximation register analog-to-digital converter (SAR ADC) is presented. The SAR ADC was fabricated and laboratory characterizations show the proposed low-voltage topology is a viable candidate for deployment in the proposed sensor system. Additionally, a wireless transmitter is proposed to transmit the SAR ADC output using on-off keying (OOK) modulation with an impulse radio ultra-wideband (IR-UWB) transmitter (TX). The RM and SAR ADC were fabricated in ON 0.5 micrometer CMOS process. An alternative transmitter architecture is also presented for use in the 3-10GHz UWB band. Unlike the IR-UWB TX described for the proposed wireless sensor system, the presented transmitter is designed to transfer large amounts of information with little concern for power consumption. This second method of data transmission divides the 3-10GHz spectrum into 528MHz sub-bands and "hops" between these sub-bands during data transmission. The data is sent over these multiple channels for short distances (?3-10m) at data rates over a few hundred million bits per second (Mbps). An UWB TX is presented for implementation in mode-I (3.1-4.6GHz) UWB which utilizes multi-band orthogonal frequency division multiplexing (MB-OFDM) to encode the information. The TX was designed and fabricated using UMC 0.13 micrometer CMOS technology. Measurement results and theoretical system level budgeting are presented for the proposed UWB TX

CMOS indoor light energy harvesting system for wireless sensing applications

Dissertação para obtenção do Grau de Doutor em Engenharia Electrotécnica e de ComputadoresThis research thesis presents a micro-power light energy harvesting system for indoor environments. Light energy is collected by amorphous silicon photovoltaic (a-Si:H PV) cells, processed by a switched-capacitor (SC) voltage doubler circuit with maximum power point tracking (MPPT), and finally stored in a large capacitor. The MPPT Fractional Open Circuit Voltage (VOC) technique is implemented by an asynchronous state machine (ASM) that creates and, dynamically, adjusts the clock frequency of the step-up SC circuit, matching the input impedance of the SC circuit to the maximum power point (MPP) condition of the PV cells. The ASM has a separate local power supply to make it robust against load variations. In order to reduce the area occupied by the SC circuit, while maintaining an acceptable efficiency value, the SC circuit uses MOSFET capacitors with a charge reusing scheme for the bottom plate parasitic capacitors. The circuit occupies an area of 0.31 mm2 in a 130 nm CMOS technology. The system was designed in order to work under realistic indoor light intensities. Experimental results show that the proposed system, using PV cells with an area of 14 cm2, is capable of starting-up from a 0 V condition, with an irradiance of only 0.32 W/m2. After starting-up, the system requires an irradiance of only 0.18 W/m2 (18 mW/cm2) to remain in operation. The ASM circuit can operate correctly using a local power supply voltage of 453 mV, dissipating only 0.085 mW. These values are, to the best of the authors’ knowledge, the lowest reported in the literature. The maximum efficiency of the SC converter is 70.3% for an input power of 48 mW, which is comparable with reported values from circuits operating at similar power levels.Portuguese Foundation for Science and Technology (FCT/MCTES), under project PEst-OE/EEI/UI0066/2011, and to the CTS multiannual funding, through the PIDDAC Program funds. I am also very grateful for the grant SFRH/PROTEC/67683/2010, financially supported by the IPL – Instituto Politécnico de Lisboa