scholarly journals Analysis and Reduction of Nonlinear Distortion in AC-Coupled CMOS Neural Amplifiers with Tunable Cutoff Frequencies

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3116
Author(s):  
Beata Trzpil-Jurgielewicz ◽  
Władysław Dąbrowski ◽  
Paweł Hottowy
Keyword(s):  
Large Scale ◽  
Nonlinear Distortion ◽  
Cutoff Frequency ◽  
Harmonic Distortion ◽  
Signal Frequency ◽  
Pass Filter ◽  
Silicon Area ◽  
Simple Modification ◽  
Coupling Circuit ◽  
The Impact

Integrated CMOS neural amplifiers are key elements of modern large-scale neuroelectronic interfaces. The neural amplifiers are routinely AC-coupled to electrodes to remove the DC voltage. The large resistances required for the AC coupling circuit are usually realized using MOSFETs that are nonlinear. Specifically, designs with tunable cutoff frequency of the input high‑pass filter may suffer from excessive nonlinearity, since the gate-source voltages of the transistors forming the pseudoresistors vary following the signal being amplified. Consequently, the nonlinear distortion in such circuits may be high for signal frequencies close to the cutoff frequency of the input filter. Here we propose a simple modification of the architecture of a tunable AC-coupled amplifier, in which the bias voltages Vgs of the transistors forming the pseudoresistor are kept constant independently of the signal levels, what results in significantly improved linearity. Based on numerical simulations of the proposed circuit designed in 180 nm technology we analyze the Total Harmonic Distortion levels as a function of signal frequency and amplitude. We also investigate the impact of basic amplifier parameters—gain, cutoff frequency of the AC coupling circuit, and silicon area—on the distortion and noise performance. The post-layout simulations of the complete test ASIC show that the distortion is very significantly reduced at frequencies near the cutoff frequency, when compared to the commonly used circuits. The THD values are below 1.17% for signal frequencies 1 Hz–10 kHz and signal amplitudes up to 10 mV peak-to-peak. The preamplifier area is only 0.0046 mm2 and the noise is 8.3 µVrms in the 1 Hz–10 kHz range. To our knowledge this is the first report on a CMOS neural amplifier with systematic characterization of THD across complete range of frequencies and amplitudes of neuronal signals recorded by extracellular electrodes.

scholarly journals An Area-Efficient and Highly Linear Reconfigurable Continuous-Time Filter for Biomedical Sensor Applications

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2065 ◽  
Author(s):  
Jinyong Zhang ◽  
Shing-Chow Chan ◽  
Hui Li ◽  
Nannan Zhang ◽  
Lei Wang
Keyword(s):  
Continuous Time ◽  
Frequency Tuning ◽  
Cutoff Frequency ◽  
Harmonic Distortion ◽  
Oxide Semiconductor ◽  
Cmos Process ◽  
Current Steering ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Silicon Area

This paper proposes a compact, high-linearity, and reconfigurable continuous-time filter with a wide frequency-tuning capability for biopotential conditioning. It uses an active filter topology and a new operational-transconductance-amplifier (OTA)-based current-steering (CS) integrator. Consequently, a large time constant τ , good linearity, and linear bandwidth tuning could be achieved in the presented filter with a small silicon area. The proposed filter has a reconfigurable structure that can be operated as a low-pass filter (LPF) or a notch filter (NF) for different purposes. Based on the novel topology, the filter can be readily implemented monolithically and a prototype circuit was fabricated in the 0.18 μm standard complementary-metal–oxide–semiconductor (CMOS) process. It occupied a small area of 0.068 mm2 and consumed 25 μW from a 1.8 V supply. Measurement results show that the cutoff frequency of the LPF could be linearly tuned from 0.05 Hz to 300 Hz and the total-harmonic-distortion (THD) was less than −76 dB for a 2 Hz, 200 mVpp sine input. The input-referred noises were 5.5 μVrms and 6.4 μVrms for the LPF and NF, respectively. A comparison with conventional designs reveals that the proposed design achieved the lowest harmonic distortion and smallest on-chip capacitor. Moreover, its ultra-low cutoff frequency and relatively linear frequency tuning capability make it an attractive solution as an analog front-end for biopotential acquisitions.

The Design of Gm-C Low-Pass Filter for Micromachined Gyroscope

2014 ◽  
Vol 609-610 ◽  
pp. 1072-1076
Author(s):  
Qiu Ye Lv ◽  
Chong He ◽  
Wen Jie Fan ◽  
Yu Feng Zhang ◽  
Xiao Wei Liu
Keyword(s):  
Process Model ◽  
Stop Band ◽  
Cutoff Frequency ◽  
Harmonic Distortion ◽  
Cmos Process ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
Simulation Results ◽  
Micromachined Gyroscope

In this Paper, a 4th-Order Low-Pass Gm-C Filter is Presented. for the Design of Operational Tranconductance Amplifier(OTA), it Adopts the Techniques of Current Division and Current Cancellation. these Techniques can Help to Achieve a Low Transconductance Value. for the Architecture of the 4th-Order Gm-C Filter, it Consists of Two Biquads. the Two Biquads are Cascade Connected. the Gm-C Low-Pass Filter has been Implemented under 0.5 μm CMOS Process Model. the Final Simulation Results Show the Cutoff Frequency of the Filter is 100Hz and the Stop-Band Attenuation is Larger than 60dB. the Power Consumption is Lower than 1mW and the Total Harmonic Distortion(THD) is -55dB.

scholarly journals A CMOS Programmable Fourth-Order Butterworth Active-RC Low-Pass Filter

Electronics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 204 ◽  
Author(s):  
Changchun Zhang ◽  
Long Shang ◽  
Yongkai Wang ◽  
Lu Tang
Keyword(s):  
Radio Frequency Identification ◽  
Supply Voltage ◽  
Cutoff Frequency ◽  
Cmos Technology ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Silicon Area ◽  
Fully Differential ◽  
Low Pass ◽  
Low Sensitivity

This paper presents a low-pass filter (LPF) for an ultra-high frequency (UHF) radio frequency identification (RFID) reader transmitter in standard SMIC 0.18 μm CMOS technology. The active-RC topology and Butterworth approximation function are employed mainly for high linearity and high flatness respectively. Two cascaded fully-differential Tow-Thomas biquads are chosen for low sensitivity to process errors and strong resistance to the imperfection of the involved two-stage fully-differential operational amplifiers. Besides, the LPF is programmable in order to adapt to the multiple data rate standards. Measurement results show that the LPF has the programmable bandwidths of 605/870/1020/1330/1530/2150 kHz, the optimum input 1dB compression point of −7.81 dBm, and the attenuation of 50 dB at 10 times cutoff frequency, with the overall power consumption of 12.6 mW from a single supply voltage of 1.8 V. The silicon area of the LPF core is 0.17 mm2.

Compact, Programmable, Two-Stage Configuration for Implantable Biopotential Recording Amplifiers

2019 ◽  
Vol 28 (14) ◽  
pp. 1920009 ◽  
Author(s):  
Mohammad Hossein Maghami ◽  
Amir Masoud Sodagar
Keyword(s):  
Feedback Loop ◽  
Supply Voltage ◽  
Cutoff Frequency ◽  
Harmonic Distortion ◽  
Two Stage ◽  
Silicon Area ◽  
Digitally Programmable ◽  
On Chip ◽  
Cmos Amplifier ◽  
Lower Cutoff

This paper proposes an area-efficient CMOS amplifier for neural recording applications. The proposed neural amplifier takes advantage of indirect negative feedback to realize a rather low upper [Formula: see text]3-dB cutoff frequency. As a result, the capacitance needed to realize the cutoff frequency is so small that can be easily implemented on-chip. Moreover, the proposed circuit also employs attenuators in the same feedback loop in order to further reduce the silicon area consumed by the capacitors and at the same time to increase the input impedance of the circuit. Designed based on a two-stage configuration, the amplifier provides tunable lower cutoff frequency and digitally-programmable upper cutoff frequency and voltage gain. The circuit is designed in a 0.18-[Formula: see text]m technology, and consumes 0.022[Formula: see text]mm2 and 0.27[Formula: see text]mm2 of chip areas for single- and eight-channel designs, respectively. Operated with a supply voltage of 1.8[Formula: see text]V, power consumption of the proposed amplifier is 36.7[Formula: see text][Formula: see text]W with the simulated input-referred noise of 4[Formula: see text][Formula: see text] over 1[Formula: see text]Hz–10[Formula: see text]kHz for each channel. The amplifier also provides an output swing of 0.95 Vpp with a total harmonic distortion of [Formula: see text]50[Formula: see text]dB at the frequency of 1[Formula: see text]kHz.

scholarly journals On Small Signal Frequency Stability under Virtual Inertia and the Role of PLLs

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2372 ◽  
Author(s):  
Sohail Khan ◽  
Benoit Bletterie ◽  
Adolfo Anta ◽  
Wolfgang Gawlik
Keyword(s):  
Frequency Measurement ◽  
Frequency Stability ◽  
Signal Frequency ◽  
Stable Operation ◽  
Small Signal ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
Virtual Inertia ◽  
The Impact

This paper presents a methodology that aims at identifying virtual inertia (VI) gain limitations from virtual synchronous generators (VSGs) while maintaining the frequency stability considering the delay associated with the frequency measurement process. The phase-locked loop (PLL) is typically used for frequency estimation that is used to calculate the rate of change of frequency (RoCoF) and it drives the VI loop. The PLL is generally accompanied by a low-pass filter that aims to suppress the impact of harmonics. This filter introduces a delay that when used with the VI control loop causes stability issues for high values of VI gain. A comparison of various PLL approaches suggests that certain variants tend to permit higher value of cut-off frequencies which can be utilized to increase the VI gain limit from VSG. This study presents a method by which the upper limit on VI gain can be quantified and related to the cut-off frequency of the PLL low pass filter that is indirectly representing the delay. It is performed using small signal frequency stability analysis on the frequency domain model of the grid with virtual inertia emulating VSG. The effective maximum VI gain from VSG is explored while satisfying the frequency measurement accuracy specification considering harmonics. The results show that the requirements of reaching a stable operation with sufficient stability margins can still be met with a faster PLL-based system and the potential increases in VI support from VSG can be quantified using the proposed method. The study has been first performed on a single machine single inverter bus (SMSIB) system and is generalized to the multi-machine and multi-inverter system.

scholarly journals Minimizing Harmonic Distortion Impact at Distribution System with Considering Large-Scale EV Load Behaviour Using Modified Lightning Search Algorithm and Pareto-Fuzzy Approach

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
S. N. Syed Nasir ◽  
J. J. Jamian ◽  
M. W. Mustafa
Keyword(s):  
Distribution System ◽  
High Performance ◽  
Large Scale ◽  
Search Algorithm ◽  
Distribution Network ◽  
Harmonic Distortion ◽  
Optimal Placement ◽  
Charging Station ◽  
Multiple Variable ◽  
The Impact

This research is focusing on optimal placement and sizing of multiple variable passive filter (VPF) to mitigate harmonic distortion due to charging station (CS) at 449 bus distribution network. There are 132 units of CS which are scheduled based on user behaviour within 24 hours, with the interval of 15 minutes. By considering the varying of CS patterns and harmonic impact, Modified Lightning Search Algorithm (MLSA) is used to find 22 units of VPF coordination, so that less harmonics will be injected from 415 V bus to the medium voltage network and power loss is also reduced. Power system harmonic flow, VPF, CS, battery, and the analysis will be modelled in MATLAB/m-file platform. High Performance Computing (HPC) is used to make simulation faster. Pareto-Fuzzy technique is used to obtain sizing of VPF from all nondominated solutions. From the result, the optimal placements and sizes of VPF are able to reduce the maximum THD for voltage and current and also the total apparent losses up to 39.14%, 52.5%, and 2.96%, respectively. Therefore, it can be concluded that the MLSA is suitable method to mitigate harmonic and it is beneficial in minimizing the impact of aggressive CS installation at distribution network.

Impact of COVID-19 on Nuclear Medicine in Germany, Austria and Switzerland: An International Survey in April 2020

2020 ◽  
Vol 59 (04) ◽  
pp. 294-299 ◽  
Author(s):  
Lutz S. Freudenberg ◽  
Ulf Dittmer ◽  
Ken Herrmann
Keyword(s):  
Nuclear Medicine ◽  
Health Systems ◽  
Personal Protective Equipment ◽  
Large Scale ◽  
Diagnostic Procedures ◽  
Protective Equipment ◽  
Current Crisis ◽  
Web Based ◽  
Public Versus Private ◽  
The Impact

Abstract Introduction Preparations of health systems to accommodate large number of severely ill COVID-19 patients in March/April 2020 has a significant impact on nuclear medicine departments. Materials and Methods A web-based questionnaire was designed to differentiate the impact of the pandemic on inpatient and outpatient nuclear medicine operations and on public versus private health systems, respectively. Questions were addressing the following issues: impact on nuclear medicine diagnostics and therapy, use of recommendations, personal protective equipment, and organizational adaptations. The survey was available for 6 days and closed on April 20, 2020. Results 113 complete responses were recorded. Nearly all participants (97 %) report a decline of nuclear medicine diagnostic procedures. The mean reduction in the last three weeks for PET/CT, scintigraphies of bone, myocardium, lung thyroid, sentinel lymph-node are –14.4 %, –47.2 %, –47.5 %, –40.7 %, –58.4 %, and –25.2 % respectively. Furthermore, 76 % of the participants report a reduction in therapies especially for benign thyroid disease (-41.8 %) and radiosynoviorthesis (–53.8 %) while tumor therapies remained mainly stable. 48 % of the participants report a shortage of personal protective equipment. Conclusions Nuclear medicine services are notably reduced 3 weeks after the SARS-CoV-2 pandemic reached Germany, Austria and Switzerland on a large scale. We must be aware that the current crisis will also have a significant economic impact on the healthcare system. As the survey cannot adapt to daily dynamic changes in priorities, it serves as a first snapshot requiring follow-up studies and comparisons with other countries and regions.

HOME VISITS DURING THE FIRST MONTH OF DELIVERY FOR RECENTLY DELIVERED WOMEN IN UTTAR PRADESH, INDIA

2020 ◽  
Vol 6 (5) ◽  
pp. 1183-1189
Author(s):  
Dr. Tridibesh Tripathy ◽  
Dr. Umakant Prusty ◽  
Dr. Chintamani Nayak ◽  
Dr. Rakesh Dwivedi ◽  
Dr. Mohini Gautam
Keyword(s):  
Large Scale ◽  
National Level ◽  
Uttar Pradesh ◽  
Life Time ◽  
Structured Interview ◽  
The Other ◽  
Registration System ◽  
Action Group ◽  
Current Article ◽  
The Impact

The current article of Uttar Pradesh (UP) is about the ASHAs who are the daughters-in-law of a family that resides in the same community that they serve as the grassroots health worker since 2005 when the NRHM was introduced in the Empowered Action Group (EAG) states. UP is one such Empowered Action Group (EAG) state. The current study explores the actual responses of Recently Delivered Women (RDW) on their visits during the first month of their recent delivery. From the catchment area of each of the 250 ASHAs, two RDWs were selected who had a child in the age group of 3 to 6 months during the survey. The response profiles of the RDWs on the post- delivery first month visits are dwelled upon to evolve a picture representing the entire state of UP. The relevance of the study assumes significance as detailed data on the modalities of postnatal visits are available but not exclusively for the first month period of their recent delivery. The details of the post-delivery first month period related visits are not available even in large scale surveys like National Family Health Survey 4 done in 2015-16. The current study gives an insight in to these visits with a five-point approach i.e. type of personnel doing the visit, frequency of the visits, visits done in a particular week from among those four weeks separately for the three visits separately. The current study is basically regarding the summary of this Penta approach for the post- delivery one-month period.     The first month period after each delivery deals with 70% of the time of the postnatal period & the entire neonatal period. Therefore, it does impact the Maternal Mortality Rate & Ratio (MMR) & the Neonatal Mortality Rates (NMR) in India and especially in UP through the unsafe Maternal & Neonatal practices in the first month period after delivery. The current MM Rate of UP is 20.1 & MM Ratio is 216 whereas the MM ratio is 122 in India (SRS, 2019). The Sample Registration System (SRS) report also mentions that the Life Time Risk (LTR) of a woman in pregnancy is 0.7% which is the highest in the nation (SRS, 2019). This means it is very risky to give birth in UP in comparison to other regions in the country (SRS, 2019). This risk is at the peak in the first month period after each delivery. Similarly, the current NMR in India is 23 per 1000 livebirths (UNIGME,2018). As NMR data is not available separately for states, the national level data also hold good for the states and that’s how for the state of UP as well. These mortalities are the impact indicators and such indicators can be reduced through long drawn processes that includes effective and timely visits to RDWs especially in the first month period after delivery. This would help in making their post-natal & neonatal stage safe. This is the area of post-delivery first month visit profile detailing that the current article helps in popping out in relation to the recent delivery of the respondents.   A total of four districts of Uttar Pradesh were selected purposively for the study and the data collection was conducted in the villages of the respective districts with the help of a pre-tested structured interview schedule with both close-ended and open-ended questions.  The current article deals with five close ended questions with options, two for the type of personnel & frequency while the other three are for each of the three visits in the first month after the recent delivery of respondents. In addition, in-depth interviews were also conducted amongst the RDWs and a total 500 respondents had participated in the study.   Among the districts related to this article, the results showed that ASHA was the type of personnel who did the majority of visits in all the four districts. On the other hand, 25-40% of RDWs in all the 4 districts replied that they did not receive any visit within the first month of their recent delivery. Regarding frequency, most of the RDWs in all the 4 districts received 1-2 times visits by ASHAs.   Regarding the first visit, it was found that the ASHAs of Barabanki and Gonda visited less percentage of RDWs in the first week after delivery. Similarly, the second visit revealed that about 1.2% RDWs in Banda district could not recall about the visit. Further on the second visit, the RDWs responded that most of them in 3 districts except Gonda district did receive the second postnatal visit in 7-15 days after their recent delivery. Less than half of RDWs in Barabanki district & just more than half of RDWs in Gonda district received the third visit in 15-21 days period after delivery. For the same period, the majority of RDWs in the rest two districts responded that they had been entertained through a home visit.

The Impact of Quantitative Easing on Emerging Markets – Literature Review

e-Finanse ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 67-76
Author(s):  
Piotr Bartkiewicz
Keyword(s):  
Emerging Markets ◽  
Large Scale ◽  
Empirical Literature ◽  
Quantitative Easing ◽  
Methodological Choices ◽  
The Subject ◽  
Methodological Approaches ◽  
The Impact ◽  
Sufficient Precision

AbstractThe article presents the results of the review of the empirical literature regarding the impact of quantitative easing (QE) on emerging markets (EMs). The subject is of interest to policymakers and researchers due to the increasingly larger role of EMs in the world economy and the large-scale capital flows occurring after 2009. The review is conducted in a systematic manner and takes into consideration different methodological choices, samples and measurement issues. The paper puts the summarized results in the context of transmission channels identified in the literature. There are few distinct methodological approaches present in the literature. While there is a consensus regarding the direction of the impact of QE on EMs, its size and durability have not yet been assessed with sufficient precision. In addition, there are clear gaps in the empirical findings, not least related to relative underrepresentation of the CEE region (in particular, Poland).

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