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Biomedical Circuits and Systems Conference, 2007. BIOCAS 2007. IEEE

Date 27-30 Nov. 2007

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Displaying Results 1 - 25 of 73
  • A New Brain Imaging Device Based on fNIRS

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB) |  | HTML iconHTML  

    A new portable brain imaging device based on continuous-wave functional near-infrared spectrometry (fNIRS) is presented. The source-detector part is composed of a multi-wavelength LED and a silicon photodetector that are directly placed on the scalp of the subject. The dimensions of the proposed device are small, as it has to be mounted on the head of an adult person. Acquired data are transmitted in real-time to a laptop for post processing using Matlab. Time- multiplexed light is used to achieve a higher SNR while keeping the device safe for long-term wearing. Preliminary evaluation on adults gave the expected accuracy and compare well with fNIRS characteristics found in literature, that are collected from bulky equipment. With a noise figure of -47 dB and a sampling rate of 23 Hz, the presented device is appropriate to isolate hemodynamic variations, which are strongly related to local cerebral activity. View full abstract»

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  • A Differential Pressure Approach to Spirometry

    Page(s): 5 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (686 KB) |  | HTML iconHTML  

    This paper presents the design, implementation and measurements of a spirometer based on differential pressure sensing. A system which fulfills the last medical standard specifications has been designed exploiting the Venturi tube principle. A fully operating prototype has been tested, and data have been subsequently analyzed. Air flows up to 14 L/s can be measured with an accuracy of 0.2 L/s. Data acquisition software and user interface were developed. View full abstract»

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  • A Wearable Inertial Sensing Technology for Clinical Assessment of Tremor

    Page(s): 9 - 12
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB) |  | HTML iconHTML  

    TEMPO (Technology-Enabled Medical Precision Observation) 1.0 is a novel, first-generation, wearable data collection and analysis platform for assessment of a variety of human movement disorders, including tremor. It enables quantitative, objective, and continuous measurement of movement with minimal invasiveness and inconvenience to the patient and clinician, respectively. This system meets requirements for wearability, data storage, sampling rate, number of sensors, interface methods, and form factor, which are necessary for applications on person. In addition to the design and development of a basic data acquisition device, various circuits and systems were engineered to interface wearable, triaxial MEMS inertial sensors. Furthermore, custom data analysis software that processes datasets collected from the device and sensors, was created, and has demonstrated clinical utility in the analysis of tremor. Data processing techniques include a unique filtering scheme and a novel application of cross-correlation. The analysis was conducted pre- and post-operatively, in conjunction with the University of Virginia's Department of Neurosurgery, for a study of deep brain stimulation efficacy. This paper presents the engineering of and experimental results obtained with TEMPO 1.0 technology in the clinical assessment of tremor. View full abstract»

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  • Wireless Data Links for Biomedical Implants: Current Research and Future Directions

    Page(s): 13 - 16
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (414 KB) |  | HTML iconHTML  

    This paper outlines the requirements for high-rate implantable data links as would be used in applications such as visual prostheses. Methods used in current research are categorized and recently reported implementations are discussed and compared. The most significant shortcoming of current implementations is in their data rates which are limited to several Mb/s, while rates of several tens of Mb/s are envisioned to be necessary for a functional visual prosthesis. Several promising methods for achieving increased data rates are discussed, including ultra-wide band signaling, infrared transmission, and body conduction techniques. View full abstract»

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  • Efficient Computation of the LF/HF Ratio in Heart Rate Variability Analysis Based on Bitstream Filtering

    Page(s): 17 - 20
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (606 KB) |  | HTML iconHTML  

    This paper describes a novel approach to hardware efficient computing of the LF/HF ratio as required in heart rate variability (HRV) analysis. Heart rate data are converted into a bit stream vie delta-sigma modulation. The bit stream is filtered in the LF and HF sub-bands using novel hardware architecture. Sub-band spectral content is estimated from the filtered signals. The proposed algorithm and hardware architecture is extremely efficient, making continuous real-time HRV analysis possible in low-power microelectronics. View full abstract»

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  • Fully Integrated Impedance Spectroscopy Systems for Biochemical Sensor Array

    Page(s): 21 - 24
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (683 KB) |  | HTML iconHTML  

    With rapid progress in the miniaturization of biosensors, array microsystems utilizing impedance spectroscopy (IS) are of emerging interest. Focused on the electronics portion of such IS microsystems, this paper analyzes FFT-based and frequency response analyzer (FRA)-based approaches and compares them for hardware efficiency in array applications. For the chosen FRA-based approach, two possible systems are described and their circuit-level realizations are presented, one targeting high accuracy applications and the other prioritizing rapid interrogation. View full abstract»

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  • Long-term monitoring of electrochemical parameters from stimulated neural tissues

    Page(s): 25 - 28
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1055 KB) |  | HTML iconHTML  

    The electrode-tissues interface (ETI) is one of the key issues for the safety, reliability and efficiency of implantable devices such as stimulators and sensors. The aim of this paper is to report an implantable telemetry device, based on a full custom integrated circuit (IC) to monitor the ETI. The proposed system performs various types of measurements, such as impedance spectroscopy, cyclic voltammetry, and galvanostatic double pulse method. Hence, the evolution of various electrochemical parameters of the ETI such as complex impedance, faradic resistance, double layer capacity, rheobase current, and chronaxy time, could be monitored long time after implantation. The full custom IC has been designed and fabricated with the CMOS 0.18 mum technology. The circuit occupies a silicon area of 2 mm2, and consumes less than 3 mW. Characterisation and in-vitro experimental results validate the full functionalities of the implantable monitoring system including the custom IC. View full abstract»

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  • A Molecular bio-wire based multi-array biosensor with integrated potentiostat

    Page(s): 29 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (517 KB) |  | HTML iconHTML  

    One of the important factors determining the sensitivity of any biosensing system is successful integration of bio- molecular transducers with peripheral signal processing circuitry. In this paper we present an architecture of a multi-array biosensor that integrates molecular bio-wires based immunosensor with a multi-channel potentiostat array. The biosensor operates by converting binding events between antigen and antibody into a measurable electrical signal using polyaniline nanowires as a transducer. The electrical signal is measured using a multichannel potentiostat where each channel comprises of a semi- synchronous SigmaDelta modulator. Measured results using a fabricated potentiostat array demonstrate sensitivity down to 50 femtoampere range which makes it ideal for detecting pathogens at low concentration levels. Experiments using the biosensor array specific to Bacillus Cereus bacterium validate the functionality of the platform in detecting the pathogen at different concentration levels. View full abstract»

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  • Electrical Noise Analysis of an Integrated Patch-Clamp Amplifier

    Page(s): 33 - 36
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1226 KB) |  | HTML iconHTML  

    This paper presents an evaluation of electrical noise sources and signal-to-noise limitations in a fabricated integrated patch-clamp amplifier. We also present numerical calculation of the theoretical noise of the patch-clamp system. Our fabricated device was measured to have less than 4pA of rms noise at 10 kHz bandwidth, similar in performance to commercial bench- top systems. The integrated patch-clamp can accurately measure nano-Amperes of current and is intended for a high-throughput system that can screen a large number of cells in parallel. The fabricated device consumes 1480 by 1300 mum of silicon area and 3.2 mW at 3.3 V of power. The device was fabricated using AMI 0.5 mA Micron technology. View full abstract»

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  • A Passive Telemetry Interface System with Closed-loop Power Control Function for Body-implanted Applications

    Page(s): 37 - 40
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (894 KB) |  | HTML iconHTML  

    In this paper, we propose a passive telemetry interface system for a body-implanted chip with a closed-loop power control function, which keeps the chip temperature at the allowable level for human body. The system is controlled by monitoring an excessive current at the implanted chip and limiting the power supply at the external interrogator unit. Power consumption of the current monitor circuit implemented in 0.18 mum standard CMOS technology is lower than 35 muW with a 1.8 V power supply. Experimental results of the closed-loop power control system confirm its expected features of a detecting current of 150 muA at a distance between the transponder and the interrogator less than 10 mm. View full abstract»

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  • Feasibility Study of Printed Capsule Antennas for Medication Compliance Monitoring

    Page(s): 41 - 44
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1161 KB) |  | HTML iconHTML  

    This paper presents a feasibility study of printed capsule antennas for medication compliance monitoring. During clinical trials, it is important to know with certainty a patient's compliance to a medication regimen, because without it, the results cannot be interpreted accurately. Small antennas printed directly onto the surface of standard capsule can potentially serve as a cost-effective method of validating medication compliance via electronic detection of a swallowed pill in the digestive tract. In this paper, we investigate various aspects of these "electronics pills," including printing methods, conductive inks and radiation characteristics of electrically small antennas inside the human body. We employ realistic antenna models and electromagnetic simulations based on the finite difference time domain method to determine the radiated field intensities for sources in the body. Phantoms solutions with electrical properties that are approximately equivalent to biological tissue are used to experimentally validate simulated results and characterize signal attenuation of electrically small radiation sources in the human torso. View full abstract»

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  • A Bidirectional Wireless Link for Neural Prostheses that Minimizes Implanted Power Consumption

    Page(s): 45 - 48
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1011 KB) |  | HTML iconHTML  

    We describe a bidirectional impedance-modulation wireless data link for implanted neural prostheses. The link uses near-field inductive coupling between the implanted system and an external transceiver. It is designed to minimize power consumption in the implanted system and support high data rates in the uplink direction (from the implanted to the external system). Experimental results demonstrate data transfer rates up to 5.8 Mbps in the uplink direction and 300 kbps in the downlink direction at a link distance of 2 cm. The link dissipates 100 muW in the implanted system and 2.5 mW in the external system, making it among the most power-efficient inductive data links reported. View full abstract»

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  • A Mixed-Signal Multi-Chip Neural Recording Interface with Bandwidth Reduction

    Page(s): 49 - 52
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2428 KB) |  | HTML iconHTML  

    We present the design of a multi-chip neural interface intended for multi-channel neural recording. The design features a mixed-signal part that handles neural signal conditioning, digitization and time-division multiplexing, and a digital part that provides control, bandwidth reduction, and serial communications towards a host interface. The two CMOS 0.18-mum fabricated embedded circuits that implement both parts are directly mounted on the back of a medical-grade stainless steel microelectrodes array and wire-bonded to its post-processed base. The presented neural interface integrates 16 channels for validation; however, the proposed approach is scalable to larger channel counts. In fact, it is suitable to implement microsystems including several hundreds of recording channels. The performance of the implemented multi-channel interface was validated with real neural waveforms. View full abstract»

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  • Optimization criteria in the design of medical UWB radars in compliance with the regulatory masks

    Page(s): 53 - 58
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1079 KB) |  | HTML iconHTML  

    A general method is described to select an optimal set of parameters to design a pulse radar system [1] for heart motion detection [2,3]- Relating to the tracking of heart wall movement, the required acquisition time and sampling frequency are determined and subsequently pulse repetition frequency, pulse echo averaging and pulse power are obtained under regulatory mask power limitations defined for UWB emissions [4,5]. Although essentially theoretical and sometimes quite trivial, the reported model may be used as a reference for the parameters setting in the design of UWB radars for the acquisition of the temporal motion signal of internal body organs [6,7]. View full abstract»

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  • On the Swept-threshold Sampling in UWB Medical Radar

    Page(s): 59 - 62
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (287 KB) |  | HTML iconHTML  

    The non-invasive techniques to measure vital signs have received much attention lately. They exhibit several advantages compared to the traditional invasive techniques. One such technique can be based on radar principles. In this paper we scrutinize the statistical properties of a medical radar developed on a single CMOS chip, which operates in the ultra wideband from 3.1 GHz to 10.6 GHz. A key part of the chip is based on a new technique for sampling at very high frequencies called swept- threshold sampling. This is based on multiple pulse emissions, accumulation and range-gating. We derive expressions for the bias and variance of swept-threshold sampling and show that the bias is a strong function of noise power and input value, but independent of the swept-threshold parameters for a fixed input range. The variance is shown to be proportional to the quantization step size and standard deviation of the noise process. Finally, simulation results are provided as proof of concept, and they show that the derived theoretical equations for bias and mean square error are valid. View full abstract»

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  • An Ultra-low-Power Quadrature PLL in 130nm CMOS for Impulse Radio Receivers

    Page(s): 63 - 66
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1411 KB) |  | HTML iconHTML  

    This paper discusses an architecture for an integrated ultra-low power impulse radio receiver for low data rate applications such as biomedical sensor networks. Choosing a proper system architecture allows to implement a receiver with relaxed specifications for the typical building blocks which results in a low-power implementation. Furthermore a design in 130 nm CMOS of a fully integrated ultra-low power PLL, a critical block of such receivers, is presented. The PLL serves a double purpose. It acts as the master clock generator for the receiver and it is also used to generate a template waveform for pulse reception. The latter requires the PLL to have quadrature outputs since the receiver uses I/Q reception. Because rather relaxed specifications in terms of phase-noise are required, a differential ring VCO with an even amount of stages is a suitable topology. The VCO has a measured center frequency of 568 MHz and a tuning range of 23%. It achieves a phase-noise of -91 dBc/Hz @ 1 MHz offset. The PLL employs a divide-by-8 and locks to an externally applied 75 MHz clock. Measurements show a total power consumption less than 200 muW with an rms jitter of 24 ps on an output clock of 600 MHz. View full abstract»

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  • Impulse Radio technology for Biomedical applications

    Page(s): 67 - 70
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (313 KB) |  | HTML iconHTML  

    Improving quality of service in wireless communication links is of vital importance in biomedical applications. Current wireless technology is far from satisfactory conveying vital signs in personalized healthcare. Nevertheless current technology like Bluetooth and ZigBee is explored even for critical monitoring of patients, both in hospital environments and homecare. In this paper we are exploring impulse radio as a feasible technology for health monitoring. By exploring advanced technology and novel architectures, improved quality of service may be granted. Additional interesting biomedical functionality of impulse radio is detached body sensors (short-range medical radar). View full abstract»

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  • Reliable Computation in Noisy Backgrounds Using Real-Time Neuromorphic Hardware

    Page(s): 71 - 74
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1041 KB) |  | HTML iconHTML  

    Spike-time based coding of neural information, in contrast to rate coding, requires that neurons reliably and precisely fire spikes in response to repeated identical inputs, despite a high degree of noise from stochastic synaptic firing and extraneous background inputs. We investigated the degree of reliability and precision achievable in various noisy background conditions using real-time neuromorphic VLSI hardware which models integrate-and-fire spiking neurons and dynamic synapses. To do so, we varied two properties of the inputs to a single neuron, synaptic weight and synchrony magnitude (number of synchronously firing pre-synaptic neurons). Thanks to the realtime response properties of the VLSI system we could carry out extensive exploration of the parameter space, and measure the neurons firing rate and reliability in real-time. Reliability of output spiking was primarily influenced by the amount of synchronicity of synaptic input, rather than the synaptic weight of those synapses. These results highlight possible regimes in which real-time neuromorphic systems might be better able to reliably compute with spikes despite noisy input. View full abstract»

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  • FPGA Based Silicon Spiking Neural Array

    Page(s): 75 - 78
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2496 KB) |  | HTML iconHTML  

    Rapid design time, low cost, flexibility, digital precision, and stability are characteristics that favor FPGAs as a promising alternative to analog VLSI based approaches for designing neuromorphic systems. High computational power as well as low size, weight, and power (SWAP) are advantages that FPGAs demonstrate over software based neuromorphic systems. We present an FPGA based array of Leaky-Integrate and Fire (LIF) artificial neurons. Using this array, we demonstrate three neural computational experiments: auditory Spatio-Temporal Receptive Fields (STRFs), a neural parameter optimizing algorithm, and an implementation of the Spike Time Dependant Plasticity (STDP) learning rule. View full abstract»

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  • Spike-Based MAX Networks for Nonlinear Pooling in Hierarchical Vision Processing

    Page(s): 79 - 82
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (677 KB) |  | HTML iconHTML  

    Complex cells in the visual cortex utilize a maximum (MAX) operation to pool the outputs of simple cells to achieve feature specificity and invariance. We demonstrate a biologically-plausible MAX network for nonlinear pooling in hardware, using a reconfigurable multichip address event representation based VLSI system. With this implementation we have shown that we can implement simple and advanced stages of visual processing on the same chip and are one step closer to constructing an autonomous, continuous-time, biologically- plausible hierarchical model of visual information processing using large-scale arrays of identical silicon neurons. View full abstract»

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  • A Scalable Architecture for Event-Based Cross-Correlation

    Page(s): 83 - 86
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2305 KB) |  | HTML iconHTML  

    We present an architecture for a bio-inspired circuit that implements a wide-range cross-correlation. The circuit implements a stochastic approximation to mathematical cross-correlation. The basic circuit element is a noise-driven oscillator consisting of an integrator, a Schmitt inverter, and a switch which switches between the two signals to be cross-correlated. These elements can be developed into an NxN array which extends the cross-correlation range and improves the speed and accuracy of the approximation. View full abstract»

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  • Robust classification of correlated patterns with a neuromorphic VLSI network of spiking neurons

    Page(s): 87 - 90
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3850 KB) |  | HTML iconHTML  

    We demonstrate robust classification of correlated patterns of mean firing rates, using a VLSI network of spiking neurons and spike-driven plastic synapses. The synapses have bistable weights over long time-scales and the transitions from one stable state to the other are driven by the pre and postsynaptic spiking activity. Learning is supervised by a teacher signal which provides an extra current to the output neurons during the training phase. This current steers the activity of the neurons toward the desired value, and the synaptic weights are modified only if the current generated by the plastic synapses does not match the one provided by the teacher signal. If the neuron's response matches the desired output, the synaptic updates are blocked. Such a feature allows the neurons to classify spatial patterns of mean firing rates, even when they have significant correlations. If synaptic updates are stochastic, as in the case of random Poisson input spike trains, the classification performance can be further improved by combining the outcome of multiple neurons together. View full abstract»

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  • A 2-D Cochlea with Hopf Oscillators

    Page(s): 91 - 94
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (658 KB) |  | HTML iconHTML  

    In this paper we present the circuits for a 2-D silicon cochlea whose basilar membrane resonant elements are constructed using oscillators whose dynamic behaviour is governed by the Hopf differential equation. By using Hopf oscillators we are able to model some of the behaviour of the outer hair cells (OHCs) whose action is responsible for the cochlea's nonlinear behaviour. View full abstract»

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  • Ultra-low Spike Rate Silicon Neuron

    Page(s): 95 - 98
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (331 KB) |  | HTML iconHTML  

    We present theory, design and simulation results for a silicon neuron circuit that achieves extremely low spike rates and small footprint by exploiting the low current characteristics in floating gate structures. As in biological counterparts, the spike rate is compressed against stimulant current. Simulations confirm sub-Hertz spike rates in steady state with a stimulant current of 7pA and below, and up to 100x spike rate reduction at InA. With reasonable device variation modelling, Monte Carlo simulation shows that spike rate varies by a standard deviation of 25%. View full abstract»

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  • Stochastic Synapse with Short-Term Depression for Silicon Neurons

    Page(s): 99 - 102
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (287 KB) |  | HTML iconHTML  

    We report a stochastic dynamical synapse for VLSI spiking neural systems. The compactness of the circuit, real-time stochastic behavior, and probability tuning make it well suitable to implement stochastic synapses with variety of dynamics. The stochastic synapse implements short-term depression (STD) using a subtractive single release model. Preliminary experimental results show a good match with theoretical predictions. The output from the stochastic synapse with STD has negative autocorrelation and lower power spectral density at low frequencies which can remove the information redundancy in the input spike train. The mean transmission probability is inversely proportional to the input spike rate which has been suggested as an automatic gain control mechanism in neural systems. The silicon stochastic synapse with plasticity could potentially be a powerful addition to existing deterministic VLSI spiking neural systems. View full abstract»

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