SPACE-TIME MATRIX METHOD FOR MIXED NEAR-FIELD AND FAR-FIELD SOURCES LOCALIZATION

2014 ◽  
Vol 36 ◽  
pp. 131-137 ◽  
Author(s):  
Ruiyan Du ◽  
Fulai Liu ◽  
Jinkuan Wang
Keyword(s):  
Matrix Method ◽  
Near Field ◽  
Space Time ◽  
Far Field

scholarly journals Some Analytic Results for the Study of Broadband Noise Radiation from Wings, Propellers and Jets in Uniform Motion

2003 ◽  
Vol 2 (3) ◽  
pp. 335-350 ◽  
Author(s):  
F. Farassat ◽  
J. Casper
Keyword(s):  
Correlation Function ◽  
Reference Frame ◽  
Cross Correlation ◽  
Near Field ◽  
Space Time ◽  
Broadband Noise ◽  
Uniform Motion ◽  
Far Field ◽  
Forward Motion ◽  
Radiated Noise

Alan Powell has made significant contributions to the understanding of many aeroacoustic problems, in particular, the problems of broadband noise from jets and boundary layers. In this paper, some analytic results are presented for the calculation of the correlation function of the broadband noise radiated from a wing, a propeller, and a jet in uniform forward motion. It is shown that, when the observer (or microphone) motion is suitably chosen, the geometric terms of the radiation formula become time independent. The time independence of these terms leads to a significant simplification of the statistical analysis of the radiated noise, even when the near field terms are included. For a wing in forward motion, if the observer is in the moving reference frame, then the correlation function of the near and far field noise can be related to a space-time cross-correlation function of the pressure on the wing surface. A similar result holds for a propeller in forward flight if the observer is in a reference frame that is attached to the propeller and rotates at the shaft speed. For a jet in motion, it is shown that the correlation function of the radiated noise can be related to the space-time cross-correlation of the Lighthill stress tensor in the jet. Exact analytical results are derived for all three cases. For the cases under present consideration, the inclusion of the near field terms does not introduce additional complexity, as compared to existing formulations that are limited to the far field.

Numerical relativity - III. The Bondi mass revisited

1989 ◽  
Vol 424 (1866) ◽  
pp. 211-222 ◽  
Keyword(s):  
Mass Flux ◽  
Numerical Relativity ◽  
Near Field ◽  
Space Time ◽  
Far Field ◽  
Null Tetrad ◽  
Related Space ◽  
Bondi Mass ◽  
Numerical Tool

Expressions for the Bondi mass and mass flux far from an isolated system are derived by using an arbitrary Newman–Penrose null tetrad in the conformally related space-time. A numerical tool for relating the near field of an isolated gravitationally radiating system to the far field is developed, so that the mass of such a system can be computed and some simple examples are described.

scholarly journals Joint Space and Time Processing for Unknown Mutual Coupling Blind Calibration and Mixed Sources Identification Using Uniform Circular Array

Electronics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 525 ◽  
Author(s):  
Kai Wang ◽  
Ling Wang ◽  
Jian Xie ◽  
Yuexian Wang ◽  
Zhanolin Zhang
Keyword(s):  
Mutual Coupling ◽  
Near Field ◽  
Joint Space ◽  
Space Time ◽  
Far Field ◽  
Circular Array ◽  
Rank Reduction ◽  
Time Processing ◽  
Sources Identification ◽  
Blind Calibration

In classification and localization of mixed far-field and near-field sources, the unknown mutual coupling degrades the performance of most high-resolution algorithms. In practice, the assumption of an ideal receiving sensor array is rarely satisfied. This paper proposes an effective algorithm of mixed sources identification using uniform circular array under unknown mutual coupling. Firstly, according to rank reduction and joint space–time processing, the directions of arrival of far-field sources is estimated directly without mutual coupling elimination. Addition, the joint space–time processing can improve the estimation results in the case of low signal noise ratio of incoming signal sources and small number of snapshots. Then, these estimates are adopted to reconstruct the mutual coupling matrix. Finally, both direction and range parameters of near-field sources are obtained through spatial search after mutual coupling effects and far-field components elimination. The proposed algorithm is described in detail, and its behavior is illustrated by numerical examples.

Magnetic Tag Antenna for UHF Near-field and Far-Field RFID Applications

2015 ◽  
Vol 5 (2) ◽  
pp. 119
Author(s):  
Mondher Dhaouadi ◽  
M. Mabrouk ◽  
T. Vuong ◽  
A. Ghazel
Keyword(s):  
Near Field ◽  
Far Field ◽  
Rfid Applications
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