Low Front Research Articles

A low noise front end electronics for micro-channel plate detector with wedge and strip anode

A low noise Front End Electronics (FEE) for two-dimensional position sensitive Micro-Channel Plate (MCP) detector has been developed. The MCP detector is based on Wedge and Strip Anode (WSA) with induction readout mode. The WSA has three electrodes, the wedge electrode, the strip electrode, and the zigzag electrode. Then, three readout channels are designed in the Printed Circuit Board (PCB). The FEE is calibrated by a pulse generator from Agilent. We also give an analysis of the charge loss from the CSA. The noise levels of the three channels are less than 1 fC RMS at the shaping time of 200 ns. The experimental result shows that the position resolution of the MCP detector coupled with the designed PCB can reach up to 110 μm.

Low Power Personalized ECG Based System Design Methodology for Remote Cardiac Health Monitoring

This paper describes a mixed-signal electrocardiogram (ECG) system for personalized and remote cardiac health monitoring. The novelty of this paper is fourfold. First, a low power analog front end with an efficient automatic gain control mechanism, maintaining the input of the ADC to a level rendering optimum SNR and the enhanced recyclic folded cascode opamp used as an integrator for $\Sigma \Delta $ ADC. Second, a novel on-the-fly PQRST boundary detection (BD) methodology is formulated for finding the boundaries in continuous ECG signal. Third, a novel low-complexity ECG feature extraction architecture is designed by reusing the same module present in the proposed BD methodology. Fourth, the system is having the capability to reconfigure the proposed low power ADC for low (8 b) and high (12 b) resolution with the use of the feedback signal obtained from the digital block when it is in processing. The proposed system has been tested and validated on patient’s data from PTBDB, CSEDB, and in-house IIT Hyderabad Data Base (IITHDB) and we have achieved an accuracy of 99% upon testing on various normal and abnormal ECG signals. The whole system is implemented in 180-nm technology resulting in 9.47- $\mu \text{W}$ (at 1 MHz) power consumption and occupying 1.74- $mm^{2}$ silicon area.

Optimal dipole planar antenna array design for different UHF band applications using cuckoo search algorithm

This article presents the cuckoo search algorithm (CSA) for the optimum design of a 4 × 4 dipole planar antenna array (DPAA) taking mutual coupling into account. The CSA is employed to optimise the input parameters such as lengths of each dipole elements and separation distance between the dipole elements of the DPAA in order to achieve higher directivity with low half power beam width and high front to side lobe level with less computational time. The optimal input parameters at 300 MHz are obtained using a multi-objective fitness function. The array is simulated using method of moments codes using MATLAB and verified using MININEC software. Finally, the optimised results are compared with the results of other antenna arrays obtained using several other popular optimisation techniques to evaluate the performance of our proposed DPAA. The optimum design procedure can be used to design similar DPAAs at other operating frequencies in the UHF band.

A low power low noise analog front end for portable healthcare system**Project supported by the Science and Technology Commission of Shanghai Municipality (No. 13511501100), the State Key Laboratory Project of China (No. 11MS002), and the State Key Laboratory of ASIC & System, Fudan University.

The presented analog front end (AFE) used to process human bio-signals consists of chopping instrument amplifier (IA), chopping spikes filter and programmable gain and bandwidth amplifier. The capacitor-coupling input of AFE can reject the DC electrode offset. The power consumption of current-feedback based IA is reduced by adopting capacitor divider in the input and feedback network. Besides, IA's input thermal noise is decreased by utilizing complementary CMOS input pairs which can offer higher transconductance. Fabricated in Global Foundry 0.35 μm CMOS technology, the chip consumes 3.96 μA from 3.3 V supply. The measured input noise is 0.85 μVrms (0.5–100 Hz) and the achieved noise efficient factor is 6.48.

Avaliação morfométrica de equinos do Esquadrão de Polícia Montada dos municípios de Lages, Joinville e Florianópolis-SC

RESUMOO objetivo do presente trabalho foi avaliar as características morfométricas de equinos utilizados no patrulhamento ostensivo pertencentes aos Esquadrões de Polícia Montada localizados nos municípios de Lages, Joinville e Florianópolis - SC. Foram utilizados 101 animais (78 machos castrados, um garanhão e 22 fêmeas), com idade média de 11,9 anos e massa corpórea de 490,82±53,51kg. Foram tomadas 20 medidas lineares individuais, por meio das quais foram determinados 13 índices zootécnicos. Os dados foram avaliados segundo análise descritiva, e a comparação simples entre médias pelo teste t de Student (P<0,05). Houve diferença significativa entre machos e fêmeas com relação ao comprimento de garupa, largura da anca, perímetro da canela e IDT nos animais pertencentes ao Esquadrão de Florianópolis. Conclui-se que os equinos dos três Esquadrões avaliados são, em geral, animais baixos de frente, "longe de terra", eumétricos e longilíneos, e classificados entre animais de tração ligeira e de tração pesada.

Analysis and optimization of In<sub>1-x</sub>GaxAsyBb<sub>1-y</sub> thermophotovoltaic cells under low radiator temperatures

In this paper,we investigated the heat to electricity conversion efficiency of In 1-x Ga x As y Sb 1-y radioisotope thermophotovoltaic (RTPV) converter with x=0.8 and y=0.18, taking account of the photons with energy below the cells bandgap using a comprehensive analytical process. This was done with a computer program designed for this reason, which allowed the computation of the cell performance under a variety of specified incident radiation spectra as well as a variety of material parameters. The results show that for an emissivity value of 0.78, a cell thickness of about 7µm with low front recombination velocity(700cm/s),a conversion efficiency greater than 29% can be obtained for radiator’s temperature of1300°k at ambient temperature. This efficiency will decrease as the cell temperature increase.

Transport of Surface Freshwater from the Equatorial to the Subtropical North Atlantic Ocean

AbstractThe transport of low-salinity water northward in the tropical and subtropical North Atlantic Ocean influences upper-ocean stratification, vertical mixing, and sea surface temperature (SST). In this study, satellite and in situ observations are used to trace low-salinity water northward from its source in the equatorial Atlantic and to examine its modification through air–sea fluxes and vertical mixing. In contrast to gridded climatologies, which depict a gradual northward dispersal of surface freshwater from the equatorial Atlantic, satellite observations and direct measurements from four moorings in the central tropical North Atlantic show a distinct band of surface freshwater moving northward from the equatorial Atlantic during boreal fall through spring, with drops in sea surface salinity (SSS) of 0.5–2.5 psu in the span of one to two weeks as the low SSS front passes. The ultimate low-latitude source of the low SSS water is found to be primarily Amazon River discharge west of 40°W and rainfall to the east. As the low-salinity water moves northward between 8° and 20°N during October–April, 70% of its freshwater in the upper 20 m is lost to the combination of evaporation, horizontal eddy diffusion, and vertical turbulent mixing, with an implied rate of SSS damping that is half of that for SST. During 1998–2012, interannual variations in SSS along 38°W are found to be negatively correlated with the strength of northward surface currents. The importance of ocean circulation for interannual variations of SSS and the small damping time scale for SSS emphasize the need to consider meridional freshwater advection when interpreting SSS variability in the tropical–subtropical North Atlantic.

Low noise 4-channel front end ASIC with on-chip DLL for the upgrade of the LHCb Calorimeter

An integrated circuit for the Upgrade of the LHCb Calorimeter front end electronics is presented. It includes four analog channels, a Delay Locked Loop (DLL) for signal phase synchronization for all channels and an SPI communication protocol based interface. The analog circuit is based on two fully differential interleaved channels with a switched integrator to avoid dead time and it incorporates dedicated solutions to achieve low noise, linearity and spill-over specifications. The included DLL is capable of shifting the phase of the LHC clock (25 ns) in steps of 1 ns. The selected technology is AMS SiGe BiCMOS 0.35 um.

Effect of the front surface field (a-Si:H) on the spectral response of thin films heterojunctions solar cells

The present paper accounts for a simulation study carried out to determine and optimize the effect of the high---low junction emitter front surface field (FSF) of thin heterojunction solar cell $$\text {n}^{+}$$n+(a-Si: H)/n(SiGe)/p(Si)). A theoretical model describing the behavior of heterojunction $$\text {n}^{+}$$n+---n---p type solar cells has been proposed. Besides, the expression of the photovoltaic equations allowing for the obtention of the optimal quantum efficiency of the solar cells based on the suggested model has been given. The effects of the a-Si:H-layer thickness and Ge fraction are discussed, using the computed results. The main role of an FSF layer is to reduce the effect of front surface recombination and the enhancement of light-generated free carriers' collection. This is primarily responsible for the increase of the spectral response compared with the conventional solar cell. This is achieved by the drastic reduction of the effective recombination at the emitter upper boundary and the optimum value of $$\text {n}^{+}$$n+ layer thicknesses (a-Si:H) is about 2 nm.

Impact characteristics of a vehicle population in low speed front to rear collisions

Rear impact collisions are mostly low severity, but carry a very high societal cost due to reported symptoms of whiplash and related soft tissue injuries. Given the difficulty in physiological measurement of damage in whiplash patients, there is a significant need to assess rear impact severity on the basis of vehicle damage. This paper presents fundamental impact equations on the basis of an equivalent single vehicle to rigid barrier collision in order to predict relationships between impact speed, maximum dynamic crush, mean and peak acceleration, time to common velocity and vehicle stiffness. These are then applied in regression analysis of published staged low speed rear impact tests. The equivalent mean and peak accelerations are linear functions of the collision closing speed, while the time to common velocity is independent of the collision closing speed. Furthermore, the time to common velocity can be used as a surrogate measure of the normalized vehicle stiffness, which provides opportunity for future accident reconstruction.

The differential influence of vowels and palatal covering on nasalance scores.

Objective : To investigate whether nasalance scores would differ when the hard palate and soft palate were covered during speech. Design : Nasalance scores were obtained during production of sentence stimuli loaded with differing vowel content across three conditions: (1) hard and soft palate uncovered (U); (2) hard palate covered by acrylic appliance (H); (3) both hard and soft palate covered by acrylic appliance (B). Sentences were loaded with high front, low front, high back, low back, or mixed vowels. Velopharyngeal closure was verified by nasoendoscopy. Participants : Six female adults with normal speech and resonance provided the speech samples. Main Outcome Measures : Nasalance scores for each of five sentences in each of three palatal conditions. Results : Mixed and high front sentences had significantly higher mean nasalance scores in the U (P < .01) and H (P < .05) conditions but not in the B condition. For all sentence stimuli combined across palatal conditions, there was a significant difference in mean nasalance scores between H and B conditions (P < .05) but not between the U condition and either the H or B conditions (P > .05). Conclusions : Data suggest that the primary place of transpalatal transfer of acoustic energy was the soft palate but only sentences with high-front vowels were affected by this phenomenon.

Low Cost and Power Software Defined Radio Using Raspberry Pi for Disaster Effected Regions

Radio communication is extremely critical for public safety, national safety, and emergency communication systems. During emergency situations like natural disasters, terrorist attacks and plane crashes, inter-operability problems are faced by military and civil safety officials where different aid agencies have radios working in different frequency bands, waveforms and protocols. At the same time, these radios need to be low cost, small size, portable, and require low power to operate. Software defined radio (SDR) technology helps to solve the above problems by implementing radios that can operate on multiple frequency bands and multiple protocols by software control. In this paper, we describe a novel SDR system that we have developed using Raspberry Pi, and a low cost front end solution. The system is low cost, small size, consumes low power and is portable, hence can be quickly deployed in disaster affected areas to save life and resources.

Análise Fitoquímica e Microbiológica da Atividade do Extrato Bruto Etanólico da Andiroba, Carapa guianensis Aubl.

Amazon in the population, in general, tends to use herbal medicines as medicinal plants for various diseases. Among the medicinal plants that are used is to Carapa guianensis Aubl. (crabwood), which has increasing application not only therapeutic, but also in chemical and cosmetic industries. The crude ethanol extract of the stem bark of Carapa guianensis Aubl. was determined using preliminary phytochemical study and antimicrobial activity. The phytochemical screening was performed by classical methods described by Matos (1997) cited by Rodrigues (2010). In the antimicrobial test was used Kirby-Bauer method modified cited Charles (2009) using the disk diffusion test with strains of Klebsiella pneumoniae (ATCC 13883), Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922), and antibiotics standardized, crude ethanol extract was used in concentrations 25mg/mL, 50mg/mL and 100mg/mL. Preliminary phytochemical analysis revealed the presence of phenols, tannins and anthraquinones. The crude ethanol extract of the bark of Carapa guianensis Aubl., showed low antimicrobial activity front strains of K. pneumoniae , and no activity against strains of S. aureus and E. coli . Key words: Carapa guianensis Aubl.; crabwood; antimicrobial.

Analysis of Equation for Convective Vorticity Vector during a Torrential Rainfall Process in Meiyu Season of 2011

Using NCEP FNL analysis data,black body temperature from FY-2E satellite,conventional and auto-metrological stations' observational precipitation data,and simulation output from high-resolution mesoscale model WRF V3. 3 to analyze a precipitation process in Jiang-Huai valley in June 2011. Analysis results show that the simulation results are in good agreement with the observations when comparing the precipitation betw een simulations and observations and reproduce the precipitation process well. This precipitation process was controlled and influenced by the surface low and Meiyu front systems. Period from 14 to 15 June is the mature phase of whole precipitation process,and the most significant character of this period is that many mesoscale convective systems move and develop along the Meiyu front. To investigate how MCS impacts on Meiyu front and torrential rainfall,convective vorticity vector and its vertical component tendency equation were employed to analyze. The result shows that local variation for the vertical component was influenced by the diabatic term,and the relationships among diabatic heating,secondary circulation and Meiyu frontogenesis imply a CISK-like response betw een MCS and Meiyu frontogenesis. So as a good atmospheric variable,the convective vorticity vector,especially,the vertical component can be used to diagnose and reveal the relationship betw een MCS associated with diabatic heating and Meiyu frontogenesis.

Frequency sensing of medical signals using low-voltage piezoelectric sensors

Piezoelectric sensors are used to pick up low level vibrations in automotive, biomedical and industrial fields and are subject to errors due to the input current and voltage noise of amplifiers, when connected with a large bias resistor. The noise levels, especially from the bias resistor, degrade the signal to noise ratio of the signal which leads to less reliable feature detection. We report the experimental investigation of a frequency sensing front-end in terms of its linearity, noise and gain in order to acquire medical signals at low frequencies and voltages, e.g. arterial pulse signal, Ballistocardiogram and heart sounds. An LC oscillator is used with a commercial phase locked loop for this purpose. We show that the noise levels in frequency sensing can be reduced by increasing the oscillation frequency, while maintaining 1% non-linearity. Overall, the readout runs at 5V and has a mean noise floor of 1.43μV/Hz and a non-linearity of 1% when subject to a sine wave between 20mV and 200mV peak to peak amplitude. The results of this work are expected to contribute towards low noise analog front end designs for piezoelectric sensors using frequency sensing as an alternate architecture.

The effect of plasma channel on the self-distortion of laser pulse propagating through the collisional plasma channel

In the present paper, laser pulse distortion/breakup and the effect of the plasma channel on the laser propagation through the collisional plasma have been studied by using moment theory approach. Second order nonlinear differential equations of the beam width parameter have been derived for the propagation of the laser through uniform homogenous plasma and preformed plasma channel having parabolic density profile. Differential equations of beam width parameter have been solved numerically using Runge Kutta method. It has been observed from analysis that when the laser pulse propagates through the homogenous plasma, the low intensity front and rear parts of the laser get defocused/diffracted and the high intensity central/main portion of the laser pulse gets self-guided. As a result of this, the laser pulse gets distorted. This distortion of the laser has not been observed when the laser pulse is propagated through the plasma channel having density minimum at the axis and maximum at the edges. The laser pulse is guided as a whole, even the low intensity front and rear parts of the laser are also guided. Therefore, the plasma channel is useful to prevent the distortion/breakup of the laser.

Relative distances among English front vowels produced by Korean and American speakers

This study examined the relative distances among English front vowels in a message produced by 47 Korean and American speakers from an internet speech archive in order to provide better pronunciation skills for Korean English learners. The Euclidean distances in the vowel space of F1 and F2 were measured among the front vowel pairs. The first vowel pair [i-ɛ] was set as the reference from which the relative distances of the other two vowel pairs were measured in percent in order to compare the vowel sounds among speakers of different vocal tract lengths. Results show that F1 values of the front vowels produced by the Korean and American speakers increased from the high front vowel to the low front vowel with differences among the groups. The Korean speakers generally produced the front vowels with smaller jaw openings than the American speakers did. Second, the relative distance of the high front vowel pair [i-ɪ] showed a significant difference between the Korean and American speakers while that of the low front vowel pair [ɛ-æ] showed a non-significant difference. Finally, the Korean speakers in the higher proficiency level produced the front vowels with higher F1 values than those in the lower proficiency level.

The effect of plasma channel on the self-distortion of laser pulse propagating through the collisionless plasma channel

This paper presents an investigation of the laser pulse distortion/breakup and the effect of the plasma channel on the laser propagation through the collisionless plasma. Moment theory has been used to derive differential equations of the beam width parameter of the laser propagating through uniform homogenous plasma and preformed plasma channel having parabolic density profile. Differential equations have been set up and solved numerically by using Runge Kutta method. From analysis, it is observed that the low intensity front and rear parts of the laser pulse get defocused/diffracted while the high intensity central portion of the laser pulse gets self-guided during the propagation through uniform homogenous plasma. As a result of this, laser pulse gets distorted. This distortion of the laser pulse has not been observed when the laser beam is propagated through the plasma channel having parabolic density profile. The laser pulse is guided as a whole, even the low intensity front and rear parts of the laser pulse are also guided. Therefore, it is predicted that plasma channel plays a significant role to prevent the distortion/beam breakup of the laser.

A frequency-sensing readout using piezoelectric sensors for sensing of physiological signals.

Together with a charge or voltage amplifier, piezoelectric sensors are commonly used to pick up physiological vibrations from the body. As an alternative to chopper or auto-zero amplifiers, frequency sensing is known in literature to provide advantages of noise immunity, interfacing to digital readout systems as well as tunable range of sensing. A frequency-sensing readout circuit for sensing low voltage signals from piezoelectric sensors is successfully developed and tested in this work. The output voltage of a piezoelectric sensor is fed to a varactor, which is part of an Colpitts LC oscillator. The oscillation frequency is converted into a voltage using a phase locked loop. The circuit is compared to a reference design in terms of linearity, noise and transfer function. The readout has a input-referred noise voltage of 2.24μV/√Hz and consumes 15 mA at 5V supply. Arterial pulse wave signals and the cardiac vibrations from the chest are measured from one subject to show the proof of concept of the proposed readout. The results of this work are intended to contribute towards alternative low noise analog front end designs for piezoelectric sensors.

Quantum efficiency investigations of type-II InAs/GaSb midwave infrared superlattice photodetectors

We present in this paper a comparison between different type-II InAs/GaSb superlattice (T2SL) photodiodes and focal plane array (FPA) in the mid-wavelength infrared domain to understand which phenomenon drives the performances of the T2SL structure in terms of quantum efficiency (QE). Our measurements on test photodiodes suggest low minority carrier diffusion length in the “InAs-rich” design, which penalizes carriers' collection in this structure for low bias voltage and front side illumination. This analysis is completed by a comparison of the experimental data with a fully analytic model, which allows to infer a hole diffusion length shorter than 100 nm. In addition, measurements on a FPA with backside illumination are finally presented. Results show an average QE in the 3–4.7 μm window equal to 42% for Ubias = −0.1 V, 77 K operating temperature and no anti-reflection coating. These measurements, completed by modulation transfer function and noise measurements, reveal that the InAs-rich design, despite a low hole diffusion length, is promising for high performance infrared imaging applications.