Far-field performance of linear antennas determined from near-field data

2002 ◽  
Vol 50 (3) ◽  
pp. 408-410 ◽  
Author(s):  
F. Las-Heras ◽  
B. Galocha ◽  
J.L. Besada
Keyword(s):  
Field Data ◽  
Near Field ◽  
Field Performance ◽  
Far Field

Far-field pattern reconstruction directly from a minimum number of helicoidal near-field data

2012 ◽  
Author(s):  
Francesco D'Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
Massimo Migliozzi
Keyword(s):  
Field Data ◽  
Near Field ◽  
Field Pattern ◽  
Far Field ◽  
Minimum Number ◽  
Pattern Reconstruction ◽  
Far Field Pattern

scholarly journals Near-field imaging with far-field data

2016 ◽  
Vol 60 ◽  
pp. 36-42 ◽  
Author(s):  
Gang Bao ◽  
Peijun Li ◽  
Yuliang Wang
Keyword(s):  
Field Data ◽  
Near Field ◽  
Far Field ◽  
Near Field Imaging ◽  
Field Imaging

Inversion of controlled source audio‐frequency magnetotellurics data for a horizontally layered earth

Geophysics ◽  
1999 ◽  
Vol 64 (6) ◽  
pp. 1689-1697 ◽  
Author(s):  
Partha S. Routh ◽  
Douglas W. Oldenburg
Keyword(s):  
Field Data ◽  
Near Field ◽  
Dipole Source ◽  
Earth Model ◽  
Far Field ◽  
Audio Frequency ◽  
Controlled Source ◽  
The Earth ◽  
Data Points ◽  
Corrected Data

We present a technique for inverting controlled source audio‐frequency magnetotelluric (CSAMT) data to recover a 1-D conductivity structure. The earth is modeled as a set of horizontal layers with constant conductivity, and the data are apparent resistivities and phases computed from orthogonal electric and magnetic fields due to a finite dipole source. The earth model has many layers compared to the number of data points, and therefore the solution is nonunique. Among the possible solutions, we seek a model with desired character by minimizing a particular model objective function. Traditionally, CSAMT data are inverted either by using the far‐field data where magnetotelluric (MT) equations are valid or by correcting the near‐field data to an equivalent plane‐wave approximation. Here, we invert both apparent resistivity and phase data from the near‐field transition zone and the far‐field regions in the full CSAMT inversion without any correction. Our inversion is compared with that obtained by inverting near‐field corrected data using an MT algorithm. Both synthetic and field data examples indicate that a full CSAMT inversion provides improved information about subsurface conductivity.

scholarly journals An Innovative Direct NF-FF Transformation Technique with Helicoidal Scanning

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Francesco D’Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
Massimo Migliozzi
Keyword(s):  
Electromagnetic Fields ◽  
Field Data ◽  
Near Field ◽  
Transverse Dimension ◽  
Computational Effort ◽  
Far Field ◽  
Transformation Technique ◽  
Spherical Antenna ◽  
Field Transformation ◽  
Mechanical Scanning

A direct near-field-far-field transformation with helicoidal scanning is developed. It is based on the nonredundant sampling representation of electromagnetic fields and uses a spherical antenna modelling to determine the number of helix turns. Moreover, the number of voltage samples on each of them is fixed by the maximum transverse dimension of the antenna, both to simplify the mechanical scanning and to reduce the computational effort. This technique allows the evaluation of the antenna far field directly from a minimum set of near-field data without interpolating them. Although the number of near-field data employed by the developed technique is slightly increased with respect to that required by rigorously applying the nonredundant sampling representation on the helix, it is still remarkably smaller than that needed by the standard near-field-far-field transformation with cylindrical scanning. The effectiveness of the technique is assessed by numerical and experimental results.

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