By Topic

Circuits and Systems I: Regular Papers, IEEE Transactions on

Issue 12 • Date Dec. 2005

Filter Results

Displaying Results 1 - 25 of 38
  • Table of contents

    Page(s): c1 - c4
    Save to Project icon | Request Permissions | PDF file iconPDF (103 KB)  
    Freely Available from IEEE
  • IEEE Transactions on Circuits and Systems—I: Regular Papers publication information

    Page(s): c2
    Save to Project icon | Request Permissions | PDF file iconPDF (36 KB)  
    Freely Available from IEEE
  • From the Desk of the Editor-in-Chief

    Page(s): 2509 - 2510
    Save to Project icon | Request Permissions | PDF file iconPDF (176 KB)  
    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Guest Editorial

    Page(s): 2511 - 2514
    Save to Project icon | Request Permissions | PDF file iconPDF (336 KB)  
    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultra-wide-band transmitter for low-power wireless body area networks: design and evaluation

    Page(s): 2515 - 2525
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1544 KB)  

    The successful realization of a wireless body area network (WBAN) requires innovative solutions to meet the energy consumption budget of the autonomous sensor nodes. The radio interface is a major challenge, since its power consumption must be reduced below 100 μW (energy scavenging limit). The emerging ultra-wide-band (UWB) technology shows strong advantages in reaching this target. First, most of the complexity of an UWB system is in the receiver, which is a perfect scenario in the WBAN context. Second, the very little hardware complexity of a UWB transmitter offers the potential for low-cost and highly integrated solutions. Finally, in a pulse-based UWB scheme, the transmitter can be duty-cycled at the pulse rate, thereby reducing the baseline power consumption. We present a low-power UWB transmitter that can be fully integrated in standard CMOS technology. Measured performances of a fully integrated pulse generator are provided, showing the potential of UWB for low power and low cost implementations. Finally, using a WBAN channel model, we present a comparison between our UWB solution and state-of-the-art low-power narrow-band implementations. This paper shows that UWB performs better in the short range due to a reduced baseline power consumption. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An implantable wireless bidirectional communication microstimulator for neuromuscular stimulation

    Page(s): 2526 - 2538
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1256 KB) |  | HTML iconHTML  

    This paper presents the integrated circuit design for a wireless bidirectional transmission microstimulator. This implantable device is composed of an internal radio-frequency (RF) front-end circuit, a control circuit, a stimulator, and an on-chip transmitter. A 2-MHz amplitude-shift keying modulated signal, including the power and data necessary for the implantable device, is received, and a stable 3-V dc voltage and digital data will be extracted to further execute neuromuscular stimulation. The current-mode microstimulator can produce a bidirectional output current with 8-bit resolution for stimulation. The maximum stimulation current is 1 mA while the stimulation frequency is from 20 Hz to 2 kHz and the pulsewidth of stimulation current is from 150 to 500 μs. Furthermore, the system can acquire the biological sensing signal by means of an on-chip transmitter. Most of the signal processing circuits have been designed with low-power schemes to reduce the power consumption, and the performance is also conformed to the requirements of the microstimulator. All of the circuits except for the RF link are combined in a single chip and implemented in TSMC 0.35-μm 2P4M standard CMOS process. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Low-power CMOS wireless MEMS motion sensor for physiological activity monitoring

    Page(s): 2539 - 2551
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1544 KB)  

    In this paper, a short distance wireless sensor node "AccuMicroMotion" for physiological activity monitoring is proposed for detecting motions in six degrees of freedom. System architecture, relevant microstructures, and electronic circuits to implement the sensor node are presented. A three-axis microelectromechanical systems (MEMS) accelerometer and a z-axis gyroscope are designed and fabricated using a new deep-reactive ion-etch CMOS-MEMS process. The interface circuits, an analog-to-digital converter, and a wireless transmitter are designed using Taiwan Semiconductor Manufacturing Company 0.35-μm CMOS process, wherein the interface circuits adopt chopper stabilization technique and can resolve a signal (dc to 1 kHz) as low as 200 nV from the microsensors; digitized outputs from the microsensors are transmitted by a 900-MHz amplitude-shift-keying radio-frequency transmitter that delivers a 2.2-mW power to a 50-Ω antenna. The system draws an average current of 4.8 mA from a 3-V supply when six sensors are in operation simultaneously and provides an overall 60-dB dynamic range. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A fully integrated low-power BPSK demodulator for implantable medical devices

    Page(s): 2552 - 2562
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB) |  | HTML iconHTML  

    During the past decades, research has progressed on the biomedical implantable electronic devices that require power and data communication through wireless inductive links. In this paper, we present a fully integrated binary phase-shift keying (BPSK) demodulator, which is based on a hard-limited COSTAS loop topology, dedicated to such implantable medical devices. The experimental results of the proposed demodulator show a data transmission rate of 1.12 Mbps, less than 0.7 mW consumption under a supply voltage of 1.8 V, and silicon area of 0.2 mm2 in the Taiwan Semiconductor Manufacturing Company (TSMC) CMOS 0.18-μm technology. The transmitter satisfies the requirement of applications relative to high forward-transferring data rate, such as cortical stimulation. Moreover, the employment of BPSK demodulation along with a passive modulation method allows full-duplex data communication between an external controller and the implantable device, which may improve the controllability and observability of the overall implanted system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A log-domain μbeamformer for medical ultrasound imaging systems

    Page(s): 2563 - 2575
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1352 KB) |  | HTML iconHTML  

    A fully differential, Class-AB, log domain microbeamformer has been designed in a 60 GHz Si-Ge BiCMOS process. The demonstrated microbeamformer has four input channels and four delays, though the concept can easily be extended to any desirable configuration. The log domain, Class-AB architecture is perfect for medical ultrasound applications due to the fact that the received ultrasound signal has very low amplitude during the major part of the reception period. This leads to very low power consumption because of the Class-AB configuration. The delay-line in the microbeamformer is constructed using a cascade of low input impedance allpass filter cells. A simple implementation of the zero in the allpass filter helps to keep the overall power consumption low. The delay of each allpass filter cell is programmable through the adjustment of a tuning current. Due to the Class-AB architecture used, every source signal must be shaped by a signal preconditioning circuit before connected to the filter cells. A well-known preconditioning circuit has been modified to increase the dynamic range. The modification introduces noise cancellation as well as a method to increases the maximum signal swing. The dynamic range of one preconditioning cell is shown to increase 12.6 dB compared to the classic translinear circuit at a penalty of 15% increase in the power consumption. Signal-to-noise ratio of one allpass filter cell is typically 56.5 dB, and the global dynamic range of the same cell is typically 63.8 dB at an average power consumption of 3.5 mW when 16 input signals are connected to the filter. The power consumption at maximum signal amplitude for the microbeamformer having four input channels and four delays is 3.2 mW with a supply voltage of 2.5 V. In the intended application, the quiescent power consumption is a much better description of the average power consumption. This power consumption is 1.3 mW. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A CMOS microcoil-associated preamplifier for NMR spectroscopy

    Page(s): 2576 - 2583
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1088 KB) |  | HTML iconHTML  

    For improving sensitivity of nuclear magnetic resonance (NMR) measurements, an in-field preamplifier in a low-cost CMOS process is presented. It is based on a second-generation positive current conveyor (CCII+), with an impedance-matching output stage. The circuit has been designed with optimization of key performances, such as bandwidth, noise, and offset voltage. There have also been precautions taken against potential effect of strong magnetic field under which the circuit should operate. The designed preamplifier has a voltage gain of 15 dB and a bandwidth of 100 MHz. After fabrication of the circuit, we have carried out testing work, including in-field circuit test and characterization of MOS transistors. Under 2-T magnetic field, there have not been substantial changes in overall circuit performances compared to results obtained by post-layout simulations. For an experiment of NMR measurements with and without in-field preamplifier, the circuit is coupled with a receiver micro-coil. The experiment has been to detect protons at 85.13-MHz resonance frequency under 2-T magnetic field with water sample. The obtained results have shown a 14-dB signal-to-noise ratio improvement when the preamplifier is associated with the receiver coil. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A 1-V analog CMOS front-end for detecting QRS complexes in a cardiac signal

    Page(s): 2584 - 2594
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB) |  | HTML iconHTML  

    A low-voltage low-power signal processing chip for electrocardiogram measurements has been designed and manufactured. The circuit includes a continuous time, offset-compensated preamplifier with an amplification of 40 dB, an eighth-order Butterworth switched-opamp switched-capacitor (SO-SC) filter with a passband of 8-30 Hz, a 32-kHz crystal oscillator, an SO-SC postamplifier, and a bias circuit. The whole circuit operates with supply voltages from 1.0 to 1.8 V and the measured average current consumption is only about 3 μA. The circuit is therefore very suitable for portable applications such as heart rate detectors. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Low-power low-voltage CMOS A/D sigma-delta modulator for bio-potential signals driven by a single-phase scheme

    Page(s): 2595 - 2604
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1120 KB) |  | HTML iconHTML  

    Since the 1970's, the analog switches in switched-capacitor (SC) circuits are operated by nonoverlapping bi-phase control signals (φ1, φ2). The nonoverlapping of these two phases is essential for successful SC operation since, a capacitor inside an SC circuit can discharge if two switches, driven by φ1 and φ2, are turned on simultaneously. Moreover, since 1983, two additional phases are generally used in many SC circuits, which consist of advanced versions of φ1 and φ2. These two additional phases overcome the problem of signal-dependent charge injection. This paper presents a low-power and low-voltage analog-to-digital (A/D) interface module for biomedical applications. This module provides an A/D conversion based on a mixed clock-boosting/switched-opamp (CB/SO) second-order sigma-delta (ΣΔ) modulator, capable of interfacing with several different types electrical signals existing in the human body, only by re-programming the output digital filter. The proposed ΣΔ architecture employs a novel single-phase scheme technique, which improves the dynamic performance and highly reduces the clocking circuitry complexity, substrate noise and area. Simulated results demonstrate that the signal integrity can be preserved by exploring the gap between the high conductance region of pMOS and nMOS switches at low power-supply voltages and the fast clock transitions that exist in advanced CMOS technologies. The mixed CB/SO architecture together with the overall distortion reduction resulting from using the proposed single-phase scheme, result that the dynamic range of the modulator is pushed closer to the theoretical limit of an ideal second-order ΣΔ modulator. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Power harvesting and telemetry in CMOS for implanted devices

    Page(s): 2605 - 2613
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1400 KB)  

    Implanted sensors offer many advantages to study and monitor the human body. Wires or batteries often compromise their usefulness. We describe a telemetry chip that by inductive coupling supplies power to and transmits digital data from an implantable sensor. The same two coils are used to transmit both power and data. The chip fabricated in 0.5-μm CMOS technology supplies 1.7 mA at 3.3 V, over a distance up to 25 mm between coils. Experiments emulating the effect of human tissue by introducing water bearing colloids between the two coils revealed a negligible loss of transfer efficiency. With modified Miller encoding, the data link attained 3 10-5 bit error rate at 10 kbps transmission speed over 25 mm distance. Repeated tests using the same colloids between coils resulted in a slight decrease in the signal to noise ratio of the data stream with increasing thickness. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A biochemical translinear principle with weak inversion ISFETs

    Page(s): 2614 - 2619
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    A weak inversion region is shown to exist in ion-sensitive field effect transistor (ISFET) sensors. It is therefore proposed that the ISFET and its chemically sensitive (ChemFET) counterparts be used as translinear elements in the synthesis of novel biochemical input stages which perform real-time mathematical manipulation of biochemical signals. A Biochemical Translinear Principle using weakly inverted ChemFETs is presented. A low-power current-mode input stage circuit is presented as an application of the principle. This yields a linear relation between drain current and hydrogen ion concentration valid over four decades. This paper demonstrates an important and necessary step toward biochemical VLSI. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A tissue impedance measurement chip for myocardial ischemia detection

    Page(s): 2620 - 2628
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (952 KB)  

    In this paper, the design of a specific integrated circuit for the measurement of tissue impedances is presented. The circuit will be part of a multi-micro-sensor system intended to be used in cardiac surgery for sensing biomedical parameters in living bodies. Myocardium tissue impedance is one of these parameters which allows ischemia detection. The designed chip will be used in a four-electrode based setup where the effect of electrode interfaces are cancelled by design. The chip includes a circuit to generate the stimulus signals (sinusoidal current) and the circuitry to measure the magnitude and phase of the tissue impedance. Several integrated circuits have been designed, fabricated and tested, in a 0.8-μm CMOS process, working at 3 V of power supply. Some of them including building blocks, and other with the whole measurement system. Experimental tests have shown the circuit feasibility giving expected results for both in-vitro and in-vivo test conditions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Architecture tradeoffs in high-density microstimulators for retinal prosthesis

    Page(s): 2629 - 2641
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2544 KB)  

    Electrical stimulation of the retinal layer inside the eye has been identified as a form of visual prosthesis to restore lost vision in blind patients affected by retinitis pigmentosa and age-related macular degeneration, through several studies and experiments. While initial clinical experiments using retinal prosthesis have resulted in visual perception in humans, psychophysical tests and simulations suggest that a high-density retinal prosthesis is required to restore vision to a level of reading and mobility. In the implanted prosthetic device, the microstimulator is functionally the closest to the tissue, delivering the electrical stimulation. Choosing the suitable architecture of the microstimulator requires the knowledge of the available choices and the tradeoffs associated with each of them. This paper presents the different architectures of microstimulator for high-density retinal prosthesis considering both the biomedical and circuit perspectives. The choices for the key aspects of the microstimulator-location of the chip in the eye, electrode configuration, method of stimulation, demultiplexing, stimulation sequence, and communication protocol-are discussed along with the associated tradeoffs for each of them. One of the architectures is used in a prototype microstimulator for an implantable epi-retinal prosthetic device to be used in clinical trials. The chip consists of 60 independently programmable output drivers for delivering electrical stimulus and digital controller for managing run-time and configuration data. The circuit details of the chip fabricated in 1.2-μm CMOS technology and its measurement results are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A near-infrared heart rate measurement IC with very low cutoff frequency using current steering technique

    Page(s): 2642 - 2647
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    A near-infrared heart-rate measurement IC that processes the photoplethysmographic signal was designed using a 0.35-μm CMOS technology. The IC consists of a current-to-voltage (I-V) converter, a buffer, a sample-and-hold circuit, a second-order continuous-time low-pass filter (CT-LPF), a comparator, and a timing circuit that is used to pulse the external light-emitting diode with a very low duty cycle to reduce its power consumption. The current steering technique is employed in the design of the CT-LPF to meet the requirement for very low cutoff frequency. The circuit operates from a 3-V lithium battery, occupies a core area of 0.46 mm2 and has a power consumption of 4.5 mW. The measurement results corroborate with simulation results and show that the CT-LPF can achieve a cutoff frequency of as low as 0.25 Hz. This demonstrates the feasibility of current steering technique in the design of filter for low-frequency application. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Visual neuroprosthesis: a non invasive system for stimulating the cortex

    Page(s): 2648 - 2662
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1600 KB)  

    This paper describes a complete visual neuroprosthesis wireless system designed to restore useful visual sense to profoundly blind people. This visual neuroprosthesis performs intracortical microstimulation through one or more arrays of microelectrodes implanted into the primary visual cortex. The whole system is composed by a primary unit located outside the body and a secondary unit, implanted inside the body. The primary unit comprises a neuromorphic encoder, a forward transmitter, and a backward receiver. The developed neuromorphic encoder generates the spikes to stimulate the cortex by approximating the spatio-temporal receptive fields characteristic response of ganglion cells. Power and stimuli information are carried to inside the cranium by means of a low-coupling transformer, which establishes a wireless inductive link between the two units. The secondary unit comprises a forward receiver, microelectrode stimulation circuitry and a backward transmitter that is used to monitor the implant. Address event representation is used for communicating spike events. Data is modulated with binary frequency-shift keying and differential binary phase-shift keying in the forward and in the backward directions, respectively. A prototype of the proposed system was developed and tested. Experimental results show that the spikes to stimulate the visual cortex are accurately generated and that the efficiency of the inductive link is relatively high, about 28% in average for 1 cm intercoil distance providing a power of about 50 milliwatts to the secondary implanted unit. Application specific integrated circuits were designed for this secondary unit, showing that, with current technology, it is possible to implement such a unit, respecting the power constraints. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new integrated front-end for a noninvasive brain imaging system based on near-infrared spectroreflectometry

    Page(s): 2663 - 2671
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1152 KB) |  | HTML iconHTML  

    In this paper, we present a fully integrated front-end of a portable spectroreflectometry-based brain imaging system dedicated for acquisition of modulated optical signals at a frequency of 1 Hz to 25 kHz. The proposed front-end preamplifier is composed of a photodetector, a transimpedance preamplifier, a two-stage voltage amplifier and a mixer. Strict constraints regarding noise thus have to be considered. The preamplifier consists of a transimpedance block featuring a 95-dBΩ gain and an average input current noise density at the frequency of interest of approximately 3 pA/√Hz. Each of the two subsequent voltage amplifiers allows the user to obtain an additional 25-dB gain. Considering the tuning capabilities and the losses due to the filters and the nonideal buffers, the proposed front-end allows us to obtain a total gain up to 145 dB. The back-end of the amplification chain is composed of a mixer which is used to produce a continuous voltage proportional to the amplitude of the input optical signals. All those features were integrated using CMOS 0.18-μm technology and the experimental results are in agreement with the initial design requirements. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Mini-FDPM and heterodyne mini-FDPM: handheld non-invasive breast cancer detectors based on frequency-domain photon migration

    Page(s): 2672 - 2685
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2200 KB) |  | HTML iconHTML  

    This paper describes a handheld instrument for noninvasive detection of breast cancer based on a broad-band optical spectroscopy technique called frequency-domain photon migration (FDPM). It performs broad-band modulation on the intensity of near-infrared laser diodes and derives the scattering and absorption coefficients of the bulk tissue from phase and amplitude data measurements. Two different schematics of mini-FDPM were designed and fabricated. One is a homodyne structure that performs direct comparison of modulated and demodulated frequencies, and the other is a heterodyne structure that compares downconverted demodulated frequencies. The former has a simple structure but lower accuracy due to noise. The latter is more complex but more accurate due to the filtering of noise. The miniature size makes it possible to eliminate fiberoptic cables and enables direct contact between the laser diode and the tissue, making the instrument more power efficient while enhancing detection capabilities. Measurement results show that these miniature systems match or outperform the current prototype while costing two orders of magnitude less. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Digital implementation of a wavelet-based event detector for cardiac pacemakers

    Page(s): 2686 - 2698
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (896 KB)  

    This paper presents a digital hardware implementation of a novel wavelet-based event detector suitable for the next generation of cardiac pacemakers. Significant power savings are achieved by introducing a second operation mode that shuts down 2/3 of the hardware for long time periods when the pacemaker patient is not exposed to noise, while not degrading performance. Due to a 0.13-μm CMOS technology and the low clock frequency of 1 kHz, leakage power becomes the dominating power source. By introducing sleep transistors in the power-supply rails, leakage power of the hardware being shut off is reduced by 97%. Power estimation on RTL-level shows that the overall power consumption is reduced by 67% with a dual operation mode. Under these conditions, the detector is expected to operate in the sub-μW region. Detection performance is evaluated by means of databases containing electrograms to which five types of exogenic and endogenic interferences are added. The results show that reliable detection is obtained at moderate and low signal to noise-ratios (SNRs). Average detection performance in terms of detected events and false alarms for 25-dB SNR is PD=0.98 and PFA=0.014, respectively. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A sparse Bayesian method for determination of flexible design matrix for fMRI data analysis

    Page(s): 2699 - 2706
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB) |  | HTML iconHTML  

    The construction of a design matrix is critical to the accurate detection of activation regions of the brain in functional magnetic resonance imaging (fMRI). The design matrix should be flexible to capture the unknown slowly varying drifts as well as robust enough to avoid overfitting. In this paper, a sparse Bayesian learning method is proposed to determine a suitable design matrix for fMRI data analysis. Based on a generalized linear model, this learning method lets the data itself determine the form of the regressors in the design matrix. It automatically finds those regressors that are relevant to the generation of the fMRI data and discards the others that are irrelevant. The proposed approach integrates the advantages of currently employed methods of fMRI data analysis (the model-driven and the data-driven methods). Results from the simulation studies clearly reveal the superiority of the proposed scheme to the conventional t-test method of fMRI data analysis. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Applications and improvement of H.264 in medical video compression

    Page(s): 2707 - 2716
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1416 KB)  

    This paper aims at applying H.264 in medical video compression applications and improving the H.264 rate control algorithm with better perceptual quality. First, H.264 is briefly reviewed and introduced to the area of medical video compression. Second, a new motion complexity (MC) measure is defined to express the complexity of motion contents in a video frame, and a new H.264 rate control scheme with the MC measure and perceptual bit allocation is proposed for medical video compression. Third, two sets of experiments are conducted: the comparison between MPEG-4 and H.264, and the comparison between JVT-H014 , which is the H.264 adopted rate control algorithm, and our proposed rate control scheme. The first set of experiments shows that compared with MPEG-4, H.264 can achieve a significant average peak signal-to-noise ratio (PSNR) gain of up to 4.35 dB for the test medical video sequences, and thus is much more effective when applied in medical video compression. The second set of experiments shows that compared with H014, the proposed rate control scheme can achieve better perceptual video quality, with an average PSNR gain of up to 0.19 dB for the test medical video sequences. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Block-level parallel processing for scaling evenly divisible images

    Page(s): 2717 - 2725
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB) |  | HTML iconHTML  

    Image scaling is a frequent operation in medical image processing. This paper presents how two-dimensional (2-D) image scaling can be accelerated with a new coarse-grained parallel processing method. The method is based on evenly divisible image sizes which is, in practice, the case with most medical images. In the proposed method, the image is divided into slices and all the slices are scaled in parallel. The complexity of the method is examined with two parallel architectures while considering memory consumption and data throughput. Several scaling functions can be handled with these generic architectures including linear, cubic B-spline, cubic, Lagrange, Gaussian, and sinc interpolations. Parallelism can be adjusted independent of the complexity of the computational units. The most promising architecture is implemented as a simulation model and the hardware resources as well as the performance are evaluated. All the significant resources are shown to be linearly proportional to the parallelization factor. With contemporary programmable logic, real-time scaling is achievable with large resolution 2-D images and a good quality interpolation. The proposed block-level scaling is also shown to increase software scaling performance over four times. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • EEG-based drowsiness estimation for safety driving using independent component analysis

    Page(s): 2726 - 2738
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1968 KB) |  | HTML iconHTML  

    Preventing accidents caused by drowsiness has become a major focus of active safety driving in recent years. It requires an optimal technique to continuously detect drivers' cognitive state related to abilities in perception, recognition, and vehicle control in (near-) real-time. The major challenges in developing such a system include: 1) the lack of significant index for detecting drowsiness and 2) complicated and pervasive noise interferences in a realistic and dynamic driving environment. In this paper, we develop a drowsiness-estimation system based on electroencephalogram (EEG) by combining independent component analysis (ICA), power-spectrum analysis, correlation evaluations, and linear regression model to estimate a driver's cognitive state when he/she drives a car in a virtual reality (VR)-based dynamic simulator. The driving error is defined as deviations between the center of the vehicle and the center of the cruising lane in the lane-keeping driving task. Experimental results demonstrate the feasibility of quantitatively estimating drowsiness level using ICA-based multistream EEG spectra. The proposed ICA-based method applied to power spectrum of ICA components can successfully (1) remove most of EEG artifacts, (2) suggest an optimal montage to place EEG electrodes, and estimate the driver's drowsiness fluctuation indexed by the driving performance measure. Finally, we present a benchmark study in which the accuracy of ICA-component-based alertness estimates compares favorably to scalp-EEG based. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

The theory, analysis, design, and practical implementations of circuits, and the application of circuit techniques to systems and to signal processing.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Shanthi Pavan
Indian Institute of Technology, Madras