Digital Error Research Articles

SAR ADC Algorithm with Redundancy and Digital Error Correction

This paper describes an algorithm for Successive Approximation Register (SAR) ADCs with overlapping steps that allow comparison decision errors (due to, such as DAC incomplete settling) to be digitally corrected. We generalize this non-binary search algorithm, and clarify which decision errors it can digitally correct. This algorithm requires more SAR ADC conversion steps than a binary search algorithm, but we show that the sampling speed of an SAR ADC using this algorithm can be faster than that of a conventional binary-search SAR ADC—because the latter must wait for the settling time of the DAC inside the SAR ADC.

Study of image characteristics on digital image correlation error assessment

In this paper, errors related to digital image correlation (DIC) technique applied to measurements of displacements are estimated. This work is based on the generation of synthetic images representative of real speckle patterns. With these images, various parameters are treated in order to determine their impact on the measurement error. These parameters are related to the type of deformation imposed on the speckle, the speckle itself (encoding of the image and image saturation) or the software (subset size).

A Feasibility Assessment for Low-Cost InSAR Formation-Flying Microsatellites

Multistatic interferometric synthetic aperture radar (InSAR) is a promising potential payload for a small satellite constellation. CanX-4 and CanX-5 are a pair of formation-flying nanosatellites launching in 2009; once formation flight has been demonstrated, a future multistatic InSAR constellation of low-cost microsatellites can exploit subcentimeter intersatellite baseline knowledge, with digital elevation map height errors on the order of 1 m in the flat-terrain case. This paper evaluates the feasibility of such a mission, using case studies of commonly proposed configurations: the Interferometric Cartwheel, the Cross-Track Pendulum, and the Cartwheel-Pendulum (Car-Pe) configuration. In each case, several SAR transmitters are considered: L-, C-, and X-band transmitters with parameters mirroring existing ldquolargerdquo satellite SAR missions, and a theoretical X-band microsatellite transmitter. The available interferometric baselines, ground coverage, and image resolutions are evaluated in each scenario. The X-band ldquomicrordquo transmitter is feasible, but the low transmit power severely limits the ground coverage. The X-band ldquolargerdquo transmitter provides the largest ground coverage and the highest resolution along with the X-band ldquomicrordquo option. The resolutions are wavelength dependent and remain relatively constant among the configurations. The operating areas of the pendulum demonstrate the largest degree of overlap, while the longer along-track baselines of the cartwheel result in a smaller overlap. Both two-receiver (pendulum and cartwheel) configurations demonstrate baseline characteristics that may be optimal for different applications, while the three-receiver Car-Pe demonstrates the advantages of both the pendulum and cartwheel.

Effect of Different Larval Rearing Temperatures on the Productivity (Ro) and Morphology of the Malaria VectorAnopheles superpictusGrassi (Diptera: Culicidae) Using Geometric Morphometrics

Effect of Different Larval Rearing Temperatures on the Productivity (R_o) and Morphology of the Malaria Vector<i>Anopheles superpictus</i>Grassi (Diptera: Culicidae) Using Geometric Morphometrics

Current mode ADC design in a 0.5-μm CMOS process

This paper presents a pipelined current mode analog to digital converter (ADC) designed in a 0.5-μm CMOS process. Adopting the global and local bias scheme, the number of interconnect signal lines is reduced numerously, and the ADC exhibits the advantages of scalability and portability. Without using linear capacitance, this ADC can be implemented in a standard digital CMOS process; thus, it is suitable for applications in the system on one chip (SoC) design as an analogue IP. Simulations show that the proposed current mode ADC can operate in a wide supply range from 3 to 7 V and a wide quantization range from ±64 to ±256 μA. Adopting the histogram testing method, the ADC was tested in a 3.3 V supply voltage/±64 μA quantization range and a 5 V supply voltage/±256 μA quantization range, respectively. The results reveal that this ADC achieves a spurious free dynamic range of 61.46 dB, DNL/INL are −0.005 to +0.027 LSB/–0.1 to +0.2 LSB, respectively, under a 5 V supply voltage with a digital error correction technique.

The fractional frequency synthesizer with coincidence mixer

In this paper, a fractional frequency synthesizer architecture is proposed, employing a new mixer based on signal coincidence, which achieves fast-settling, and high resolution compared with the direct frequency synthesizer based on diophantine equations. This new coincidence mixer, using digital error correction techniques, requires no output filters where sum and difference of input signal frequencies are obtained directly by separated outputs. Besides some examples, related to synthesizers the simulations are performed by using Matlab. The new coincidence mixer is also realized and the measuring results are also given.

Sustainable development and planning in the case of uncertainty in Digital Elevation Models

The existence of elevation errors in Digital Elevation Models (DEMs) is usually ignored during spatial analysis of problems concerning planning through a sustainable sense of development. Examples of such analyses are: slope analysis for site selection, designing infrastructure works on physical terrains, 3D calculations on a basic surface like the terrain, sitting and zoning defi nition through elevation, etc. As a result, conclusions are extracted, decisions are made and actions are designed and executed, while the problem is examined theoretically, away from reality. This article describes the attempt to introduce a new model, the Digital Elevation Error Model, which incorporates elevation uncertainty and fuzziness, and accompanies a DEM, uniquely. The use of uncertain terrains combined with a probabilistic soft-decision theory, eliminates the risk of taking decisions that do not apply to the real problem under examination. The research on this subject has shown deviations from the results, from those of a hard-decision theory, up to 20‐50% for volume measurements, area measurements, defi nition of boundaries, visibility calculations, etc. The absence of an integrated geographic information system, able to manage data uncertainty, makes it necessary to use alternative approaches to the problem but not the

Phase noise optimization in temporal phase-shifting digital holography with partial coherence light sources and its application in quantitative cell imaging

In temporal phase-shifting-based digital holographic microscopy, high-resolution phase contrast imaging requires optimized conditions for hologram recording and phase retrieval. To optimize the phase resolution, for the example of a variable three-step algorithm, a theoretical analysis on statistical errors, digitalization errors, uncorrelated errors, and errors due to a misaligned temporal phase shift is carried out. In a second step the theoretically predicted results are compared to the measured phase noise obtained from comparative experimental investigations with several coherent and partially coherent light sources. Finally, the applicability for noise reduction is demonstrated by quantitative phase contrast imaging of pancreas tumor cells.

Dual-Mode Multiple-Band Digital Controller for High-Frequency DC–DC Converter

An integrated digital controller design for dc-dc converter is proposed in this paper. The proposal presents a multiple- band dual-stage (MBDS) delay line A/D converter (ADC) for wide dynamic range of operation with reduced ripple, chip area, and power consumption. This proposal also introduces a novel folding logic for digital error calculation and dual-mode error control PID for improving transient response. A complete closed-loop experimental prototype is demonstrated on a field-programmable-gate- array-based setup. The feasibility and functionality of the proposed digital controller is verified with a closed-loop synchronous buck converter prototype that switches at 1 MHz and regulates over a wide output voltage range of 1.6-3.3 V. The proposed MBDS delay line ADC is fabricated with discrete logic gates and flip-flops. The integrated digital controller is also implemented using standard cell-based design methodology in 0.5-mum CMOS technology. The design reduces 33 % on-chip area compared to an equivalent of 64 tap delay line ADC. The complete digital controller chip takes less than 0.7 mm2 of silicon area and consumes an average current of 92 muA at 1-MHz switching frequency. The voltage-mode digital loop achieves tracking time of less than 10 mus for 1-V step change of the reference voltage and settling time of 20 mus. Post layout simulation and experimental results are demonstrated.

Influence of digital camera errors on the photogrammetric image processing

The paper deals with the calibration of digital camera Canon EOS 350D, often used for the photogrammetric 3D digitalisation and measuring industrial and construction site objects. During the calibration data of the optical and electronic parameters, influencing the distortion of images, such as correction of the principal point, focal length of the objective, radial symmetrical and non-symmetrical distortions were obtained. The calibration was performed by means of the Tcc software implementing the polynomial of Chebichev and using a special test-field with the marks, the coordinates of which are precisely known. The main task of the research is to determine, how parameters of the camera calibration influence the processing of images, i.e. the creation of geometric model, the results of triangulation calculations and stereo-digitalisation. Two photogrammetric projects were created for this task. In the first the project non-corrected and in the second the corrected ones, considering the optical errors of the camera obtained during the calibration, images were used. The results of analysis of figures processing is shown in figures and tables. The conclusions are presented. Article in English Skaitmeninės fotokameros optikos klaidų įtaka atliekant fotogrametrinį nuotraukų apdorojimą Santrauka. Straipsnyje aprašytas skaitmeninės matuojamosios fotokameros Canon EOS 350D, dažnai naudojamos trimačiam arba dvimačiam fotogrametriniam objektų skaitmeninimui bei matavimams, kalibravimo procesas, kurio metu gauti objektyvo optikos sistemos parametrų duomenys – pagrindinio taško pataisa, objektyvo židinio nuotolis, radialinės simetrinės ir nesimetrinės distorsijos. Kalibravimas atliktas Tcc vokiška programa pagal Čebyševo polinomą, naudojant specialų erdvinį stendą su žinomomis pažymėtų taškų koordinatėmis. Tyrimo tikslas – nustatyti, kokios įtakos fotokameros kalibravimo parametrai turi fotonuotraukų apdorojimo, tai yra geometrinio modelio sudarymo, trianguliacijos skaičiavimų ir stereovektorizavimo rezultatams. Šiam tikslui sukurti du projektai. Pirmajame naudojamos fotonuotraukos, kuriose fotokameros objektyvo klaidos netaisytos, antrajame – pataisytos. Fotonuotraukų apdorojimo analizės rezultatai pateikti paveiksluose bei lentelėse.

Power Dissipation Bounds for High-Speed Nyquist Analog-to-Digital Converters

A very important limitation of high-speed analog-to-digital converters (ADCs) is their power dissipation. ADC power dissipation has been examined several times, mostly empirically. In this paper, we present an attempt to estimate a lower bound for the power of ADCs, based on first principles and using pipeline and flash architectures as examples. We find that power dissipation of high-resolution ADCs is bound by noise, whereas technology is the limiting factor for low-resolution devices. Our model assumes the use of digital error correction, but we also study an example on the power penalty due to matching requirements. A comparison with published experimental data indicates that the best ADCs use about 50 times the estimated minimum power. Two published ADCs are used for a more detailed comparison between the minimum bound and today's designs.

Digital error correction technique for binary decision successive approximation ADCs

A digital error correction technique with negligible hardware overhead is proposed for binary successive approximation ADCs. A redundant decision phase is inserted between the normal SAR operations, and the coarse decision error caused by incomplete DAC settling is corrected by a digital code addition. The relaxed DAC settling requirement for coarse decision increases the conversion speed.

Assessment of Digital Image Correlation Measurement Errors: Methodology and Results

Optical full-field measurement methods such as Digital Image Correlation (DIC) are increasingly used in the field of experimental mechanics, but they still suffer from a lack of information about their metrological performances. To assess the performance of DIC techniques and give some practical rules for users, a collaborative work has been carried out by the Workgroup “Metrology” of the French CNRS research network 2519 “MCIMS (Mesures de Champs et Identification en Mécanique des Solides / Full-field measurement and identification in solid mechanics, http://www.ifma.fr/lami/gdr2519 )”. A methodology is proposed to assess the metrological performances of the image processing algorithms that constitute their main component, the knowledge of which being required for a global assessment of the whole measurement system. The study is based on displacement error assessment from synthetic speckle images. Series of synthetic reference and deformed images with random patterns have been generated, assuming a sinusoidal displacement field with various frequencies and amplitudes. Displacements are evaluated by several DIC packages based on various formulations and used in the French community. Evaluated displacements are compared with the exact imposed values and errors are statistically analyzed. Results show general trends rather independent of the implementations but strongly correlated with the assumptions of the underlying algorithms. Various error regimes are identified, for which the dependence of the uncertainty with the parameters of the algorithms, such as subset size, gray level interpolation or shape functions, is discussed.

Correlation-Based Carrier Phase Estimation for WDM DP-QPSK Transmission

A novel algorithm for frequency offset compensation and carrier phase estimation in systems with 40 or 111 Gb/s coherent dual-polarization quadrature phase-shift keying (DP-QPSK) with on-off keying or DP-QPSK neighbors is demonstrated. The algorithm, which applies correlation phase adjustment embedded between digital differential demodulation and nonredundant error correction, leads to a significant performance improvement over standard algorithms.

A Virtual Differential Map-Matching Algorithm with Improved Accuracy and Computational Efficiency

This paper presents development and application of a real-time virtual differential map-matching approach which makes use of the slow drifting property of the GPS errors and the continuous and gradual evolving characteristic of map errors to improve the accuracy and computational efficiency. A differential vector is created to approximate the real-time deviation, which is corrected continuously along with the vehicle movement during the map-matching process. Real-life application of the algorithm to the City of Hefei, a metropolis of China, shows that it corrects both GPS errors and digital map errors reasonably well with improved computational efficiency.

Impact of Terminal Digit Preference by Family Physicians and Sphygmomanometer Calibration Errors on Blood Pressure Value: Implication for Hypertension Screening

The accuracy of blood pressure (BP) measurement is important; systematic small errors can mislabel BP status in many persons. The objective of this study was to assess the impact of 2 types of measurement errors on the evaluation of BP in family medicine: errors associated with terminal digit preference and those associated with calibration errors of sphygmomanometers. Secondary data analyses from 2 different projects were used to derive empiric distributions of terminal digit and BP device errors. Taking into account both types of errors, the proportion of false positives (falsely high BP) and false negatives (falsely normal BP) varied between 0. 82% and 5.18% of the population of consulting family physicians. In the United States, false positives and false negatives in patients' BP evaluations might lead to overtreating or undertreating 1.15 million to 7.25 million patients. Results support the need for the development of systematic interventions for quality control of BP measurements and periodic retraining for health professionals.

Removal of digitization errors in fingerprint ridgelines using B-splines

Most of the contemporary automatic fingerprint identification systems (AFIS) are based on a dual strategy of combining the minutiae information with the ridge topography in order to improve the overall matching performance. To ensure the efficiency and robustness of such an AFIS, it is necessary, therefore, to rectify the abnormalities or aberrations of the underlying ridge topography, in general, and to smoothen the uneven/noisy ridgelines, in particular. The proposed work deals with one such problem besetting fingerprint analysis—the problem of eliminating digitization errors that usually creep in during fingerprint acquisition or during preprocessing. The method mainly involves fitting of B-splines for a set of control points chosen appropriately for each ridgeline in a fingerprint image. These fitted splines, in turn, can be used to reconstruct the concerned fingerprint, which, after the rectification procedure, becomes almost devoid of such digitization error. With a proper “smoothness parameter” that determines the extent to which a ridgeline is smoothed, the structural information of the corrected ridgelines produces improved results on fingerprint matching. Experimental results on several databases have been reported, which clearly demonstrate the strength and elegance of the proposed algorithm.

Stochastic vector mapping-based feature enhancement using prior-models and model adaptation for noisy speech recognition

This paper presents an approach to feature enhancement for noisy speech recognition. Three prior-models are introduced to characterize clean speech, noise and noisy speech, respectively. Sequential noise estimation is employed for prior-model construction based on noise-normalized stochastic vector mapping. Therefore, feature enhancement can work without stereo training data and manual tagging of background noise type based on the auto-clustering on the estimated noise data. Environment model adaptation is also adopted to reduce the mismatch between training data and test data. For the evaluation on the AURORA2 database, the experimental results indicate that a 9.6% relative reduction in digit error rate for multi-condition training and a 3.5% relative reduction in digit error rate for clean speech training were achieved without stereo training data compared to the SPLICE-based approach. For MATBN Mandarin broadcast news database with multi-condition training, a 13% relative reduction in syllable error rate for anchor speech, a 12% relative reduction in syllable error rate for field reporter speech and a 7% relative reduction in syllable error rate for interviewee speech were obtained compared to the MCE-based approach.

A study on the exaggeration(enlargement) of graphic data for the visual inspection of the digital map errors

A study on the exaggeration(enlargement) of graphic data for the visual inspection of the digital map errors

Continuous Characterization of the Planform Geometry and Curvature of Meandering Rivers

The complex feedback between process and form that governs planform migration of meandering rivers is still incompletely understood. Current theoretical models aimed at predicting planform migration relate the rate of meander migration at a particular location to the channel curvature at and upstream of that location. However, these models are still incapable of reproducing complex forms of bend development, such as compound loops. Evaluation of such models requires a representation of planform curvature better than that provided by traditional methods where the curvature is calculated from directional change between the successive digitized points—an approach that provides a discrete representation of curvature dependent on the density of the digitized points used to characterize the channel planform. This article presents and evaluates a methodology that provides a continuous functional representation of the planform geometry and curvature of meandering rivers. The method involves the fitting of splines, specifically parametric cubic splines (PCSs), to discrete digitization data of the channel centerline (CL) and the arc‐length parameterization of the resulting composite curve. The arc‐length parameterized PCS‐interpolated curve is then used to compute analytically the channel CL location and curvature for any value of the streamwise axis. Evaluation of the method involves examination of the effects of digitization interval size and digitization error on the characterization of the planform geometry and curvature using PCS fitting. The derivation of curvature values from continuous planform function for any location and any spatial interval overcomes the reliance either on average bend curvature values or on discrete curvature values based on digitized points.