1,534 research outputs found
Capacitor Mismatch Calibration Technique to Improve the SFDR of 14-Bit SAR ADC
This paper presents mismatch calibration technique to improve the SFDR in a 14-bit successive approximation register (SAR) analog-to-digital converter (ADC) for wearable electronics application. Behavioral Monte-Carlo simulations are applied to demonstrate the effect of the proposed method where no complex digital calibration algorithm or auxiliary calibration DAC needed. Simulation results show that with a mismatch error typical of modern technology, the SFDR is enhanced by more than 20 dB with the proposed technique for a 14-bit SAR ADC
Design of the 12-bit Delta-Sigma Modulator using SC Technique for Vibration Sensor Output Processing
The work deals with the design of the 12-bit Delta-Sigma modulator using switched capacitors (SC) technique. The modulator serves to vibration sensor output processing. The first part describes the Delta-Sigma modulator parameters definition. Results of the proposed topology ideal model were presented as well. Next, the Delta-Sigma modulator circuitry on the transistor level was done. The ONSemiconductor I2T100 0.7 um CMOS technology was used for design. Then, the Delta-Sigma modulator nonidealities were simulated and implemented into the MATLAB ideal model of the modulator. The model of real Delta-Sigma modulator was derived. Consequently, modulator coefficients were optimized. Finally, the corner analysis of the Delta-Sigma modulator with the optimized coefficients was simulated. The value of SNDR = 82.2 dB (ENOB = 13.4 bits) was achieved
A Wearable Backscattering Modulator and RF Energy Harvester for UHF RFID Applications
To enable remote, battery-free, and wearable health-care, ultra-low-power and highly-efficient energy harvesting and communication front-ends are required. This paper presents the design and implementation of a wearable backscattering modulator and RF energy harvester for UHF RFID applications, which represents the first textile-based RFID modulator. The measured performance of the modulator is characterized using s-parameters and is shown successfully communicating with a commercial RFID reader using a textile antenna, suitable for integration in a fabric bandage. The rectifier's efficiency is also presented, in presence of the modulator, showing a high RF to DC efficiency exceeding 50%. This work lays the foundation for UHF RFID-powered smart bandages for next generation healthcare applications
Sensores passivos alimentados por transmissão de energia sem fios para aplicações de Internet das coisas
Nowadays, the Wireless Sensor Networks (WSNs) depend on the battery
duration of the sensors and there is a renewed interest in creating a passive
sensor network scheme in the area of Internet of Things (IoT) and space
oriented WSN systems. The challenges for the future of radio communications
have a twofold evolution, one being the low power consumption
and, another, the adaptability and intelligent use of the available resources.
Specially designed radios should be used to reduce power consumption, and
adapt to the environment in a smart and e cient way. This thesis will focus
on the development of passive sensors based on low power communication
(backscatter) with Wireless Power Transfer (WPT) capabilities used in IoT
applications. In that sense, several high order modulations for the communication
will be explored and proposed in order to increase the data rate.
Moreover, the sensors need to be small and cost e ective in order to be
embedded in other technologies or devices. Consequently, the RF front-end
of the sensors will be designed and implemented in Monolithic Microwave
Integrated Circuit (MMIC).Atualmente, as redes de sensores sem fios dependem da duração da bateria
e,deste modo, existe um interesse renovado em criar um esquema de rede
de sensores passivos na área de internet das coisas e sistemas de redes
de sensores sem fios relacionados com o espaço. Os desafios do futuro
das comunicações de rádio têm uma dupla evolução, sendo um o baixo
consumo de energia e, outro, a adaptação e o uso inteligente dos recursos
disponíveis. Rádios diferentes dos convencionais devem ser usados para
reduzir o consumo de energia e devem adaptar-se ao ambiente de forma
inteligente e eficiente, de modo a que este use a menor quantidade de
energia possível para estabelecer a comunicação. Esta tese incide sobre o
desenvolvimento de sensores passivos baseados em comunicação de baixo
consumo energético (backscatter) com recurso a transmissão de energia sem
fios de modo a que possam ser usados em diferentes aplicações inseridas na
internet das coisas. Nesse sentido, várias modulações de alta ordem para a
comunicação backscatter serão exploradas e propostas com o objectivo de
aumentar a taxa de transmissão de dados. Além disso, os sensores precisam
de ser reduzidos em tamanho e económicos de modo a serem incorporados
em outras tecnologias ou dispositivos. Consequentemente, o front-end de
rádio frequência dos sensores será projetado e implementado em circuito
integrado de microondas monolítico.Programa Doutoral em Engenharia Eletrotécnic
Development of Photonic Crystal Fiber Based Gas/ Chemical Sensors
The development of highly-sensitive and miniaturized sensors that capable of
real-time analytes detection is highly desirable. Nowadays, toxic or colorless
gas detection, air pollution monitoring, harmful chemical, pressure, strain,
humidity, and temperature sensors based on photonic crystal fiber (PCF) are
increasing rapidly due to its compact structure, fast response and efficient
light controlling capabilities. The propagating light through the PCF can be
controlled by varying the structural parameters and core-cladding materials, as
a result, evanescent field can be enhanced significantly which is the main
component of the PCF based gas/chemical sensors. The aim of this chapter is to
(1) describe the principle operation of PCF based gas/ chemical sensors, (2)
discuss the important PCF properties for optical sensors, (3) extensively
discuss the different types of microstructured optical fiber based gas/
chemical sensors, (4) study the effects of different core-cladding shapes, and
fiber background materials on sensing performance, and (5) highlight the main
challenges of PCF based gas/ chemical sensors and possible solutions
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