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A low power SAR ADC with fine-tuned time based adaptive sampling technique for ECG monitoring application in 180 nm CMOS

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INTEGRATION-THE VLSI JOURNAL 2025年 103卷

作者： Kandpal, Naveen Singh, Anil Agarwal, Alpana Thapar Inst Engn & Technol Elect & Commun Engn Patiala 147001 India

This work proposes an adaptive sampling SAR Analog-to-Digital converter (ADC) with a novel fine-tuned timebased sampling technique to dynamically adjust the sample rate for normal and abnormal ECG signals based on the characteristics of the incoming ECG signal. By integrating machine learning, the ADC adapts to varying signal conditions, ensuring accurate capture of essential data while maintaining energy efficiency, thereby enhancing the effectiveness of portable and wearable health monitoring devices. Unlike conventional methods, the Analog front end uses a time-based technique that effectively identifies and digitizes all critical information present in ECG signals. Additionally, the ADC incorporates a variable resolution scheme, enhancing power efficiency and reducing data bandwidth. The ADC adaptively allocates more bits to the most significant portions of the ECG waveform while reducing the resolution for less critical segments by employing a time-based approach. This enables efficient data representation and reduces overall data transfer requirements, making this architecture more power-efficient. Implemented in 180 nm CMOS technology, the proposed ADC consumes only 498.6 mu W with a 1.8 V supply and achieves ENOB of 5.21 bits, SNDR of 31.76 dB, and SFDR of 44.31 dB. The sampling frequency of the proposed architecture changes from 64 Hz to 512 Hz, which is suitable for portable ECG monitoring applications. The FoM of the proposed work ranges from 100 to 262 fj/conversion-step for 64-512 Hz sampling rate, respectively.

关键词： Adaptive sampling time-based sampling ECG monitoring Low power Machine learning

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A time-based sampling FRAMEWORK FOR FINITE-RATE-OF-INNOVATION SIGNALS

A TIME-BASED SAMPLING FRAMEWORK FOR FINITE-RATE-OF-INNOVATIO...

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IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Rudresh, Sunil Kamath, Abijith Jagannath Seelamantula, Chandra Sekhar Indian Inst Sci Dept Elect Engn Bangalore 560012 Karnataka India

ISBN: (纸本)9781509066315

time-based sampling of continuous-time signals is an alternative to Shannon's sampling paradigm in which the signal is encoded using a sequence of nonuniform time instants. The standard methods for reconstructing signals in bandlimited and shift-invariant spaces from their nonuniform measurements employ alternating projections algorithms. In this paper, we consider the problem of sampling and perfect reconstruction of periodic finite-rate-of-innovation (FRI) signals using crossing-time-encoding machine (C-TEM) and integrate-and-fire TEM (IF-TEM). We formulate the reconstruction problem in the frequency domain and develop techniques to compute the Fourier coefficients, which contain the unknown parameters of the signal in the form of a sum of weighted complex exponentials. The parameters are then estimated using high-resolution spectral estimation techniques. Unlike state-of-the-art methods, the proposed method is generalized to incorporate reconstruction of periodic FRI signals consisting of weighted and shifted versions of an arbitrary pulse with arbitrarily close delays, and is compatible with a large class of sampling kernels. We provide sufficient conditions for sampling and perfect reconstruction using C-TEM and IF-TEM. We present simulation results to support our claims. We also discuss an extension to the sampling of aperiodic FRI signals.

关键词： time-encoding machine (TEM) finite-rate-of-innovation signals time-based sampling crossing TEM integrate-and-fire TEM

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Robust time-based Finite-Rate-of-Innovation sampling Method and Hardware Implementation

Robust Time-Based Finite-Rate-of-Innovation Sampling Method ...

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IEEE International Instrumentation and Measurement Technology Conference (I2MTC) - Rising Above Covid-19

作者： Fu, Ning Zhang, Hongyi Qiao, Liyan Harbin Inst Technol Sch Elect & Informat Engn Harbin Peoples R China

ISBN: (纸本)9781665453837

Accurate measurement of parameters guarantees the quality of signal sampling. In the classical sampling framework, sampler measures the intensity of signal uniformly at specific times and operates at a sampling rate greater than Nyquist rate. An alternative sampling scheme, time encoding machine (TEM), can sample based on time measurements instead of measuring the intensity of signal. This paper research the problem of sampling finite-rate-of-innovation (FRI) signals using TEM. Compared with classical sampling, this sampling strategy can operate at a rate lower than Nyquist rate with low power consumption and less electromagnetic interference. We propose a robust reconstruction method by denoising samples in the frequency domain, which can improve the accuracy of reconstruction in the presence of noise. In addition, we present a TEM-based FRI sampling hardware system, which has not been seen in previous studies. And we compensate the non-ideal characteristics of device by system calibration. According to the experiments, the hardware system can sample and reconstruct the multi-pulse signal with certain numerical accuracy.

关键词： time-based sampling finite-rate-of-innovation time encoding machine sub-Nyquist sampling hardware system

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time-based Finite-Rate-of-Innovation sampling for Variable-Pulse-Width Signal

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IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 2024年 73卷 1页

作者： Fu, Ning Zhang, Hongyi Yun, Shuangxing Wei, Zhiliang Qiao, Liyan Harbin Inst Technol HIT Sch Elect & Informat Engn Harbin 150080 Peoples R China

The finite-rate-of-innovation (FRI) sampling method can reconstruct signals with few samples. However, classical FRI sampling often has serious model mismatch when dealing with asymmetric pulse signals. The variable-pulse-width (VPW) signal model is composed of asymmetric pulses with variable width, which can better match the asymmetric pulse signals in the actual signal measurement, such as electrocardiogram (ECG) and bidirectional reflectance distribution function (BRDF). The VPW-FRI sampling theory provides an effective alternative to sub-Nyquist sampling of such signals. Recent studies have used time encoding machine (TEM), an alternative sampling scheme, to replace the analog-to-digital converter in classical FRI frameworks. Such devices acquire signal samples through time measurement rather than measuring the intensity, with lower power consumption and less electronic interference. However, the existing TEM-FRI sampling methods do not match the VPW signal model. In this article, a sampling method based on TEM-FRI sampling scheme for VPW signals is proposed. We extend the signal model of TEM-FRI sampling framework to VPW signal, and give the mathematical derivation of the perfect reconstruction for VPW signal based on TEM-FRI sampling method. For the VPW signal containing K pulses, our method can guarantee the perfect reconstruction of VPW signals when the number of samples N >= 4K+1 in one signal period. And we present a robust reconstruction algorithm by denoising samples in the frequency domain, the simulation results show that our proposed method is more robust than classical FRI sampling method in the presence of noise. In addition, we present a TEM-based FRI sampling hardware system, and explain how to implement the sampling kernel in our hardware system with an analog filter device. According to the experiments, the TEM-FRI hardware system can sample and reconstruct the VPW signal.

关键词： Finite-rate-of-innovation (FRI) hardware system signal denoising sub-Nyquist sampling time-based sampling time encoding machine (TEM) variable pulse-width (VPW)

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FRI-TEM: time Encoding sampling of Finite-Rate-of-Innovation Signals

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2022年 70卷 2267-2279页

作者： Naaman, Hila Mulleti, Satish Eldar, Yonina C. Weizmann Inst Sci Fac Math & Comp Sci IL-76100 Rehovot Israel Indian Inst Technol Dept Elect Engn Mumbai 400076 Maharashtra India

Classical sampling is based on acquiring signal amplitudes at specific points in time, with the minimal sampling rate dictated by the degrees of freedom in the signal. The samplers in this framework are controlled by a global clock that operates at a rate greater than or equal to the minimal sampling rate. At high sampling rates, clocks are power-consuming and prone to electromagnetic interference. An integrate-and-fire time encoding machine (IF-TEM) is an alternative power-efficient sampling mechanism which does not require a global clock. Here, the samples are irregularly spaced threshold-based samples. In this paper, we investigate the problem of sampling FRI signals using an IF-TEM. We provide theoretical guarantees for a recently proposed recovery method to perfectly recover an FRI input. In addition, we propose a modified sampling approach in the presence of noise that is more robust than existing techniques. This method is also proven to ensure recovery in the noise-free setting. The modified approach requires twice the number of measurements compared to the existing method, however, it results in lower error in the presence of noise for the same number of measurements. Our results enable designing low-cost and energy-efficient analog-to-digital converters for FRI signals.

关键词： Kernel Encoding Clocks Power capacitors Channel coding Technological innovation Signal processing time-encoding machine (TEM) finite-rate-of-innovation (FRI) signals time-based sampling integrate and fire TEM (IF-TEM) sub-Nyquist sampling analog-to-digital conversion non-uniform sampling

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A time-to-first spike CMOS image sensor with coarse temporal sampling

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ANALOG INTEGRATED CIRCUITS AND SIGNAL PROCESSING 2006年第3期47卷 303-313页

作者： Luo, Q Harris, JG Chen, ZLJ Marvell Semicond Inc Sunnyvale CA USA

Conventional voltage-based CMOS image sensors inherently have a dynamic range of about 60 dB. To extend the dynamic range, a two-degree of freedom time-based CMOS image sensor is proposed. Instead of reading analog voltages off chip, a time representation is used to record when the photodetector voltage passes a timing-varying threshold. The time measurements are combined with the reference voltage waveform to reconstruct the image. Experimental results on a prototype 32 x 32 pixel array CMOS image sensor verify that the two-degree of freedom sampling technique is feasible for ultra-wide dynamic range imaging. A measured 115 dB dynamic range at 30 fps is obtained.

关键词： CMOS image sensor dynamic range time-based sampling

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UNIQUENESS AND ROBUSTNESS OF TEM-based FRI sampling

UNIQUENESS AND ROBUSTNESS OF TEM-BASED FRI SAMPLING

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IEEE International Symposium on Information Theory (ISIT)

作者： Naaman, Hila Mulleti, Satish Eldar, Yonina C. Weizmann Inst Sci Fac Math & Comp Sci Rehovot Israel Indian Inst Technol IIT Bombay Dept Elect Engn Bombay Maharashtra India

ISBN: (纸本)9781665421607;9781665421591

In this paper, we study the problem of sampling finite-rate-of-innovation (FRI) signals by using an integrate-and-fire time encoding machine. We consider a Fourier-domain reconstruction approach and design a robust sampling kernel that has a frequency-domain alias cancellation condition and excludes the zero frequency. In the absence of noise, we present theoretical recovery guarantees for FRI signals with arbitrary pulse shapes using our approach. We show that the minimum firing rate is proportional to the rate of innovation of the FRI signal. In the presence of noise, our technique results in 2-10 dB lower error while estimating the FRI parameters compared to existing methods for the same number of measurements.

关键词： time-encoding machine finite-rate-of-innovation signals time-based sampling integrate-and-fire

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Sample introduction in multi-syringe flow injection systems: comparison between time-based and volume-based strategies

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ANALYTICA CHIMICA ACTA 2005年第1-2期537卷 207-214页

作者： Segundo, MA Oliveira, HM Lima, JLFC Almeida, MIGS Rangel, AOSS Univ Porto Fac Farm Dept Quim Fis REQUIMTE P-4099030 Porto Portugal Univ Catolica Portuguesa Escola Super Biotecnol P-4200072 Porto Portugal

In multi-syringe flow injection analysis (MSFIA), devices as selection, injection or commutation valves must be incorporated to the manifold to provide access to sample and standard solutions. Therefore, the definition of sample amount can be either volume or time-based. In the present work, four configurations for sample introduction (two for each approach) were tested in order to establish if the different strategies affect the analytical signal in MSFIA systems. The mean absorbance value from ten consecutive injections of a bromothymol blue solution obtained for the time-based strategy was lower than that provided by the volume-based approach as the exact volume delivered by each configuration was different from the "theoretical" volume. For time-based configurations, the exact volume delivered is 2-5% lower than the theoretical value while for volume-based configurations, the volume delivered was between 6 and 46% larger than the theoretical volume. Moreover, for time-based sampling, the order of steps in the analytical cycle was of utmost importance since any alteration in the flow direction affected the volume delivered in the subsequent step in the analytical cycle. The influence of the two sampling approaches was also evaluated in the MSFIA systems for the spectrophotometric determination of phenolic compounds and the potentiometric determination of chloride. There was no evidence that the use of either volume or time-based sampling would improve the analytical features of these determinations when real samples were tested. (c) 2005 Elsevier B.V. All rights reserved.

关键词： multi-syringe flow injection sampling strategy time-based sampling volume-based sampling

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An examination of factors affecting propensities to use bicycle and pedestrian facilities in suburban locations

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TRANSPORTATION RESEARCH PART D-TRANSPORT AND ENVIRONMENT 2012年第4期17卷 341-348页

作者： Thakuriah, Piyushimita (Vonu) Metaxatos, Paul Lin, Jane Jensen, Elizabeth Univ Illinois Dept Urban Planning & Policy Chicago IL 60607 USA Univ Illinois Urban Transportat Ctr Chicago IL 60607 USA Univ Illinois Dept Civil & Mat Engn Chicago IL 60607 USA

The US federal Congestion Mitigation and Air Quality program was created to fund transportation projects that have the potential to contribute to the attainment or maintenance of the National Ambient Air Quality Standards. This study evaluates a random sample of eight suburban bicycle and pedestrian facilities funded by the Congestion Mitigation and Air Quality Program in the Chicago metro area. Users of these facilities were randomly sampled using a "time-based" user sampling approach and surveyed in intercept mode to implement a recall-based evaluation design. A random intercept logit model was used to explain variations in the propensity to switch from single occupant vehicle use to bicycling or walking, using attributes of users and sites. The analysis shows relatively low usage levels but that substitution of motorized modes have resulted, potentially leading to improved air quality outcomes. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Congestion Mitigation and Air Quality Non-motorized transportation facility Intercept survey time-based sampling Ex-post program evaluation

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EFFICIENT ECG RECONSTRUCTION AND HEART RATE MONITORING USING time-based SAMPLER

EFFICIENT ECG RECONSTRUCTION AND HEART RATE MONITORING USING...

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IEEE International Conference on Microwaves, Communications, Antennas, Biomedical Engineering and Electronic Systems (COMCAS)

作者： Naaman, Hila Bilik, Daniel Eder, Yonathan Eldar, Yonina C. Weizmann Inst Sci Fac Math & Comp Sci Rehovot Israel

ISBN: (纸本)9798350348194;9798350348187

Heart rate monitoring (HRM) based on electrocardiogram (ECG) is an important diagnostic technique for numerous cardiovascular conditions. To provide continuous, portable HRM, and rapid data transfer for instantaneous intervention, wireless technology is necessary, with limitations on system power, bandwidth, and resolution. Recent studies have demonstrated that ECG signals can be modeled as variable pulse width finite rate of innovation (VPW-FRI). In this paper, we develop a time-based VPW-FRI framework, using the power-efficient integrate-and-fire time encoding machine (IF-TEM) sampler. We introduce a method for time-based sub-Nyquist sampling and reconstruction of ECG signals, with application to HRM. Unlike standard sampling systems, the TEM-based sampler is asynchronous and does not require a power-consuming clock. Therefore, it can be exploited for medical applications, such as an energy-efficient pacemaker that may consume less space and power than conventional devices.

关键词： time-encoding machine ECG signal time-based sampling integrate-and-fire heart rate monitoring

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