scholarly journals Understanding the HERA Phase I receiver system with simulations and its impact on the detectability of the EoR delay power spectrum

2020 ◽  
Vol 500 (1) ◽  
pp. 1232-1242
Author(s):  
Nicolas Fagnoni ◽  
Eloy de Lera Acedo ◽  
David R DeBoer ◽  
Zara Abdurashidova ◽  
James E Aguirre ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Phase I ◽  
Electromagnetic Waves ◽  
Mutual Coupling ◽  
System Response ◽  
Receiver System ◽  
Simulated System ◽  
Systematic Effects ◽  
System Time ◽  
Large Sections

ABSTRACT The detection of the Epoch of Reionization (EoR) delay power spectrum using a ‘foreground avoidance method’ highly depends on the instrument chromaticity. The systematic effects induced by the radio telescope spread the foreground signal in the delay domain, which contaminates the EoR window theoretically observable. Applied to the Hydrogen Epoch of Reionization Array (HERA), this paper combines detailed electromagnetic and electrical simulations in order to model the chromatic effects of the instrument, and quantify its frequency and time responses. In particular, the effects of the analogue receiver, transmission cables, and mutual coupling are included. These simulations are able to accurately predict the intensity of the reflections occurring in the 150-m cable which links the antenna to the backend. They also show that electromagnetic waves can propagate from one dish to another one through large sections of the array due to mutual coupling. The simulated system time response is attenuated by a factor 104 after a characteristic delay which depends on the size of the array and on the antenna position. Ultimately, the system response is attenuated by a factor 105 after 1400 ns because of the reflections in the cable, which corresponds to characterizable k∥-modes above 0.7 $h\,\,\rm {Mpc}^{-1}$ at 150 MHz. Thus, this new study shows that the detection of the EoR signal with HERA Phase I will be more challenging than expected. On the other hand, it improves our understanding of the telescope, which is essential to mitigate the instrument chromaticity.

scholarly journals Clustering properties of TGSS radio sources

2019 ◽  
Vol 623 ◽  
pp. A148 ◽  
Author(s):  
Arianna Dolfi ◽  
Enzo Branchini ◽  
Maciej Bilicki ◽  
Andrés Balaguera-Antolínez ◽  
Isabella Prandoni ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Angular Spectrum ◽  
Radio Sources ◽  
Angular Power Spectrum ◽  
Sky Survey ◽  
Systematic Effects ◽  
Angular Correlation Function ◽  
Multiple Component ◽  
Anomalous Nature

We investigate the clustering properties of radio sources in the Alternative Data Release 1 of the TIFR GMRT Sky Survey (TGSS), focusing on large angular scales, where previous analyses have detected a large clustering signal. After appropriate data selection, the TGSS sample we use contains ∼110 000 sources selected at 150 MHz over ∼70% of the sky. The survey footprint is largely superimposed on that of the NRAO VLA Sky Survey (NVSS) with the majority of TGSS sources having a counterpart in the NVSS sample. These characteristics make TGSS suitable for large-scale clustering analyses and facilitate the comparison with the results of previous studies. In this analysis we focus on the angular power spectrum, although the angular correlation function is also computed to quantify the contribution of multiple-component radio sources. We find that on large angular scales, corresponding to multipoles 2 ≤ ℓ ≤ 30, the amplitude of the TGSS angular power spectrum is significantly larger than that of the NVSS. We do not identify any observational systematic effects that may explain this mismatch. We have produced a number of physically motivated models for the TGSS angular power spectrum and found that all of them fail to match observations, even when taking into account observational and theoretical uncertainties. The same models provide a good fit to the angular spectrum of the NVSS sources. These results confirm the anomalous nature of the TGSS large-scale power, which has no obvious physical origin and seems to indicate that unknown systematic errors are present in the TGSS dataset.

scholarly journals Optimal strategy for polarization modulation in the LSPE-SWIPE experiment

2018 ◽  
Vol 609 ◽  
pp. A52 ◽  
Author(s):  
A. Buzzelli ◽  
P. de Bernardis ◽  
S. Masi ◽  
N. Vittorio ◽  
G. de Gasperis
Keyword(s):  
Power Spectrum ◽  
Polarization Modulation ◽  
Microwave Background ◽  
Angular Power Spectrum ◽  
Half Wave ◽  
Wide Range ◽  
Cmb Polarization ◽  
Systematic Effects ◽  
Single Detector ◽  
Frequency Map

Context. Cosmic microwave background (CMB) B-mode experiments are required to control systematic effects with an unprecedented level of accuracy. Polarization modulation by a half wave plate (HWP) is a powerful technique able to mitigate a large number of the instrumental systematics. Aims. Our goal is to optimize the polarization modulation strategy of the upcoming LSPE-SWIPE balloon-borne experiment, devoted to the accurate measurement of CMB polarization at large angular scales. Methods. We departed from the nominal LSPE-SWIPE modulation strategy (HWP stepped every 60 s with a telescope scanning at around 12 deg/s) and performed a thorough investigation of a wide range of possible HWP schemes (either in stepped or continuously spinning mode and at different azimuth telescope scan-speeds) in the frequency, map and angular power spectrum domain. In addition, we probed the effect of high-pass and band-pass filters of the data stream and explored the HWP response in the minimal case of one detector for one operation day (critical for the single-detector calibration process). We finally tested the modulation performance against typical HWP-induced systematics. Results. Our analysis shows that some stepped HWP schemes, either slowly rotating or combined with slow telescope modulations, represent poor choices. Moreover, our results point out that the nominal configuration may not be the most convenient choice. While a large class of spinning designs provides comparable results in terms of pixel angle coverage, map-making residuals and BB power spectrum standard deviations with respect to the nominal strategy, we find that some specific configurations (e.g., a rapidly spinning HWP with a slow gondola modulation) allow a more efficient polarization recovery in more general real-case situations. Conclusions. Although our simulations are specific to the LSPE-SWIPE mission, the general outcomes of our analysis can be easily generalized to other CMB polarization experiments.

Statistical determination of geophysical well log response functions

Geophysics ◽  
1983 ◽  
Vol 48 (11) ◽  
pp. 1525-1535 ◽  
Author(s):  
Eugene A. Nosal
Keyword(s):  
Power Spectrum ◽  
Response Function ◽  
System Response ◽  
General Terms ◽  
Induction Logging ◽  
Conductivity Profile ◽  
Statistical Determination ◽  
The One

The vertical response function of induction logging tools is shown to be derivable from a power spectrum analysis of the measurement. The vertical response function is the one‐dimensional sequence of weights that characterizes how the tool combines the rock conductivities along the borehole to form an output called the apparent conductivity; it is the system impulse response. The value of knowing this function lies in the possible use of filter theory to aid in data processing and interpretation. Two general notions establish the framework for the analysis. The first is that logging is a linear, convolutional operation. Second, the earth’s conductivity profile forms a stochastic process. The probabilistic component is fleshed out by reasonably based assumptions about the occurrence of bed boundaries and nature of conductivity changes across them. Brought together, these tenets create a characterization of the conductivity sequence that is not a stationary process, but rather is intrinsic, as defined in the discipline of geostatistics. Such a process is described by a variogram, and it is increments of the process that are stationary. The connection between the power spectrum of the measurement and the system response function is made when the convolutional model is merged with the conductivity process. Some examples of induction log functions are shown using these ideas. The analysis is presented in general terms for possibly wider application.

Collisionless damping of ordinary electromagnetic waves in the ionospheric plasma with power spectrum of inhomogeneities

1991 ◽  
Vol 34 (3) ◽  
pp. 214-220
Author(s):  
A. G. Bronin ◽  
P. F. Denisenko ◽  
G. A. Zhbankov ◽  
N. A. Zabotin
Keyword(s):  
Power Spectrum ◽  
Electromagnetic Waves ◽  
Ionospheric Plasma

scholarly journals Modeling of the tensometric measuring system

2019 ◽  
pp. 18-23
Author(s):  
Jozef Novotnak ◽  
Miroslav Smelko ◽  
Rudolf Andoga ◽  
Pavol Lipovsky ◽  
Martin Filko
Keyword(s):  
Step Change ◽  
Measuring System ◽  
System Response ◽  
Graphical Comparison ◽  
Simulated System ◽  
Measured System ◽  
System Characteristics

Article deals with the design of a model of a tensometric measuring system. Authors in this article describes the procedure for measuring the system response to a step change in load and then the procedure creating a model. The article shows a graphical comparison between the measured ones system characteristics and simulated system characteristics. The conclusion is given calculated errors between measured system characteristics and simulated system characteristics.

Analysis of Plasmonic Structures by Spectroscopic Ellipsometry

2016 ◽  
pp. 208-239
Author(s):  
Jose Luis Pau ◽  
Antonio García Marín ◽  
María Jesús Hernández ◽  
Manuel Cervera ◽  
Juan Piqueras
Keyword(s):  
Thin Films ◽  
Spectroscopic Ellipsometry ◽  
Electromagnetic Waves ◽  
Near Infrared ◽  
Electromagnetic Spectrum ◽  
Surface Polaritons ◽  
Metal Thin Films ◽  
Plasmonic Structures ◽  
Large Sections ◽  
Total Internal Reflection Ellipsometry

This chapter focuses on the plasmonic effects that appear in the ellipsometric functions and the pseudodielectric function when metal thin films and nanoparticles are analyzed by spectroscopic ellipsometry in the visible, near infrared and ultraviolet regions of the electromagnetic spectrum. The chapter is structured in two large sections. The first section reviews the basics of total internal reflection ellipsometry (TIRE), based on the excitation of surface polaritons in metal thin films. The conditions required to excite polaritons in TIRE systems are analyzed along with the main characteristics of those electromagnetic waves. The second section of the chapter is devoted to study the optical properties of plasmonic resonances in nanostructures and the characteristics introduced in the dielectric functions. The treatment of optical anisotropies and Fano resonances in the ellipsometric models is discussed. The last section of the chapter reviews the state of the art of the technique in biosensing applications.

scholarly journals Self-calibration of weak lensing systematic effects using combined two- and three-point statistics

2021 ◽  
Author(s):  
Susan Pyne ◽  
Benjamin Joachimi
Keyword(s):  
Power Spectrum ◽  
Energy Equation ◽  
Cosmological Parameters ◽  
Weak Lensing ◽  
Calibration Data ◽  
Joint Power ◽  
Systematic Uncertainties ◽  
Systematic Effects ◽  
Two Parameters ◽  
Baseline Approach

Abstract We investigate the prospects for using the weak lensing bispectrum alongside the power spectrum to control systematic uncertainties in a Euclid-like survey. Three systematic effects are considered: the intrinsic alignment of galaxies, uncertainties in the means of tomographic redshift distributions, and multiplicative bias in the measurement of the shear signal. We find that the bispectrum is very effective in mitigating these systematic errors. Varying all three systematics simultaneously, a joint power spectrum and bispectrum analysis reduces the area of credible regions for the cosmological parameters Ωm and σ8 by a factor of 90 and for the two parameters of a time-varying dark energy equation of state by a factor of almost 20, compared with the baseline approach of using the power spectrum alone and of imposing priors consistent with the accuracy requirements specified for Euclid. We also demonstrate that including the bispectrum self-calibrates all three systematic effects to the stringent levels required by the forthcoming generation of weak lensing surveys, thereby reducing the need for external calibration data.

scholarly journals SOFT COMPUTING AS A SOLUTION TO TIME/COST DISTRIBUTOR

2014 ◽  
pp. 100-105
Author(s):  
Nabil M. Hewahi
Keyword(s):  
Fuzzy Logic ◽  
Soft Computing ◽  
Main Idea ◽  
System Response ◽  
Time Cost ◽  
Importance Value ◽  
Time Limits ◽  
Lower Priority ◽  
Second Stage ◽  
System Time

In this paper we present a theoretical model based on soft computing to distribute the time/cost among the industry/machine sensors or effectors based on the type of the application. One of the most unstudied significant work is to recognize which sensor in an industry for example has higher priority than others. This is important to know which sensor to be checked first and within time limits of the system response. The problem of such systems is their variant environmental situations. Based on these varied situations, the priority of the importance of each sensor might change from time to another. Due to this uncertainty and lack of some information, soft computing is considered to be one of the plausible solutions. The presented idea is based on initially training of the system and continuously exploiting the system experience of the degree of importance of the sensors. The proposed system has three main stages, the first stage is concerned with training the system to obtain the necessary system time to respond, the necessary time allocated to recognize which sensors to check (or which has higher priority), and the initial importance value for each sensor, which indicates the initial judgment about the sensor importance. The second stage is to use the system experience about the importance of the sensor using fuzzy logic to decide the final values of each sensor 's importance. Based on the output of the second stage and the output of the first stage, the system distributes the time/cost among the sensors (some sensors with lower priority might be neglected). The main idea of the proposed work is based on neurofuzzy.

scholarly journals A High-Resolution Foreground Model for the MWA EoR1 Field: Model and Implications for EoR Power Spectrum Analysis

2017 ◽  
Vol 34 ◽  
Author(s):  
P. Procopio ◽  
R. B. Wayth ◽  
J. Line ◽  
C. M. Trott ◽  
H. T. Intema ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Field Model ◽  
Single Point ◽  
Neutral Hydrogen ◽  
Point Sources ◽  
Systematic Effects ◽  
Calibration Accuracy ◽  
Compact Sources ◽  
Residual Power

AbstractThe current generation of experiments aiming to detect the neutral hydrogen signal from the Epoch of Reionisation (EoR) is likely to be limited by systematic effects associated with removing foreground sources from target fields. In this paper, we develop a model for the compact foreground sources in one of the target fields of the MWA’s EoR key science experiment: the ‘EoR1’ field. The model is based on both the MWA’s GLEAM survey and GMRT 150 MHz data from the TGSS survey, the latter providing higher angular resolution and better astrometric accuracy for compact sources than is available from the MWA alone. The model contains 5 049 sources, some of which have complicated morphology in MWA data, Fornax A being the most complex. The higher resolution data show that 13% of sources that appear point-like to the MWA have complicated morphology such as double and quad structure, with a typical separation of 33 arcsec. We derive an analytic expression for the error introduced into the EoR two-dimensional power spectrum due to peeling close double sources as single point sources and show that for the measured source properties, the error in the power spectrum is confined to highk⊥modes that do not affect the overall result for the large-scale cosmological signal of interest. The brightest 10 mis-modelled sources in the field contribute 90% of the power bias in the data, suggesting that it is most critical to improve the models of the brightest sources. With this hybrid model, we reprocess data from the EoR1 field and show a maximum of 8% improved calibration accuracy and a factor of two reduction in residual power ink-space from peeling these sources. Implications for future EoR experiments including the SKA are discussed in relation to the improvements obtained.

scholarly journals Damping Coefficient Induces Stochastic Multiresonance in Bistable System with Asymmetric Dichotomous Noise

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
Juan Wu ◽  
Yong Xu
Keyword(s):  
Power Spectrum ◽  
Damping Coefficient ◽  
Bistable System ◽  
System Response ◽  
Asymmetric Distribution ◽  
Potential Wells ◽  
Dichotomous Noise ◽  
System Parameters ◽  
Asymmetric Dichotomous Noise ◽  
Averaged Power Spectrum

Stochastic resonance (SR) and stochastic multiresonance (SMR) phenomena as a function of the underdamping and overdamping coefficients in bistable system with asymmetric dichotomous noise are investigated numerically. By the efficient numerical simulation of the asymmetric dichotomous noise and the fourth-order Runge-Kutta algorithm, we calculate the system responses, the averaged power spectrum, and the signal-noise-ratio (SNR) that can be a measure of the existence of SR and SMR phenomenon. And the effects of damping coefficients on the three characteristics are analyzed. Firstly, it is found that the periodic asymmetric distribution of the particle’s hopping between two potential wells in the system response is gradually weakened as underdamping coefficient is increased to overdamping coefficient. And it also displays the periodic asymmetric distribution under the circumstance of overdamping coefficient. Then the averaged power spectrum exhibits multiple sharp peaks, and the highest peak increases and decreases for underdamping coefficient which is added to overdamping coefficient. Finally, SNR versus the damping coefficient for the system parameters and the noise parameters are acquired and they show multiple peaks and valleys, which illustrates the obvious SMR phenomena in bistable system with asymmetric dichotomous noise.

Sign in / Sign up

Export Citation Format

Share Document