Effect Of Calibration Errors Research Articles

Observing the reionization: effect of calibration and position errors on realistic observation conditions

ABSTRACT Observation of the redshifted 21-cm signal from Cosmic Dawn and Epoch of Reionization is a challenging endeavor in observational cosmology. Presence of orders of magnitude brighter astrophysical foregrounds and various instrumental systematics increases the complexity of these observations. This work presents an end-to-end pipeline dealing with synthetic interferometric data of sensitive radio observations. The mock sky model includes the redshifted 21-cm signal and astrophysical foregrounds. The effects of calibration error and position error in the extraction of the redshifted 21-cm power spectrum has been simulated. The effect of the errors in the image plane detection of the cosmological signal has also been studied. A comparative analysis for array configurations like the SKA1-Low, MWA, and HERA has been demonstrated. The calibration error tolerance of the arrays, under some assumptions about the nature of the systematic components, is optimally found to be $\sim 0.01{{\ \rm per\ cent}}$ for the detection of the signal. For position errors, an offset of ⪆5 arcsec makes the residual foregrounds obscure the target signal. These simulations also imply that the SKA-1 Low performs marginally better than the other telescopes in the image domain. The same is true for MWA in the power spectrum domain. This is one of the first studies that compares performance of various radio telescopes operating under similar observing conditions towards detecting the cosmological signal. This end-to-end pipeline can also be extended to study effects of chromatic primary beam, radio frequency inferences, foregrounds with spectral features, etc.

标定误差对色散条纹共相误差检测影响的修正

标定误差对色散条纹共相误差检测影响的修正

Effect of Calibration Error on Bone Tracking Accuracy With Fluoroscopy

Model-based 3D-fluoroscopy can quantify joint kinematics with 1 mm and 1 deg accuracy level. A calibration based on the acquisition of devices of known geometry is usually applied to size the system. This study aimed at quantifying the sensitivity of the fluoroscopic pose estimation accuracy specifically to errors in the calibration process, excluding other sources of error. X-ray focus calibration error was quantified for different calibration setups, and its propagation to the pose estimation was characterized in-silico. Focus reference position influenced the calibration error dispersion, while calibration cage pose affected its bias. In the worst-case scenario, the estimation error of the principal point and of the focus distance was lower than 1 mm and 2 mm, respectively. The consequent estimation of joint angles was scarcely influenced by calibration errors. A linear trend was highlighted for joint translations, with a sensitivity proportional to the distance between the model and the image plane, resulting in a submillimeter error for realistic calibration errors. The biased component of the error is compensated when computing relative joint kinematics between two segments.

Effect of calibration errors on Bayesian parameter estimation for gravitational wave signals from inspiral binary systems in the advanced detectors era: Further investigations

By 2015, the advanced versions of the gravitational wave detectors Virgo and LIGO will be online. They will collect data in coincidence with enough sensitivity to potentially deliver multiple detections of gravitational waves from inspirals of compact-object binaries. In a previous work, we have studied the effects introduced in the estimation of the physical parameters of the source by uncertainties in the calibration of the interferometers. Our bias estimator for parameter errors introduced by calibration uncertainties consisted of two terms: A genuine bias due to the calibration errors, and a contribution coming from the limited number of samples used to explore the parameter space. In this article, we have focused on this second term, and we have shown how it is smaller than the former (about 10 times smaller), and how it decreases as the signal-to-noise ratio increases.

Effect of Calibration Error on Reconstruction Accuracy of Stereovision System

This paper investigates the relation between the calibration error and reconstruction accuracy of stereovision system through simulation experiment. According to the model of a typical non-parallel stereovision system, an array of points in the common view field of the two cameras is projected onto the image plane of the left and right camera respec- tively, forming the left image and right image. After changing the calibration parameter slightly around its ground truth, the array of points is reconstructed. By comparing the reconstruction result of the points in the array with their original position, the major factors affecting reconstruction accuracy are summarized, which include the abscissa of the principal point, the component of the rotation vector along the ordinate axis, the first order radial distortion coefficient, the compo- nent of the translation vector along the abscissa axis, and the abscissa of the principal length. Especially, the abscissa of the principal point and the component of the rotation vector along the ordinate axis have prominent effect on reconstruc- tion accuracy. In the process of calibration, the error of the major factors must be controlled strictly, so that the accuracy requirement of the stereovision system can be satisfied.

Effect of calibration errors on Bayesian parameter estimation for gravitational wave signals from inspiral binary systems in the advanced detectors era

By 2015 the advanced versions of the gravitational-wave detectors Virgo and LIGO will be online. They will collect data in coincidence with enough sensitivity to potentially deliver multiple detections of gravitation waves from inspirals of compact-object binaries. This work is focused on understanding the effects introduced by uncertainties in the calibration of the interferometers. We consider plausible calibration errors based on estimates obtained during LIGO's fifth and Virgo's third science runs, which include frequency-dependent amplitude errors of $\sim 10%$ and frequency-dependent phase errors of $\sim 3$ degrees in each instrument. We quantify the consequences of such errors estimating the parameters of inspiraling binaries. We find that the systematics introduced by calibration errors on the inferred values of the chirp mass and mass ratio are smaller than 20% of the statistical measurement uncertainties in parameter estimation for 90% of signals in our mock catalog. Meanwhile, the calibration-induced systematics in the inferred sky location of the signal are smaller than $\sim 50%$ of the statistical uncertainty. We thus conclude that calibration-induced errors at this level are not a significant detriment to accurate parameter estimation.

An Interpolation-Based Calibration Architecture for Pipeline ADC With Nonlinear Error

The linearity of a pipeline analog-to-digital converter (ADC) is mainly limited by capacitor mismatch and finite operational amplifier (OPAMP) gain, which cause large power and design difficulty in modern nanometer CMOS processes for high-resolution pipeline ADCs. It is a trend of developing digital calibration techniques to compensate the analog error in pipeline stages. This paper systematically introduces a novel interpolation-based digital calibration architecture to compensate both linear and nonlinear errors from pipeline stages. The new method does not require convergence. The effect of calibration error is analyzed in detail in this paper. A prototype 20-MS/s pipeline ADC is fabricated in a 0.35-μm 3.3-V CMOS process. For 12-b resolution, the digital calibration improves the ADC differential nonlinearity and integral nonlinearity from 1.47 LSB and 7.85 LSB to 0.2 LSB and 0.27 LSB. For a 590-kHz sinusoidal signal, the calibration improves the ADC signal-to-noise-distortion ratio and spurious-free dynamic range from 41.3 dB and 52.1 dB to 72.5 dB and 84.4 dB, respectively. With the new calibration technique, low-gain OPAMPs and small capacitors are used in the pipeline. The designed ADC has 0.78-pJ/step figure of merit (FOM), which is among the lowest reported FOMs for high-resolution pipeline ADC designs. The new architecture requires an accurate calibration ADC (CalADC) and two digital decoders. CalADC is implemented on-chip with 6.5% die area and 8.9% power. The decoders are synthesized to have 912 gates and consume 23.4% ADC power.

An End-to-End Error Model for Classification Methods Based on Temporal Change or Polarization Ratio of SAR Intensities

This paper aims at defining the expression of the probability of error of classification methods using a synthetic aperture radar (SAR) intensity ratio as a classification feature. The two SAR intensities involved in this ratio can be measurements from different dates, polarizations, or, also possibly, frequency bands. Previous works provided a baseline expression of the probability of error addressing the two-class problem with equal a priori class probabilities and no calibration error. This study brings up a novel expression of the error, providing the possibility to assess the effect of class probabilities and calibration errors. An extended expression is described for the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$n$</tex> </formula> -class problem. The effect of calibration errors such as channel gain imbalance, radiometric stability, and crosstalk is assessed in the general case. The results indicate that, for the applications under study, channel gain imbalance is usually not a decisive parameter, but radiometric stability is more critical in methods based on the temporal change. Crosstalk has a negligible effect in the case of copolarizations. The impacts of other system parameters, such as ambiguity ratio, time-lapse between repeat-pass orbits, spatial resolution, and number of looks, are illustrated through a set of assumptions on the backscattering values of the considered classes. The model is validated by comparing some of its outputs to experimental results calculated from the application of rice fields mapping methods on real data. This error model constitutes a tool for the design of future SAR missions and for the development of robust classification methods using existing SAR instruments.

The effect of calibration errors on the accuracy of the eye movement recordings

For calibrating eye movement recordings, a regression between spatially defined calibration points and corresponding measured raw data is performed. Based on this regression, a confidence interval (CI) of the actually measured eye position can be calculated in order to quantify the measurement error introduced by inaccurate calibration coefficients. For calculating this CI, a standard deviation (SD) - depending on the calibration quality and the design of the calibration procedure - is needed. Examples of binocular recordings with separate monocular calibrations illustrate that the SD is almost independent of the number and spatial separation between the calibration points – even though the later was expected from theoretical simulation. Our simulations and recordings demonstrate that the SD depends critically on residuals at certain calibration points, thus robust regressions are suggested.

램프 로드/언로드 하드디스크 드라이브의 역기전력을 이용한 VCM 속도제어

Since most of small form-factor drives have a load/unload mechanism and the flying height of the head is getting lower as the capacity of disk drives increases, the load/unload velocity becomes one of the important factors to ensure the reliability of the load/unload mechanism. To control the load/unload velocity accurately, velocity sensing is essential. In this paper, we introduce a very practical method that acquires the load/unload velocity from the back electromotive force (BEMF) of a voice coil motor (VCM) and propose a calibration method for measuring the BEMF from a given circuit. Moreover, the effect of calibration error and temperature variation on the measurement of BEMF is shown by simulation. Then, this present method is applied to the load/unload velocity controller and is verified from the experimental result.