Jahariah Sampe

Towards high performance graphene nanoribbon transistors (GNR-FETs)

We fabricated trilayer graphene nanoribbon (GNR) Field Effect Transistors (FETs) by means of mechanical exfoliation method and investigate the characteristics of the device. The device shows ambipolar operation with a good Ohmic contact between the graphene and electrodes. Arrhenius plots of temperature dependence of conductance are consistence with thermal activated conduction above 273 K, and variable range hopping conduction at low temperature. GNR charge carrier provides high electron mobility of 6198 cm2V-1s-1 at 273 K, and lower activation energy of 0.592 meV. This device possesses high performance and requires ultra-low power compare to other reported graphene-based transistors.

Optimization of RF- DC converter in micro energy harvester using voltage boosting network and bulk modulation technique for biomedical devices

This paper presents an optimization of the rectifier module for Radio Frequency (RF) energy harvesting system at 915 MHz band. This module converts the RF signal into direct-current voltage at the given frequency band to power ultra-low power bio-medical sensor. A transient analysis on various types of rectifier circuit is carried out to investigate their efficiency and sensitivity. To improve the power conversion efficiency, the voltage boosting network increases the voltage at the input of the full wave rectifier. By assuming the system is at resonance condition, the optimum parameters including the value of capacitance, inductance and load value are calculated. Simulation results show that passive component based circuit can significantly increase the RF input voltage and broaden the input range of the rectifier. The modified circuit enhances output voltage approximately 400 mV higher than output voltage from existing full wave rectifier at same level of input. This will help to increase the input range to be converted to dc output.

Parametric analysis of boost converter for energy harvesting using piezoelectric for micro devices

Lower amount of power delivered from piezoelectric based ambient vibration energy harvester devices is a barrier to adopt the technology for different applications. Energy harvesting circuitry can enhance power output to provide a regulated DC supply to the end application. In this paper, various circuit simulations are carried out to investigate output power enhancement. A parametric analysis of a boost circuit simulation using Cadence OrCAD Capture PSpice software with input less than 1 V is carried out to find the optimum parameters including, the switching frequency rise and fall times, duty cycle, inductance and load capacitance value. Simulation results show that passive component based boost converter can significantly increase the voltage output of an ambient vibration based energy harvester. The output voltage increases linearly with the increase of single supply voltage input range 0.1 V to 0.5 V, to the output voltage range of 7 to 35 V. The optimum parameter found for 10 kΩ load is 100 μH inductor and 1μF load capacitor. A comparison of output performance of the boost circuit with existing literature is presented. The ease of the boost converter circuit will facilitate the development of an efficient piezoelectric energy harvesters for low power applications like automotive, healthcare portable devices, and wireless sensor networks.

Numerical simulation of one dimensional (1D) photonic crystal multiple cavities based on silicon on insulator (SOI)

We have theoretically demonstrated the variation of geometrical parameters for the cavities design of one dimensional (1D) photonic crystal nanocavity based on silicon on insulator (SOI) waveguides. To evaluate the cavity numerically, we have successfully computed it using the 2D finite difference time domain (FDTD) approach. We have varied the geometrical hole size, lattice and number of cavity. We have also varied the length of the cavity parameter, from 530 to 675 nm and for lattice constant from 345 to 410 nm. The optimized quality factors of approximately 4300 at 1617.9 nm resonance wavelengths were obtained and the free spectral range (FSR) was calculated to be in the range of 10 to 60 nm.

Designing a boost converter of micro energy harvester using thermal and vibration input for biomedical devices

This work presents a designed of boost converter Hybrid Micro Energy Harvester (HMEH) using thermal and vibration of human body for biomedical application. Thermal converts temperature differences directly into electrical energy. While vibration is based on human movement like walking and shaking body that is able to generate an AC voltage. Having two sources overcome the limitation caused by a single source harvester and improves system functionality. The inputs are set to 0.2V, 0.3V and 0.5V to represent thermal, vibration and combination of thermal and vibration (hybrid) respectively. A rectifier is designed to convert vibration input from AC to DC voltages. The proposed boost converter is used to step-up the small input voltage from thermal and vibration at 2 kHz. The inductance is varied from 0.4μH to 1.2μH, 0.9μH to 2.9μH and 0.3μH to 0.9μH for vibration, thermal and hybrid input respectively. However, the optimize value for the designed is 0.9μH for all sources to achieve the regulated output of 2.0 to 4.0V. Both rectifier and boost converter circuit consist of MOSFET as the heart of the operation. In this paper, the circuits are designed, modeled and simulated using PSPICE software.

Higher Sensitivity RF-DC Rectifier for Ultra-Low Power Semi-Active RFID Tags

Radio frequency (RF) energy harvesting is the process where energy is captured from the radiated RF signals and converted it to electrical power to supply a very small amount of power to modern electronic devices. This paper presents a RF energy harvester for ultra-low power semi-active UHF radio frequency identification tag applications. The main objective is to solve the semi-active UHF RFID tag limited lifespan issues due to the need for batteries to power its circuitries.In this design, the energy from the radiated RF signals is converted to electrical power by a module known as RF-DC rectifier. The circuit is based on a cross-connected differential-drive CMOS rectifier topology which is implemented in 0.13 μm CMOS standard technology with the input RF power range from -20 dBm to -10 dBm operating in 915 MHz frequency band. To ensure a maximum output voltage is achieved, several simulations based on the optimized matching network components, the variation of transistor sizes and load resistance, and increases the number of rectifier stages are investigated. All the circuit designs and simulations are performed using Orcad Cadance software. The simulated results shown that the optimized impedance matching network and a six-stage cross-connected differential-drive CMOS rectifier circuit able to produces a 1.13 V DC output voltage with an input power of -10 dBm (100 μW) and 1 MΩ load resistance.The results obtained shows that the proposed design can extend the lifetime of semi-active UHF RFID tag, able to eliminate its dependency on battery and make it possible to achieve a batteryless tag. Therefore, can be used to supply electrical power continuously for RFID tag applications.

Schmitt Trigger based on Dual Output Current Controlled Current Conveyor in 16nm CMOS technology for digital applications

This paper presents a current mode Schmitt Trigger based on Dual Output Current Controlled Current Conveyor (DOCCCII). To overcome the frequency limitation and enable low voltage low power operation (LVLP) current mode circuits are generally preferred. They offer higher bandwidth, improved slew rate and better (LVLP) performance compared to their voltage mode counterparts. So for the design we have selected second generation current controlled current conveyor which is regarded as the universal current mode active building block. The circuit topology is very simple, its construction consists of a single DOCCCII and an inverter implemented in 16 nm bulk CMOS technology model parameters obtained from Predictive Technology Model (PTM) together with two resistors. The circuit is suitable for integration, it uses the supply voltage of ±0.8V and a bias current of 10μA. The performance of the proposed circuit is examined using H-Spice where the circuit exhibited the power dissipation of 57.78μW. The circuit performance is in agreement with the theoretical explanation. The noise removing capability of the circuit is presented here as an application.

Design and simulation of piezoelectric cantilever beam based on mechanical vibration for energy harvesting application

This paper presents design and simulation of a piezoelectric cantilever beam for energy harvesting using mechanical ambient vibration. Ambient vibration energy used by the developed piezoelectric cantilever beam can be converted into electrical energy using piezoelectric effect as a piezoelectric energy harvester. The piezoelectric cantilever beam was consisted of copper substrate, two piezoelectric layers, and a base. The two piezoelectric layers were placed at the top and bottom faces of the copper substrate. The 3D design of the beam was performed by using SolidWorks. The simulation of the piezoelectric harvester was performed by COMSOL Multiphysics where Finite Element Method (FEM) was used. During the analysis, mechanical and electrical properties of the energy harvester were analysed. In the mechanical properties analysis, maximum vertical displacement of 70.9 µm and maximum stress of 7.96×105 N/m2 were obtained at resonant frequency of 345.75 Hz. A maximum output power of 14.85 µw and voltage of 595.5 mV was obtained from the harvester at 12.6 kΩ under the acceleration of 1 g (g = 9.81 m/s2) at resonant frequency of 345.75 Hz. This energy harvester can be used for numerous purpose in the field of sensors and wireless sensor networks.

Reliable and cost effective anti-collision technique for RFID UHF tag

This paper presents a proposed Reliable and Cost Effective Anti-collision technique (RCEAT) for Radio Frequency Identification (RFID) Class 0 UHF tag. The RCEAT architecture consists of two main subsystems; PreRCEAT and PostRCEAT. The PreRCEAT subsystem is to detect any error in the incoming messages. Then the identification bit (ID) of the no error packet will be fed to the next subsystem. The PostRCEAT subsystem is to identify the tag by using the proposed Fast-search Lookup Table. The proposed system is designed using Verilog HDL. The system is simulated using Modelsim and synthesized using Xilinix Synthesis Technology. The system has been successfully implemented in hardware using Field Programmable Grid Array (FPGA) Virtex II. The output waveforms from the FPGA have been tested on the Tektronix Logic Analyzer for real time verification. Finally the RCEAT architecture is resynthesized using Application Specific Integrated Circuit (ASIC) technology for on-chip implementation. This technology consists of 0.18 μm Library, Synopsys Compiler and tools. From the hardware verification results, it shows that the proposed RCEAT system enables to identify the tags without error at the maximum operating frequency of 180MHz. The system consumes 7.578 mW powers, occupies 6,041 gates and 0.0375 mm2 area with Data arrival time of 2.31 ns.

Parameter design of microstrip patch antenna operating at dual microwave-band for RF energy harvester application

The growth innovation and versatility in wireless energy harvester have attracted an attention on the development of antennas. This paper presents microstrip patch antenna design of a dual-band radio frequency (RF) energy harvester system for self-powered devices. The antenna is designed using a slot-coupled structure to realize for dual microwave bands operation. By using an optimization parameter of 50Ω feed point on microstrip line, the proposed patch antenna has achieved good impedance matching. Parameter design of the feed point with the optimal extension length, ΔL improves the performance at targeted resonating frequencies. COMSOL Multiphysics 5.1 electromagnetic package is utilized for the simulation and analysis process. The proposed antenna provides good performance parameter in terms of radiation pattern and return loss. The simulated results indicate satisfactory return loss performance of −31.867 dB and −24.437 dB in the dual narrowband resonance frequencies at 1.9GHz and 2.45GHz respectively. This property of results can be employed in rectifier of RF energy harvester system.