Amplifiers in Biomedical Engineering: A Review from Application Perspectives

Continuous monitoring and treatment of various diseases with biomedical technologies and wearable electronics has become significantly important. The healthcare area is an important, evolving field that, among other things, requires electronic and micro-electromechanical technologies. Designed circuits and smart devices can lead to reduced hospitalization time and hospitals equipped with high-quality equipment. Some of these devices can also be implanted inside the body. Recently, various implanted electronic devices for monitoring and diagnosing diseases have been presented. These instruments require communication links through wireless technologies. In the transmitters of these devices, power amplifiers are the most important components and their performance plays important roles. This paper is devoted to collecting and providing a comprehensive review on the various designed implanted amplifiers for advanced biomedical applications. The reported amplifiers vary with respect to the class/type of amplifier, implemented CMOS technology, frequency band, output power, and the overall efficiency of the designs. The purpose of the authors is to provide a general view of the available solutions, and any researcher can obtain suitable circuit designs that can be selected for their problem by reading this survey

Ultra-Low-Power Sensors and Receivers for IoT Applications

The combination of ultra-low power analog front-ends and CMOS-compatible transducers enable new applications, such as environmental monitors, household appliances, health trackers, etc. that are seamlessly integrated into our daily lives. Furthermore, wireless connectivity allows many of these sensors to operate both independently and collectively. These techniques collectively fulfil the recent surge of internet-of-things (IoT) applications that have the potential to fundamentally change daily life for millions of people.In this dissertation, the circuit and system design of wireless receivers and sensors is presented that explores the challenges of implementing long lifespan, high accuracy, and large coverage range IoT sensor networks. The first is a wake-up receiver (WuRX), which continuously monitors the RF environment to wake up a higher-power radio upon detection of a predetermined RF signature. This work both improves sensitivity and reduces power over prior art through a multi-faceted design featuring an impedance transformation network with large passive voltage gain, an active envelope detector with high input impedance to facilitate large passive voltage gain, a low-power precision comparator, and a low-leakage digital baseband correlator.Although pushing the prior WuRX performance boundary by orders of magnitude, the first work shows moderate sensitivity, inferior temperature robustness, and large area with external lumped components. Thus, the second work shows a miniaturized WuRX that is temperature-compensated, yet still consumes only nano-watt power and millimeter area while operating at 9 GHz. To further reduce the area, a global common-mode feedback is utilized across the envelope detector and baseband amplifier that eliminates the need for off-chip ac-coupling components. Multiple temperature-compensation techniques are proposed to maintain constant bandwidth of the signal path and constant clock frequency. Both WuRXs operate at 0.4 V supply, consume near-zero power and achieve ~-70 dBm sensitivity.Lastly, the first reported CMOS 2-in-1 relative humidity and temperature sensor is presented. A unified analog front-end interfaces on-chip transducers and converts the inputs into a frequency vis a high-linearity frequency-locked loop. An incomplete-settling switched-capacitor-based Wheatstone bridge is proposed to sense the inputs in a power-efficient fashion

Interface Circuits for Microsensor Integrated Systems

ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Recent advances in sensing technologies, especially those for Microsensor Integrated Systems, have led to several new commercial applications. Among these, low voltage and low power circuit architectures have gained growing attention, being suitable for portable long battery life devices. The aim is to improve the performances of actual interface circuits and systems, both in terms of voltage mode and current mode, in order to overcome the potential problems due to technology scaling and different technology integrations. Related problems, especially those concerning parasitics, lead to a severe interface design attention, especially concerning the analog front-end and novel and smart architecture must be explored and tested, both at simulation and prototype level. Moreover, the growing demand for autonomous systems gets even harder the interface design due to the need of energy-aware cost-effective circuit interfaces integrating, where possible, energy harvesting solutions. The objective of this Special Issue is to explore the potential solutions to overcome actual limitations in sensor interface circuits and systems, especially those for low voltage and low power Microsensor Integrated Systems. The present Special Issue aims to present and highlight the advances and the latest novel and emergent results on this topic, showing best practices, implementations and applications. The Guest Editors invite to submit original research contributions dealing with sensor interfacing related to this specific topic. Additionally, application oriented and review papers are encouraged.

Design of agile signal conditioning circuits for microelectromechanical sensors

Microelectromechanical systems (MEMS) are used in many applications to detect physical parameters and convert them to an electrical signal. The output of MEMS-based transducers is usually not suitable to be directly processed in the digital or the analog domain, and they could be as small as femto farads in capacitive sensing and micro volts in resistive sensing. Consequently, high sensitivity signal conditioning circuits are essential. In this thesis, it is shown that both the noise and input capacitance are important parameters to ensure optimal capacitive sensing. The dominant noise source in MEMS conditioning circuits is flicker noise, and one of the best methods to mitigate flicker noise is the chopping technique. Three different chopping techniques are considered: single chopper amplifier (SCA), dual chopper amplifier (DCA), and two-stage single chopper amplifier (TCA). Also, their sensitivity and power consumption based on the total gain and sensing capacitance are extracted. It is shown that the distribution of gain between the two stages in the DCA and TCA has a significant effect on the sensitivity, and, based on this distribution, the sensitivity and power consumption change significantly. For small sensor capacitances, the highest sensitivity could be achieved by a DCA because of its ability to decrease the noise floor and the input sensor capacitance simultaneously. A novel DCA is proposed to reach higher sensitivity and reduced power consumption. In this DCA, two supply voltages are utilized, and the second stage is composed of two parallel paths that improve the SNR and provide two gain settings. This circuit is fabricated in the GlobalFoundries 0.13 μm CMOS technology. The measurement results show a power consumption of 2.66 μW for the supply voltage of 0.7 V and of 3.26 μW for the supply voltage of 1.2 V. The single path DCA has a gain of 34 dB with bandwidth of 4 kHz and input noise floor of 25 nV/√Hz. The dual path DCA has a gain of 38 dB with bandwidth of 3 kHz and input noise floor of 40 nV/√Hz. To be able to detect the signal near DC frequencies, another circuit is proposed which has a configurable bandwidth and a sub-μHz noise corner frequency. This circuit is composed of three stages, and three chopping frequencies are used to mitigate the flicker noise of the three stages. The simulated circuit is designed in the GlobalFoundries 0.13 μm CMOS technology with supply voltages of 0.4 V and 1.2 V. The total power consumption is of 6.7 μW. A gain of 68 dB and bandwidths of 1, 10, 100 and 1000 Hz are achieved. The input referred noise floor is of 20.5 nV/√Hz and the design attains a good power efficiency factor of 4.0. In the capacitive mode, the noise floor is of 3.6 zF for a 100 fF capacitance sensor

Microelectromechanical Systems for Wireless Radio Front-ends and Integrated Frequency References.

Microelectromechanical systems (MEMS) have great potential in realizing chip-scale integrated devices for energy-efficient analog spectrum processing. This thesis presents the development of a new class of MEMS resonators and filters integrated with CMOS readout circuits for RF front-ends and integrated timing applications. Circuit-level innovations coupled with new device designs allowed for realizing integrated systems with improved performance compared to standalone devices reported in the literature. The thesis is comprised of two major parts. The first part of the thesis is focused on developing integrated MEMS timing devices. Fused silica is explored as a new structural material for fabricating high-Q vibrating micromechanical resonators. A piezoelectric-on-silica MEMS resonator is demonstrated with a high Q of more than 20,000 and good electromechanical coupling. A low phase noise CMOS reference oscillator is implemented using the MEMS resonator as a mechanical frequency reference. Temperature-stable operation of the MEMS oscillator is realized by ovenizing the platform using an integrated heater. In an alternative scheme, the intrinsic temperature sensitivity of MEMS resonators is utilized for temperature sensing, and active compensation for MEMS oscillators is realized by oven-control using a phase-locked loop (PLL). CMOS circuits are implemented for realizing the PLL-based low-power oven-control system. The active compensation technique realizes a MEMS oscillator with an overall frequency drift within +/- 4 ppm across -40 to 70 °C, without the need for calibration. The CMOS PLL circuits for oven-control is demonstrated with near-zero phase noise invasion on the MEMS oscillators. The properties of PLL-based compensation for realizing ultra-stable MEMS frequency references are studied. In the second part of the thesis, RF MEMS devices, including tunable capacitors, high-Q inductors, and ohmic switches, are fabricated using a surface micromachined integrated passive device (IPD) process. Using this process, an integrated ultra-wideband (UWB) filter has been demonstrated, showing low loss and a small form factor. To further address the issue of narrow in-band interferences in UWB communication, a tunable MEMS bandstop filter is integrated with the bandpass filter with more than an octave frequency tuning range. The bandstop filter can be optionally switched off by employing MEMS ohmic switches co-integrated on the same chip.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/109069/1/zzwu_1.pd

Differential absorption lidars for remote sensing of atmospheric pressure and temperature profiles

A near infrared differential absorption lidar technique is developed using atmospheric oxygen as a tracer for high resolution vertical profiles of pressure and temperature with high accuracy. Solid-state tunable lasers and high-resolution spectrum analyzers are developed to carry out ground-based and airborne measurement demonstrations and results of the measurements presented. Numerical error analysis of high-altitude airborne and spaceborne experiments is carried out, and system concepts developed for their implementation

Robust low power CMOS methodologies for ISFETs instrumentation

I have developed a robust design methodology in a 0.18 [Mu]m commercial CMOS process to circumvent the performance issues of the integrated Ions Sensitive Field Effect Transistor (ISFET) for pH detection. In circuit design, I have developed frequency domain signal processing, which transforms pH information into a frequency modulated signal. The frequency modulated signal is subsequently digitized and encoded into a bit-stream of data. The architecture of the instrumentation system consists of a) A novel front-end averaging amplifier to interface an array of ISFETs for converting pH into a voltage signal, b) A high linear voltage controlled oscillator for converting the voltage signal into a frequency modulated signal, and c) Digital gates for digitizing and differentiating the frequency modulated signal into an output bit-stream. The output bit stream is indistinguishable to a 1st order sigma delta modulation, whose noise floor is shaped by +20dB/decade. The fabricated instrumentation system has a dimension of 1565 [Mu] m 1565 [Mu] m. The chip responds linearly to the pH in a chemical solution and produces a digital output, with up to an 8-bit accuracy. Most importantly, the fabricated chips do not need any post-CMOS processing for neutralizing any trapped-charged effect, which can modulate on-chip ISFETs’ threshold voltages into atypical values. As compared to other ISFET-related works in the literature, the instrumentation system proposed in this thesis can cope with the mismatched ISFETs on chip for analogue-to-digital conversions. The design methodology is thus very accurate and robust for chemical sensing

Trace gas detection and high-precision spectroscopy in the mid-infrared and visible wavelength regions

This thesis is based on four experimental spectroscopic studies where novel highly sensitive laser absorption spectroscopy spectrometers are developed and used for trace gas detection and precision spectroscopy. Most of the studies are carried out in the mid-infrared region between 3 and 4 µm, where a homebuilt continuous-wave singly resonating optical parametric oscillator is used as a light source. In addition, one study has been performed in the visible region using a commercial green laser at 532 nm. Two of the developed spectroscopic applications are based on cavity ring-down spectroscopy. In this thesis, the first off-axis re-entrant cavity ring-down spectrometer in the mid-infrared is demonstrated and utilized for highly sensitive detection of formaldehyde. The second study presents an optical frequency comb referenced mid-infrared continuous-wave singly resonating optical parametric oscillator, which is applied to high-precision cavity ring-down spectroscopy of nitrous oxide and methane. Furthermore, this study presents a new method for referencing a mid-infrared optical parametric oscillator to a near-infrared optical frequency comb. This new method allows large mode-hop-free frequency tuning ranges in the mid-infrared region. The other two experiments are based on cantilever-enhanced photoacoustic spectroscopy, presenting the first reported studies of cantilever-enhanced-based trace gas detection in the mid-infrared and visible region. These studies show the great potential of cantilever-enhanced photoacoustic detection for substantial enhancement of the sensitivity of trace gas detection. For instance, the best nitrogen dioxide detection limit ever reported using photoacoustic spectroscopy is presented in this thesis.Tämä väitöskirja sisältää neljä laserspektroskopiaan perustuvaa kokeellista tutkimusta. Tutkimuksissa on kehitetty uusia, korkeaan spektroskooppiseen erotuskykyyn ja suureen herkkyyteen perustuvia mittausmenetelmiä ja mittalaitteita ympäristön kannalta tärkeiden, pienimolekyylisten kaasutilassa esiintyvien yhdisteiden (hivenkaasujen) havaitsemiseksi. Tällaisia hivenkaasuja ovat mm. dityppioksidi (N2O), formaldehydi (CH2O), metaani (CH4), typpidioksidi (NO2) ja vetysyanidi (HCN), joista esimerkiksi CH4 ja N2O ovat ilmastonmuutoksen ja CH2O sisäilman laadun kannalta tärkeitä yhdisteitä. Lisäksi autojen polttomoottorit ja voimalaitokset tuottavat ilmakehään mm. haitallisia typen oksideita, kuten NO2:ta. Kyseisten hivenkaasujen suhteelliset pitoisuudet näytematriisissa (esim. ilmakehässä) ovat tyypillisesti erittäin pieniä (miljoonas-, miljardis- tai jopa biljoonasosia), joten niiden havaitsemiseen tarvitaan erittäin herkkiä mittausmenetelmiä. Laserspektroskopialla on mahdollista havaita (''haistaa'') näitä yhdisteitä herkästi ja usein myös reaaliaikaisesti. Etenkin keski-infrapuna-alueella eli niin kutsutulla sormenjälkialueella, jossa sijaitsee esimerkiksi useimpien hiilivetyjen voimakkaimmat absorptiot. Väitöskirjassa kehitetyt spektrometrit on toteutettu yhtä lukuun ottamatta keski-infrapuna-alueella ja ne perustuvat ontelovaimenemisspektroskopiaan sekä valoakustiseen spektroskopiaan. Tässä väitöskirjassa kehitettiin keski-infrapuna-alueen ei-aksiaalinen ontelovaimenemisspektrometri formaldehydille, joka mahdollistaa alle sadan miljardisosan suhteellisten formaldehydipitoisuuksien nopean mittaamisen. Tässä väitöskirjassa kehitettiin myös yhteistyössä mittatekniikankeskuksen (MIKES-VTT Oy) kanssa uudenlainen ontelovaimenemisspektrometri, jolla on mahdollista määrittää molekyylien, kuten dityppioksidin ja metaanin absorptiovoimakkuuksia ja niiden keskitaajuuksia absoluuttisen tarkasti (jäljitettävästi) sormenjälkialueella. Näitä perustutkimuksenkin kannalta tärkeitä spektroskooppisia määreitä voidaan hyödyntää mm. ilmastonmuutoksen mallinnuksessa. Lisäksi tässä väitöskirjassa kehitettiin yhteistyössä Gasera Oy:n kanssa valoakustiseen spektroskopiaan perustuva mittalaite HCN:lle ja CH4:lle, sekä mittalaite ympäristölle haitalliselle, erityisesti dieselmoottoreissa syntyvälle typpidioksidille. Tässä väitöskirjassa saavutettu 50:n biljoonasosan suhteellinen havaintoraja NO2:lle on pienin koskaan raportoitu tulos käyttäen valoakustista spektroskopiaa. Kyseinen NO2-tutkimus toteutettiin muista tutkimuksista poiketen näkyvän valon alueella. Tässä väitöskirjatyössä kehitettyjen laserspektroskopiaan perustuvien menetelmien ja mittalaitteiden erinomainen herkkyys perustuu ulkoisten optisten onteloiden tarjoamaan pitkään absorptiomatkaan sekä valoakustisen signaalin uudenlaiseen mittaamiseen erittäin herkällä piiliuskalla (''optinen mikrofoni''), ja erityisesti näiden kahden menetelmän yhdistämiseen ensimmäistä kertaa keski-infrapuna-alueen ja näkyvän valon alueen lasereiden kanssa. Kyseiset menetelmät eivät sovellu ainoastaan yllä mainituille yhdisteille, vaan niitä on mahdollista soveltaa myös muiden ilmakehässä esiintyvien sekä ihmisen että luonnon emittoimien pienimolekyylisten kaasujen havainnointiin etenkin keski-infrapuna-alueella

Applications Technology Satellite ATS-6 experiment checkout and continuing spacecraft evaluation report

The activities of the ATS-6 spacecraft are reviewed. The following subsystems and experiments are summarized: (1) radio beacon experiments; (2) spacecraft attitude precision pointing and slewing adaptive control experiment; (3) satellite instruction television experiment; (4) thermal control subsystem; (5) spacecraft propulsion subsystem; (6) telemetry and control subsystem; (7) millimeter wave experiment; and (8) communications subsystem. The results of performance evaluation of its subsystems and experiments are presented