Efficient digital self-calibration of video-rate pipeline ADCs using white gaussian noise

Proceedings of IEEE, ISCAS 2003, Vol.I, pp. 877-880A digital-domain self-calibration technique for video-rate pipeline A/D converters based on a white Gaussian noise input signal is presented. The implementation of the proposed algorithm requires simple digital circuitv. An application design example of the self-calibration of a IZb. 40 MUS CMOSpipeline ADC is shown to illustrate that the overall linearity of the ADC can be highly improved using this technique

Microfluidic device for refractive index measurement of fluid sample

AbstractThis paper represents a novel microfluidic device for simple refractive index (RI) measurement of fluid sample with sub microliter volume. The defocusing imaging technique using a three pinhole aperture plate is implemented for the refractive index measurement. For the self-calibration, the microfluidic device has a measurement region and a self-calibration region, and both regions are designed to be captured on single image frame. Thus, the refractive index of a sample fluid is automatically calculated with the self-calibration. For the demonstration of the proposed device, standard refractive index liquids with the refractive indices of 1.300, 1.400, 1.500, 1.600 and 1.700 are used. The measured refractive index has the maximum deviation of 0.0036 (0.24%) from the standard refractive index values

Novel ideas and techniques for large dark matter detectors

As dark matter detection experiments continue to report null results, the need for larger and more sensitive detectors means even more stringent design requirements. New calibration techniques are required and better calibration methods become possible with increased detector size. Additionally, previously ignored detector features such as convection become important, especially as internal, dissolvable sources become more common. Furthermore, convection also offers the possibility for reduction of the 222Rn backrounds via an offline analysis where atoms of 214Pb are tagged and followed throughout the detector via a technique dubbed the “radon self-veto”. In this thesis, we present the characterization of a deuterium-deuterium plasma fusion neutron generator optimized to perform the nuclear recoil calibration of XENON1T. Part of this characterization is done with liquid organic scintillator detectors, which are sensitive to both electonic and nuclear recoil interactions. We develop a new algorithm for discriminating between these two signal types using Laplace transforms and show that it performs better than traditional algorithms. A multipurpose source of dissolvable 220Rn is presented and measurements made of long-lived contaminants from this source. Finally, we present the first measurement of convection in XENON1T and report the results of a simple convection-agnostic implementation of the radon self-veto

Where is the fuzz? Undetected Lyman alpha nebulae around QSOs at z~2.3

We observed a small sample of 5 radio-quiet QSOs with integral field spectroscopy to search for possible extended emission in the Ly$\alpha$ line. We subtracted the QSO point sources using a simple PSF self-calibration technique that takes advantage of the simultaneous availability of spatial and spectral information. In 4 of the 5 objects we find no significant traces of extended Ly$\alpha$ emission beyond the contribution of the QSO nuclei itself, while in UM 247 there is evidence for a weak and spatially quite compact excess in the Ly$\alpha$ line at several kpc outside the nucleus. For all objects in our sample we estimated detection limits for extended, smoothly distributed Ly$\alpha$ emission by adding fake nebulosities into the datacubes and trying to recover them after PSF subtraction. Our observations are consistent with other studies showing that giant Ly$\alpha$ nebulae such as those found recently around some quasars are very rare. Ly$\alpha$ fuzz around typical radio-quiet QSOs is fainter, less extended and is therefore much harder to detect. The faintness of these structures is consistent with the idea that radio-quiet QSOs typically reside in dark matter haloes of modest masses.Comment: 12 Pages, Accepted for publication in A&

A beamforming approach to the self-calibration of phased arrays

In this paper, we propose a beamforming method for the calibration of the direction-independent gain of the analog chains of aperture arrays. The gain estimates are obtained by cross-correlating the output voltage of each antenna with a voltage beamformed using the other antennas of the array. When the beamforming weights are equal to the average cross-correlated power, a relation is drawn with the StEFCal algorithm. An example illustrates this approach for few point sources and a 256-element array

Digital Offset Calibration of an OPAMP Towards Improving Static Parameters of 90 nm CMOS DAC

In this paper, an on-chip self-calibrated 8-bit R-2R digital-to-analog converter (DAC) based on digitally compensated input offset of the operational amplifier (OPAMP) is presented. To improve the overall DAC performance, a digital offset cancellation method was used to compensate deviations in the input offset voltage of the OPAMP caused by process variations. The whole DAC as well as offset compensation circuitry were designed in a standard 90 nm CMOS process. The achieved results show that after the self-calibration process, the improvement of 48% in the value of DAC offset error is achieved

Camera distortion self-calibration using the plumb-line constraint and minimal Hough entropy

In this paper we present a simple and robust method for self-correction of camera distortion using single images of scenes which contain straight lines. Since the most common distortion can be modelled as radial distortion, we illustrate the method using the Harris radial distortion model, but the method is applicable to any distortion model. The method is based on transforming the edgels of the distorted image to a 1-D angular Hough space, and optimizing the distortion correction parameters which minimize the entropy of the corresponding normalized histogram. Properly corrected imagery will have fewer curved lines, and therefore less spread in Hough space. Since the method does not rely on any image structure beyond the existence of edgels sharing some common orientations and does not use edge fitting, it is applicable to a wide variety of image types. For instance, it can be applied equally well to images of texture with weak but dominant orientations, or images with strong vanishing points. Finally, the method is performed on both synthetic and real data revealing that it is particularly robust to noise.Comment: 9 pages, 5 figures Corrected errors in equation 1

Self calibration of photometric redshift scatter in weak lensing surveys

Photo-z errors, especially catastrophic errors, are a major uncertainty for precision weak lensing cosmology. We find that the shear-(galaxy number) density and density-density cross correlation measurements between photo-z bins, available from the same lensing surveys, contain valuable information for self-calibration of the scattering probabilities between the true-z and photo-z bins. The self-calibration technique we propose does not rely on cosmological priors nor parameterization of the photo-z probability distribution function, and preserves all of the cosmological information available from shear-shear measurement. We estimate the calibration accuracy through the Fisher matrix formalism. We find that, for advanced lensing surveys such as the planned stage IV surveys, the rate of photo-z outliers can be determined with statistical uncertainties of 0.01-1% for $z<2$ galaxies. Among the several sources of calibration error that we identify and investigate, the {\it galaxy distribution bias} is likely the most dominant systematic error, whereby photo-z outliers have different redshift distributions and/or bias than non-outliers from the same bin. This bias affects all photo-z calibration techniques based on correlation measurements. Galaxy bias variations of $O(0.1)$ produce biases in photo-z outlier rates similar to the statistical errors of our method, so this galaxy distribution bias may bias the reconstructed scatters at several-$\sigma$ level, but is unlikely to completely invalidate the self-calibration technique.Comment: v2: 19 pages, 10 figures. Added one figure. Expanded discussions. Accepted to MNRA