39 research outputs found
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Small core FBG-based temperature compensated โsmartโ contact lens for effective intraocular pressure measurement
In this work, a small core, Fibre Bragg Grating (FBG)-based smart contact lens for intraocular pressure (IOP) measurement has been demonstrated. Further, an integral temperature compensation mechanism has been developed and included in the sensor design, allowing it to offer good long-term measurement capability while allowing for any local temperature fluctuations. The sensitivity of the device has been shown to be 12.9 p.m./mmHg, yielding good repeatability in tests carried out. Such a small core fibre, FBG-based smart contact lens shows significant potential for improving the management and therapy of glaucoma, the second most common cause of preventable blindness in the world
Recent Advances on Implantable Wireless Sensor Networks
Implantable electronic devices are undergoing a miniaturization age, becoming more efficient and yet more powerful as well. Biomedical sensors are used to monitor a multitude of physiological parameters, such as glucose levels, blood pressure and neural activity. A group of sensors working together in the human body is the main component of a body area network, which is a wireless sensor network applied to the human body. In this chapter, applications of wireless biomedical sensors are presented, along with state-of-the-art communication and powering mechanisms of these devices. Furthermore, recent integration methods that allow the sensors to become smaller and more suitable for implantation are summarized. For individual sensors to become a body area network (BAN), they must form a network and work together. Issues that must be addressed when developing these networks are detailed and, finally, mobility methods for implanted sensors are presented
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A microscale optical implant for continuous in vivo monitoring of intraocular pressure
Intraocular pressure (IOP) is a key clinical parameter in glaucoma management. However, despite the potential utility of daily measurements of IOP in the context of disease management, the necessary tools are currently lacking, and IOP is typically measured only a few times a year. Here we report on a microscale implantable sensor that could provide convenient, accurate, on-demand IOP monitoring in the home environment. When excited by broadband near-infrared (NIR) light from a tungsten bulb, the sensorโs optical cavity reflects a pressure-dependent resonance signature that can be converted to IOP. NIR light is minimally absorbed by tissue and is not perceived visually. The sensorโs nanodot-enhanced cavity allows for a 3โ5โcm readout distance with an average accuracy of 0.29โmmโHg over the range of 0โ40โmmโHg. Sensors were mounted onto intraocular lenses or silicone haptics and secured inside the anterior chamber in New Zealand white rabbits. Implanted sensors provided continuous in vivo tracking of short-term transient IOP elevations and provided continuous measurements of IOP for up to 4.5 months
Inductively Coupled Split Ring Resonator as Small RFID Pressure Sensor for Biomedical Applications
We present an inductively coupled split-ring resonator based small passive RFID pressure sensor for wireless intracranial pressure measurement. The proposed sensor has a volume as small as ฯร(4 mm) 2 ร1 mm. In the simulation, the proposed sensor can provide nearly 1 m operation distance when implanted in the intracranial environment. In our preliminary measurement in the air, the sensor has a resolution of 3 cmH2O.acceptedVersionPeer reviewe
An Energy-Efficient Bridge-to-Digital Converter for Implantable Pressure Monitoring Systems
This paper presents an energy-efficient, duty-cycled, and spinning excitation bridge-to-digital converter (BDC) designed for implantable pressure sensing systems. The circuit provides the measure of the pulmonary artery pressure that is particularly relevant for the monitoring of heart failure and pulmonary hypertension patients. The BDC is made of a piezoresistive pressure sensor and a readout integrated circuit (IC) that comprises an instrumentation amplifier (IA) followed by an analog-to-digital converter (ADC). The proposed design spins both the bridge excitation and the ADCโs sampling input voltages simultaneously and exploits duty cycling to reduce the static power consumption of the bridge sensor and IA while cancelling the IAโs offset and 1/f noise at the same time. The readout IC has been designed and fabricated in a standard 180-nm CMOS process and achieves 8.4 effective number of bits (ENOB) at 1 kHz sampling rate while drawing 0.53 ยตA current from a 1.2 V supply. The BDC, built with the readout IC and a differential pressure sensor having 5 kฮฉ bridge resistances, achieves 0.44 mmHg resolution in a 270 mmHg pressure range at 1 ms conversion time. The current consumption of the bridge sensor by employing duty cycling is reduced by 99.8% thus becoming 0.39 ยตA from a 1.2 V supply. The total conversion energy of the pressure sensing system is 1.1 nJ, and achieves a figure-of-merit (FoM) of 3.3 pJ/conversion, which both represent the state of the art
An Ultra-Low-Power RFID/NFC Frontend IC Using 0.18 ฮผm CMOS Technology for Passive Tag Applications
Battery-less passive sensor tags based on RFID or NFC technology have achieved much popularity in recent times. Passive tags are widely used for various applications like inventory control or in biotelemetry. In this paper, we present a new RFID/NFC frontend IC (integrated circuit) for 13.56 MHz passive tag applications. The design of the frontend IC is compatible with the standard ISO 15693/NFC 5. The paper discusses the analog design part in details with a brief overview of the digital interface and some of the critical measured parameters. A novel approach is adopted for the demodulator design, to demodulate the 10% ASK (amplitude shift keying) signal. The demodulator circuit consists of a comparator designed with a preset offset voltage. The comparator circuit design is discussed in detail. The power consumption of the bandgap reference circuit is used as the load for the envelope detection of the ASK modulated signal. The sub-threshold operation and low-supply-voltage are used extensively in the analog design—to keep the power consumption low. The IC was fabricated using 0.18 μ m CMOS technology in a die area of 1.5 mm × 1.5 mm and an effective area of 0.7 m m 2 . The minimum supply voltage desired is 1.2 V, for which the total power consumption is 107 μ W. The analog part of the design consumes only 36 μ W, which is low in comparison to other contemporary passive tags ICs. Eventually, a passive tag is developed using the frontend IC, a microcontroller, a temperature and a pressure sensor. A smart NFC device is used to readout the sensor data from the tag employing an Android-based application software. The measurement results demonstrate the full passive operational capability. The IC is suitable for low-power and low-cost industrial or biomedical battery-less sensor applications. A figure-of-merit (FOM) is proposed in this paper which is taken as a reference for comparison with other related state-of-the-art researches
12.8 kHz Energy-Efficient Read-Out IC for High Precision Bridge Sensor Sensing System
ํ์๋
ผ๋ฌธ(๋ฐ์ฌ) -- ์์ธ๋ํ๊ต๋ํ์ : ๊ณต๊ณผ๋ํ ์ ๊ธฐยท์ ๋ณด๊ณตํ๋ถ, 2022.2. ๊น์ํ.In the thesis, a high energy-efficient read-out integrated circuit (read-out IC) for a high-precision bridge sensor sensing system is proposed. A low-noise capacitively-coupled chopper instrumentation amplifier (CCIA) followed by a high-resolution incremental discrete-time delta-sigma modulator (DTฮฮฃฮ) analog-to-digital converter (ADC) is implemented. To increase energy-efficiency, CCIA is chosen, which has the highest energy-efficiency among IA types. CCIA has a programmable gain of 1 to 128 that can amplify the small output of the bridge sensor. Impedance boosting loop (IBL) is applied to compensate for the low input impedance, which is a disadvantage of a CCIA. Also, the sensor offset cancellation technique was applied to CCIA to eliminate the offset resulting from the resistance mismatch of the bridge sensor, and the bridge sensor offset from -350 mV to 350 mV can be eliminated. In addition, the output data rate of the read-out IC is designed to be 12.8 kHz to quickly capture data and to reduce the power consumption of the sensor by turning off the sensor and read-out IC for the rest of the time. Generally, bridge sensor system is much slower than 12.8 kHz. To suppress 1/f noise, system level chopping and correlated double sampling (CDS) techniques are used. Implemented in a standard 0.13-ฮผm CMOS process, the ROICโs effective resolution is 17.0 bits at gain 1 and that of 14.6 bits at gain 128. The analog part draws the average current of 139.4 ฮผA from 3-V supply, and 60.2 ฮผA from a 1.8 V supply.๋ณธ ๋
ผ๋ฌธ์์๋ ๊ณ ์ ๋ฐ ๋ธ๋ฆฌ์ง ์ผ์ ์ผ์ฑ ์์คํ
์ ์ํ ์๋์ง ํจ์จ์ด ๋์ Read-out Integrated Circuit (read-out IC)๋ฅผ ์ ์ํ๋ค. ์ ์ก์ Capacitively-Coupled Instrumentation Amplifier (CCIA)์ ์ด์ ๊ณ ํด์๋ Discrete-time Delta-Sigma ๋ณ์กฐ๊ธฐ(DTฮฮฃฮ) ์๋ ๋ก๊ทธ-๋์งํธ ๋ณํ๊ธฐ(ADC)๋ฅผ ๊ตฌํํ์๋ค.
์๋์ง ํจ์จ์ ๋์ด๊ธฐ ์ํด IA ์ ํ ์ค ์๋์ง ํจ์จ์ด ๊ฐ์ฅ ๋์ CCIA๋ฅผ ์ ํํ์๋ค. CCIA๋ ๋ธ๋ฆฌ์ง ์ผ์์ ์์ ์ถ๋ ฅ์ ์ฆํญํ ์ ์๋ 1 ์์ 128์ ํ๋ก๊ทธ๋๋ฐ ๊ฐ๋ฅํ ์ ์ ์ด๋์ ๊ฐ์ง๋ค. CCIA์ ๋จ์ ์ธ ๋ฎ์ ์
๋ ฅ ์ํผ๋์ค๋ฅผ ๋ณด์ํ๊ธฐ ์ํด Impedance Boosting Loop (IBL)์ ์ ์ฉํ์๋ค. ๋ํ CCIA์ ์ผ์ ์คํ์
์ ๊ฑฐ ๊ธฐ์ ์ ์ ์ฉํ์ฌ ๋ธ๋ฆฌ์ง ์ผ์์ ์ ํญ ๋ฏธ์ค๋งค์น๋ก ์ธํ ์คํ์
์ ์ ๊ฑฐ ๊ธฐ๋ฅ์ ํ์ฌํ์์ผ๋ฉฐ -350mV์์ 350mV๊น์ง ๋ธ๋ฆฌ์ง ์ผ์ ์คํ์
์ ์ ๊ฑฐํ ์ ์๋ค. Read-out IC์ ์ถ๋ ฅ ๋ฐ์ดํฐ ์ ์ก๋ฅ ์ 12.8kHz๋ก ์ค๊ณํ์ฌ ๋ฐ์ดํฐ๋ฅผ ๋น ๋ฅด๊ฒ ์ฑ๊ณ ๋๋จธ์ง ์๊ฐ ๋์ ์ผ์์ read-out IC๋ฅผ ๊บผ์ ์ผ์์ ์ ๋ ฅ ์๋น๋ฅผ ์ค์ผ ์ ์๋๋ก ์ค๊ณํ์๋ค. ์ผ๋ฐ์ ์ผ๋ก ๋ธ๋ฆฌ์ง ์ผ์ ์์คํ
์ 12.8kHz๋ณด๋ค ๋๋ฆฌ๊ธฐ ๋๋ฌธ์ ์ด๊ฒ์ด ๊ฐ๋ฅํ๋ค. ํ์ง๋ง, ์ผ๋ฐ์ ์ธ CCIA๋ ์
๋ ฅ ์ํผ๋์ค ๋๋ฌธ์ ๋น ๋ฅธ ์๋์์ ์ค๊ณ๊ฐ ๋ถ๊ฐ๋ฅํ๋ค. ์ด๋ฅผ ํด๊ฒฐํ๊ธฐ ์ํด demodulate ์ฐจํ์ ์ฐํ ๋ด๋ถ๊ฐ ์๋ ์์คํ
์ฐจํ์ ์ด์ฉํด ํด๊ฒฐํ์๋ค.
1/f ๋
ธ์ด์ฆ๋ฅผ ์ต์ ํ๊ธฐ ์ํด ์์คํ
๋ ๋ฒจ ์ฐจํ ๋ฐ ์๊ด ์ด์ค ์ํ๋ง(CDS) ๊ธฐ์ ์ด ์ฌ์ฉ๋์๋ค. 0.13ฮผm CMOS ๊ณต์ ์์ ๊ตฌํ๋ read-out IC์ Effective Resolution (ER)์ ์ ์ ์ด๋ 1์์ 17.0๋นํธ์ด๊ณ ์ ์ ์ด๋ 128์์ 14.6๋นํธ๋ฅผ ๋ฌ์ฑํ์๋ค. ์๋ ๋ก๊ทธ ํ๋ก๋ 3 V ์ ์์์ 139.4ฮผA์ ํ๊ท ์ ๋ฅ๋ฅผ, ๋์งํธ ํ๋ก๋ 1.8 V ์ ์์์ 60.2ฮผA์ ํ๊ท ์ ๋ฅ๋ฅผ ์ฌ์ฉํ๋ค.CHAPTER 1 INTRODUCTION 1
1.1 SMART DEVICES 1
1.2 SMART SENSOR SYSTEMS 4
1.3 WHEATSTONE BRIDGE SENSOR 5
1.4 MOTIVATION 8
1.5 PREVIOUS WORKS 10
1.6 INTRODUCTION OF THE PROPOSED SYSTEM 14
1.7 THESIS ORGANIZATION 16
CHAPTER 2 SYSTEM OVERVIEW 17
2.1 SYSTEM ARCHITECTURE 17
CHAPTER 3 IMPLEMENTATION OF THE CCIA 19
3.1 CAPACITIVELY-COUPLED CHOPPER INSTRUMENTATION AMPLIFIER 19
3.2 IMPEDANCE BOOSTING 22
3.3 SENSOR OFFSET CANCELLATION 25
3.4 AMPLIFIER OFFSET CANCELLATION 29
3.5 AMPLIFIER IMPLEMENTATION 32
3.6 IMPLEMENTATION OF THE CCIA 35
CHAPTER 4 INCREMENTAL ฮฮฃ ADC 37
4.1 INTRODUCTION OF INCREMENTAL ฮฮฃ ADC 37
4.2 IMPLEMENTATION OF INCREMENTAL ฮฮฃ MODULATOR 40
CHAPTER 5 SYSTEM-LEVEL DESIGN 43
5.1 DIGITAL FILTER 43
5.2 SYSTEM-LEVEL CHOPPING & TIMING 46
CHAPTER 5 MEASUREMENT RESULTS 48
6.1 MEASUREMENT SUMMARY 48
6.2 LINEARITY & NOISE MEASUREMENT 51
6.3 SENSOR OFFSET CANCELLATION MEASUREMENT 57
6.4 INPUT IMPEDANCE MEASUREMENT 59
6.5 TEMPERATURE VARIATION MEASUREMENT 63
6.6 PERFORMANCE SUMMARY 66
CHAPTER 7 CONCLUSION 68
APPENDIX A. 69
ENERGY-EFFICIENT READ-OUT IC FOR HIGH-PRECISION DC MEASUREMENT SYSTEM WITH IA POWER REDUCTION TECHNIQUE 69
BIBLIOGRAPHY 83
ํ๊ธ์ด๋ก 87๋ฐ
Integrated Electronics for Wireless Imaging Microsystems with CMUT Arrays
Integration of transducer arrays with interface electronics in the form of single-chip CMUT-on-CMOS has emerged into the field of medical ultrasound imaging
and is transforming this field. It has already been used in several commercial products such as handheld full-body imagers and it is being implemented by commercial and academic groups for Intravascular Ultrasound and Intracardiac Echocardiography. However, large attenuation of ultrasonic waves transmitted through
the skull has prevented ultrasound imaging of the brain. This research is a prime
step toward implantable wireless microsystems that use ultrasound to image the
brain by bypassing the skull. These microsystems offer autonomous scanning
(beam steering and focusing) of the brain and transferring data out of the brain for
further processing and image reconstruction.
The objective of the presented research is to develop building blocks of an integrated electronics architecture for CMUT based wireless ultrasound imaging systems while providing a fundamental study on interfacing CMUT arrays with their
associated integrated electronics in terms of electrical power transfer and acoustic
reflection which would potentially lead to more efficient and high-performance
systems.
A fully wireless architecture for ultrasound imaging is demonstrated for the
first time. An on-chip programmable transmit (TX) beamformer enables phased
array focusing and steering of ultrasound waves in the transmit mode while its
on-chip bandpass noise shaping digitizer followed by an ultra-wideband (UWB)
uplink transmitter minimizes the effect of path loss on the transmitted image data
out of the brain. A single-chip application-specific integrated circuit (ASIC) is de-
signed to realize the wireless architecture and interface with array elements, each
of which includes a transceiver (TRX) front-end with a high-voltage (HV) pulser,
a high-voltage T/R switch, and a low-noise amplifier (LNA). Novel design techniques are implemented in the system to enhance the performance of its building
blocks.
Apart from imaging capability, the implantable wireless microsystems can include a pressure sensing readout to measure intracranial pressure. To do so, a
power-efficient readout for pressure sensing is presented. It uses pseudo-pseudo
differential readout topology to cut down the static power consumption of the sensor for further power savings in wireless microsystems.
In addition, the effect of matching and electrical termination on CMUT array
elements is explored leading to new interface structures to improve bandwidth
and sensitivity of CMUT arrays in different operation regions. Comprehensive
analysis, modeling, and simulation methodologies are presented for further investigation.Ph.D
Advances in Ophthalmology
This book focuses on the different aspects of ophthalmology - the medical science of diagnosis and treatment of eye disorders. Ophthalmology is divided into various clinical subspecialties, such as cornea, cataract, glaucoma, uveitis, retina, neuro-ophthalmology, pediatric ophthalmology, oncology, pathology, and oculoplastics. This book incorporates new developments as well as future perspectives in ophthalmology and is a balanced product between covering a wide range of diseases and expedited publication. It is intended to be the appetizer for other books to follow. Ophthalmologists, researchers, specialists, trainees, and general practitioners with an interest in ophthalmology will find this book interesting and useful