scholarly journals Direction of Arrival Estimation Using Two Hydrophones: Frequency Diversity Technique for Passive Sonar

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 2001 ◽  
Author(s):  
Peng Li ◽  
Xinhua Zhang ◽  
Wenlong Zhang
Keyword(s):  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
Estimation Algorithm ◽  
Time Delay Estimation ◽  
High Signal ◽  
Frequency Diversity ◽  
Spectral Density Matrix ◽  
Processing Gain ◽  
The Cross ◽  
Diversity Technique

The traditional passive azimuth estimation algorithm using two hydrophones, such as cross-correlation time-delay estimation and cross-spectral phase estimation, requires a high signal-to-noise ratio (SNR) to ensure the clarity of the estimated target trajectory. This paper proposes an algorithm to apply the frequency diversity technique to passive azimuth estimation. The algorithm also uses two hydrophones but can obtain clear trajectories at a lower SNR. Firstly, the initial phase of the signal at different frequencies is removed by calculating the cross-spectral density matrix. Then, phase information between frequencies is used for beamforming. In this way, the frequency dimension information is used to improve the signal processing gain. This paper theoretically analyzes the resolution and processing gain of the algorithm. The simulation results show that the proposed algorithm can estimate the target azimuth robustly under the conditions of a single target (SNR = −16 dB) and multiple targets (SNR = −10 dB), while the cross-correlation algorithm cannot. Finally, the algorithm is tested by the swell96 data and the South Sea experimental data. When dealing with rich frequency signals, the performance of the algorithm using two hydrophones is even better than that of the conventional broadband beamforming of the 64-element array. This further validates the effectiveness and advantages of the algorithm.

scholarly journals Multiple stellar systems

1986 ◽  
Vol 118 ◽  
pp. 441-442
Author(s):  
A. Duquennoy ◽  
M. Mayor
Keyword(s):  
Radial Velocity ◽  
Small Amplitude ◽  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Correlation Technique ◽  
Multiple Systems ◽  
Triple Systems ◽  
The Cross

A spectroscopic survey of visual binaries with known orbital elements has been carried out with the radial velocity scanner CORAVEL at the Haute-Provence Observatory, since 1977, (Baranne, Mayor, Poncet, 1979). This survey of more than 100 visual systems, selected from Dommanget's catalogue (1967) (see also a new edition 1982) was first devoted to the determination of stellar masses. Several multiple systems were detected and have permitted also a study of the structure of triple systems. We have detected and measured in particular a class of triple systems with radial velocity variations of small amplitude. Taking advantage of the high resolution and high signal-to-noise ratio accessible with the cross-correlation technique, such small amplitude radial velocity curves are sometimes derived only through the change of width and shape of the cross-correlation function. Let us recall that the cc-function of a SB2 (or SB3) system is only the weighted sum of the individual cc-functions (Mayor, 1985). This property of the cross-correlation combined with the linearity of the detector allow a very simple analysis of blended dips. The full width at half depth of the cross-correlation dip is about FWHD = 16 km/s (in absence of noticeable rotation). Analysis of blended systems allows a good determination of the two individual velocities if the difference |vr1 -Vr2| is equal or larger than about 0.15 *FWHD (about 2 km/s).

Time Delay Estimator for Boiler Tube Leakage Localization

2011 ◽  
Author(s):  
Liansuo An ◽  
Peng Wang ◽  
Guoqing Shen ◽  
Jie Shi
Keyword(s):  
Time Delay ◽  
Background Noise ◽  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
Estimation Algorithm ◽  
Time Delay Estimation ◽  
Boiler Tube ◽  
Boiler Furnace ◽  
Direct Energy ◽  
Leakage Location

The inference of strong background noise and reflected by the wall and tube rows surface makes it impossible that justify accurately leakage position employing the characteristic received by multi-channel sensors. It is the ‘bottleneck’ for promoting the accuracy of boiler tube leakage location. The 600MW supercritical boiler model was established, the leakage source propagation process of reflection and attenuation in boiler furnace was simulated by EASE. The approximate signal to noise ratio (SNR) was obtained and the reverberation time was calculated with the squared impulse response integration method on the foundation of simulation. The time delay estimation algorithm PTN, SWITCH derived from PHAT and ML, respectively, are proposed and experiments results revealed the superiority over the classical generalized cross correlation (GCC) method in reverberant and noisy boiler background. Although SWITCH is outperformed by PTN slightly, but the prior knowledge of reverberant energy to direct energy ratio may be hard to obtain in practice and frequencies onset detection is required in PTN method, so the implementation of SWITCH is much easier.

scholarly journals Testing general relativity with the Doppler magnification effect

2019 ◽  
Vol 488 (3) ◽  
pp. 3759-3771 ◽  
Author(s):  
Sambatra Andrianomena ◽  
Camille Bonvin ◽  
David Bacon ◽  
Philip Bull ◽  
Chris Clarkson ◽  
...  
Keyword(s):  
General Relativity ◽  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
Density Fluctuations ◽  
Signal To Noise ◽  
Tests Of General Relativity ◽  
Velocity Statistics ◽  
The Cross ◽  
Noise Ratio ◽  
Magnification Effect

ABSTRACT The apparent sizes and brightnesses of galaxies are correlated in a dipolar pattern around matter overdensities in redshift space, appearing larger on their near side and smaller on their far side. The opposite effect occurs for galaxies around an underdense region. These patterns of apparent magnification induce dipole and higher multipole terms in the cross-correlation of galaxy number density fluctuations with galaxy size/brightness (which is sensitive to the convergence field). This provides a means of directly measuring peculiar velocity statistics at low and intermediate redshift, with several advantages for performing cosmological tests of general relativity (GR). In particular, it does not depend on empirically calibrated scaling relations like the Tully–Fisher and Fundamental Plane methods. We show that the next generation of spectroscopic galaxy redshift surveys will be able to measure the Doppler magnification effect with sufficient signal-to-noise ratio to test GR on large scales. We illustrate this with forecasts for the constraints that can be achieved on parametrized deviations from GR for forthcoming low-redshift galaxy surveys with DESI and SKA2. Although the cross-correlation statistic considered has a lower signal-to-noise ratio than RSD, it will be a useful probe of GR since it is sensitive to different systematics.

The Algorithm of Acoustic Location for Boiler Tube Leakage

2010 ◽  
Vol 97-101 ◽  
pp. 3024-3027
Author(s):  
Peng Tong ◽  
Lian Suo An ◽  
Gen Shan Jiang ◽  
Yu Qing Wang
Keyword(s):  
Time Delay ◽  
Cross Correlation ◽  
Accurate Result ◽  
Correlation Method ◽  
Estimation Algorithm ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Value Of Time ◽  
Noise Power ◽  
Boiler Tube

The time delay estimation algorithm based on generalized cross correlation, can suppress the noise power effectively. More accurate result can be gotten by this method of time delay estimation. It is proved by simulation and experimentation that the estimated value of time delay given by generalized cross correlation method is more accurate than which is given by basic correlation method when the signal and noise ratio is stationary, thus the location result based on the time delay is more accurate.

scholarly journals Li abundances and chromospheric activity of BY Dra type stars

2009 ◽  
Vol 5 (S268) ◽  
pp. 343-344
Author(s):  
Tamara V. Mishenina ◽  
Caroline Soubiran ◽  
Valery V. Kovtyukh ◽  
Stanislav I. Belik
Keyword(s):  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
Large Fraction ◽  
Ratio Method ◽  
Clear Correlation ◽  
High Signal ◽  
Echelle Spectrograph ◽  
Active Stars ◽  
Ionization Balance ◽  
Line Depth

AbstractAtmospheric parameters and Li abundances have been determined for 162 stars observed at high resolution, high signal to noise ratio with the ELODIE echelle spectrograph (OHP, France). Among them, about 70 stars are active stars with a large fraction of BY Dra type stars. For all stars, rotational velocities were obtained with a calibration of the cross-correlation function, effective temperatures by the line depth ratio method, surface gravities by the parallaxe method and by the ionization balance of iron. The frequency of stars with observed lithium is significantly higher in active stars than in non active stars. Among active stars, no clear correlation has been found between different indicators of activity for our sample stars, but some correlation of an index R′H K and vsini is observed.

A Fast and Efficient Time-Delay Estimation Algorithm for Sound Localization

2011 ◽  
Vol 474-476 ◽  
pp. 1201-1204 ◽  
Author(s):  
Guan Qun Liu ◽  
Ru Bo Zhang ◽  
Dong Xu
Keyword(s):  
Time Delay ◽  
Sound Localization ◽  
Cross Correlation ◽  
Estimation Algorithm ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Important Research ◽  
Memory Space ◽  
Important Research Topic ◽  
Original Time

Time-delay estimation is an important research topic of sound localization. According to the specificity of time-delay in sound localization, a fast and efficient time-delay estimation algorithm is proposed based on the principle of fast linear cross correlation. Relative to the original time-delay estimation algorithm based on fast linear cross correlation, the proposed algorithm has enormous advantages in the time complexity and space complexity. The computing speed is twice faster than the original time-delay estimation algorithm, while the size of the memory space used is half of the original time-delay estimation algorithm.

scholarly journals Time Delay Estimation Method Used Median Filter in Low Signal to Noise Ratio Pulse Environment

2021 ◽  
Vol 252 ◽  
pp. 02039
Author(s):  
Hang Liu ◽  
Wenhong Liu
Keyword(s):  
Signal Processing ◽  
Time Delay ◽  
Signal To Noise Ratio ◽  
Median Filter ◽  
Estimation Algorithm ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
P Value ◽  
Signal To Noise ◽  
Second Order Statistics

In practice, the collected signal often contains impulsive noise. The classical time delay estimation algorithm based on the second-order statistics of Gaussian distribution will degrade or even be unreliable, so that it cannot be used. Although the fractional low-order signal processing method can be better adapted to signal processing in the impulse noise environment, the determination of the order p value of the fractional low-order moment depends on the prior knowledge or estimation of the characteristic index α value of the pulse, and when the pulse is stronger or the signal-to-noise ratio is low, the performance cannot meet the requirements well. The paper adopted the method of median filter preprocessing. First, the abnormal points (pulse points) are removed in the noise and return the noise to the Gaussian model distribution; next, use the time delay estimation algorithm under the second-order statistics to avoid the estimate of p-value. Computer simulation experiments show that the method proposed in this paper has better estimation performance in low snr pulse environment.

scholarly journals Cross-Correlation and Joint Spectro-Temporal Receptive Field Properties in Auditory Cortex

2005 ◽  
Vol 93 (1) ◽  
pp. 378-392 ◽  
Author(s):  
Masahiko Tomita ◽  
Jos J. Eggermont
Keyword(s):  
Auditory Cortex ◽  
Neural Activity ◽  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
Receptive Fields ◽  
Primary Auditory Cortex ◽  
Network Activity ◽  
Electrode Arrays ◽  
The Cross ◽  
The Right

Recordings were made from the right primary auditory cortex in 17 adult cats using two eight-electrode arrays. We recorded the neural activity under spontaneous firing conditions and during random, multi-frequency stimulation, at 65 dB SPL, from the same units. Multiple single-unit (MSU) recordings (281) were stationary through 900 s of silence and during 900 s of stimulation. The cross-correlograms of 545 MSU pairs with peak lag times within 10 ms from zero lag time were analyzed. Stimulation reduced the correlation in background activity, and as a result, the signal-to-noise ratio of correlated activity in response to the stimulus was enhanced. Reconstructed spectro-temporal receptive fields (STRFs) for coincident spikes showed larger STRF overlaps, suggesting that coincident neural activity serves to sharpen the resolution in the spectro-temporal domain. The cross-correlation for spikes contributing to the STRF depended much stronger on the STRF overlap than the cross-correlation during either silence or for spikes that did not contribute to the STRF (OUT-STRF). Compared with that for firings during silence, the cross-correlation for the OUT-STRF spikes was much reduced despite the unchanged firing rate. This suggests that stimulation breaks up the large neural assembly that exists during long periods of silence into a stimulus related one and maybe several others. As a result, the OUT-STRF spikes of the unit pairs, now likely distributed across several assemblies, are less correlated than during long periods of silence. Thus the ongoing network activity is significantly different from that during stimulation and changes afterng arousal during stimulation.

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