TY - JOUR
T1 - Study of resolution and super resolution in electromagnetic imaging for half-space problems
AU - Cui, Tie Jun
AU - Chew, Weng Cho
AU - Yin, Xiao Xing
AU - Hong, Wei
N1 - Funding Information:
Manuscript received January 2, 2003; revised July 15, 2003. This work was supported in part by the National Science Foundation of China for Distinguished Young Scholars under Grant 60225001, the U.S. Department of Energy (DOE) under Grant DOE DEFG07-97ER 14835, and in part by the National Science Foundation (NSF) under Grant NSF ECS 99-06651.
PY - 2004/6
Y1 - 2004/6
N2 - It has been observed that super resolution is possible in the electromagnetic imaging. In the first part of the paper, the possible resolution of image is investigated in the inversion of far-field data using the diffraction tomographic (DT) algorithm, where two cases are considered when the object is in a homogeneous space and in an air-earth half space. The study shows that the resolution of image for inversion of far-field data has been limited theoretically to 0.3536-0.5 wavelength using the DT algorithm in homogeneous-space problems, and it is even worse in half-space problems. If the transmitters and receivers are located in the near-field regime, however, the image resolution is less than 0.25 wavelength, which is the super-resolution phenomenon. In the second part of the paper, the physical reason for the super-resolution phenomenon is investigated using different electromagnetic inverse scattering methods. The study has demonstrated that the information of evanescent waves in the measurement data and its involvement in inversion algorithms is the main reason for the super resolution. Four inversion algorithms are considered for half-space problems: the DT algorithm, the spatial-domain Born approximation (BA), the Born iterative method (BIM), and the distorted BIM (DBIM). The first two belong to linear inverse scattering, while the last two belong to nonlinear inverse scattering. Further analysis shows that DBIM provides a better super resolution than BIM, and BIM provides a better super resolution than BA. Numerical simulations validate the above conclusions.
AB - It has been observed that super resolution is possible in the electromagnetic imaging. In the first part of the paper, the possible resolution of image is investigated in the inversion of far-field data using the diffraction tomographic (DT) algorithm, where two cases are considered when the object is in a homogeneous space and in an air-earth half space. The study shows that the resolution of image for inversion of far-field data has been limited theoretically to 0.3536-0.5 wavelength using the DT algorithm in homogeneous-space problems, and it is even worse in half-space problems. If the transmitters and receivers are located in the near-field regime, however, the image resolution is less than 0.25 wavelength, which is the super-resolution phenomenon. In the second part of the paper, the physical reason for the super-resolution phenomenon is investigated using different electromagnetic inverse scattering methods. The study has demonstrated that the information of evanescent waves in the measurement data and its involvement in inversion algorithms is the main reason for the super resolution. Four inversion algorithms are considered for half-space problems: the DT algorithm, the spatial-domain Born approximation (BA), the Born iterative method (BIM), and the distorted BIM (DBIM). The first two belong to linear inverse scattering, while the last two belong to nonlinear inverse scattering. Further analysis shows that DBIM provides a better super resolution than BIM, and BIM provides a better super resolution than BA. Numerical simulations validate the above conclusions.
KW - Far-field measurement
KW - Image resolution
KW - Linear inverse scattering
KW - Near-field measurement
KW - Nonlinear inverse scattering
KW - Super resolution
UR - http://www.scopus.com/inward/record.url?scp=2942741306&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=2942741306&partnerID=8YFLogxK
U2 - 10.1109/TAP.2004.829847
DO - 10.1109/TAP.2004.829847
M3 - Article
AN - SCOPUS:2942741306
VL - 52
SP - 1398
EP - 1411
JO - IEEE Transactions on Antennas and Propagation
JF - IEEE Transactions on Antennas and Propagation
SN - 0018-926X
IS - 6
ER -