scholarly journals Surface Wave Multipath Signals in Near-Field Microwave Imaging

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Paul M. Meaney ◽  
Fridon Shubitidze ◽  
Margaret W. Fanning ◽  
Maciej Kmiec ◽  
Neil R. Epstein ◽  
...  
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Antenna Arrays ◽  
Imaging Techniques ◽  
Near Field ◽  
Microwave Imaging ◽  
Feed Line ◽  
Receiving Antenna ◽  
Wave Effects ◽  
Multipath Signals

Microwave imaging techniques are prone to signal corruption from unwanted multipath signals. Near-field systems are especially vulnerable because signals can scatter and reflect from structural objects within or on the boundary of the imaging zone. These issues are further exacerbated when surface waves are generated with the potential of propagating along the transmitting and receiving antenna feed lines and other low-loss paths. In this paper, we analyze the contributions of multi-path signals arising from surface wave effects. Specifically, experiments were conducted with a near-field microwave imaging array positioned at variable heights from the floor of a coupling fluid tank. Antenna arrays with different feed line lengths in the fluid were also evaluated. The results show that surface waves corrupt the received signals over the longest transmission distances across the measurement array. However, the surface wave effects can be eliminated provided the feed line lengths are sufficiently long independently of the distance of the transmitting/receiving antenna tips from the imaging tank floor. Theoretical predictions confirm the experimental observations.

scholarly journals Fast, Robust, and Low-Cost Microwave Imaging of Multiple Non-Metallic Pipes

Electronics ◽  
2021 ◽  
Vol 10 (15) ◽  
pp. 1762
Author(s):  
Yuki Gao ◽  
Maryam Ravan ◽  
Reza K. Amineh
Keyword(s):  
Antenna Arrays ◽  
Oil And Gas ◽  
Imaging System ◽  
Imaging Techniques ◽  
Low Cost ◽  
Microwave Imaging ◽  
Airport Security ◽  
Destructive Testing ◽  
Security Screening ◽  
Industrial Sectors

The use of non-metallic pipes and composite components that are low-cost, durable, light-weight, and resilient to corrosion is growing rapidly in various industrial sectors such as oil and gas industries in the form of non-metallic composite pipes. While these components are still prone to damages, traditional non-destructive testing (NDT) techniques such as eddy current technique and magnetic flux leakage technique cannot be utilized for inspection of these components. Microwave imaging can fill this gap as a favorable technique to perform inspection of non-metallic pipes. Holographic microwave imaging techniques are fast and robust and have been successfully employed in applications such as airport security screening and underground imaging. Here, we extend the use of holographic microwave imaging to inspection of multiple concentric pipes. To increase the speed of data acquisition, we utilize antenna arrays along the azimuthal direction in a cylindrical setup. A parametric study and demonstration of the performance of the proposed imaging system will be provided.

scholarly journals Surface Wave Effects on the Wind-Power Input to Mixed Layer Near-Inertial Motions

2017 ◽  
Vol 47 (5) ◽  
pp. 1077-1093 ◽  
Author(s):  
Guoqiang Liu ◽  
William Perrie ◽  
Colin Hughes
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Wind Power ◽  
Mixed Layer ◽  
Single Point ◽  
Storm Track ◽  
Power Input ◽  
Momentum Fluxes ◽  
Wave Effects ◽  
Evolving Surface

AbstractOcean surface waves play an essential role in a number of processes that modulate the momentum fluxes through the air–sea interface. In this study, the effects of evolving surface waves on the wind-power input (WPI) to near-inertial motions (NIMs) are examined by using momentum fluxes from a spectral wave model and a simple slab ocean mixed layer model. Single-point numerical experiments show that, without waves, the WPI and the near-inertial kinetic energy (NI-KE) are overestimated by about 20% and 40%, respectively. Globally, the overestimate in WPI is about 10% during 2005–08. The largest surface wave effects occur in the winter storm-track regions in the midlatitude northwestern Atlantic, Pacific, and in the Southern Ocean, corresponding to large inverse wave age and rapidly varying strong winds. A relatively low frequency of occurrence of wind sea is found in the midlatitudes, which implies that the influence of evolving surface waves on WPI is intermittent, occurring less than 10% of the total time but making up the dominant contributions to reductions in WPI. Given the vital role of NIMs in diapycnal mixing at the base of the mixed layer and the deep ocean, the present study suggests that it is necessary to include the effects of surface waves on the momentum flux, for example, in studies of coupled ocean–atmosphere dynamics or climate models.

scholarly journals Toggling Near‐Field Directionality via Polarization Control of Surface Waves

2021 ◽  
Vol 15 (4) ◽  
pp. 2000388
Author(s):  
Yuhan Zhong ◽  
Xiao Lin ◽  
Jing Jiang ◽  
Yi Yang ◽  
Gui‐Geng Liu ◽  
...  
Keyword(s):  
Surface Waves ◽  
Near Field ◽  
Polarization Control

Guided Surface Waves on an Elastic Half Space

1971 ◽  
Vol 38 (4) ◽  
pp. 899-905 ◽  
Author(s):  
L. B. Freund
Keyword(s):  
Wave Propagation ◽  
Surface Wave ◽  
Surface Waves ◽  
Half Space ◽  
Body Wave ◽  
Three Dimensional ◽  
Elastic Half Space ◽  
Normal Displacement ◽  
Rigid Barrier ◽  
Wave Disturbances

Three-dimensional wave propagation in an elastic half space is considered. The half space is traction free on half its boundary, while the remaining part of the boundary is free of shear traction and is constrained against normal displacement by a smooth, rigid barrier. A time-harmonic surface wave, traveling on the traction free part of the surface, is obliquely incident on the edge of the barrier. The amplitude and the phase of the resulting reflected surface wave are determined by means of Laplace transform methods and the Wiener-Hopf technique. Wave propagation in an elastic half space in contact with two rigid, smooth barriers is then considered. The barriers are arranged so that a strip on the surface of uniform width is traction free, which forms a wave guide for surface waves. Results of the surface wave reflection problem are then used to geometrically construct dispersion relations for the propagation of unattenuated guided surface waves in the guiding structure. The rate of decay of body wave disturbances, localized near the edges of the guide, is discussed.

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