Topic
Near and far field
About: Near and far field is a research topic. Over the lifetime, 15922 publications have been published within this topic receiving 220571 citations.
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18 Aug 1997TL;DR: In this paper, a THz imaging system with the emitter region of the THz generator designed so that the sample to be analyzed is placed in the near field of the generator allows radiation to impact the sample without intervening optics.
Abstract: A THz imaging system with the emitter region of the THz generator designed so that the sample to be analyzed is placed in the near field of the generator allows radiation to impact the sample without intervening optics.
47 citations
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TL;DR: In this paper, the extreme near-field behavior of the wire grid model of a conducting surface is examined, and it is verified that the best accuracy for the E-field is obtained when the wire satisfies the'same surface area' rule of thumb.
Abstract: The extreme near-field behavior of the wire grid model of a conducting surface is examined. Using a wire grid model of an infinite transverse magnetic circular cylinder, it is verified that the best accuracy for the E-field is obtained when the wire satisfies the 'same surface area' rule of thumb. Two excitations are considered: a uniform surface current and plane wave incidence. In the first case, although the boundary value match between the wires is poor the extreme near field is still quite accurate. In the second case, the near field is also accurate, however, the largest errors occur not between the wires, but in the interior of the scatterer. In both cases, the boundary match between the wires as a check on the accuracy of the solution is misleading. >
47 citations
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TL;DR: An optimal angle exists allowing one to maximize the electric near field, as well as the electric field enhancement factor in the immediate vicinity of the tip apex, based on finite-difference time-domain technique simulations of a silver conical nano-tip with a rounded end.
47 citations
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TL;DR: By correlating the magnitude of the received signal with the structured intensity patterns, high-fidelity, phaseless imaging of sparse targets is demonstrated, and it is shown that fields from such an aperture approximately obey speckle statistics in the radiative near field.
Abstract: We demonstrate a dynamic metasurface aperture as a unique tool for computational ghost imaging at microwave frequencies. The aperture consists of a microstrip waveguide loaded with an array of metamaterial elements, each of which couples energy from the waveguide mode to the radiation field. With a tuning mechanism introduced into each independently addressable metamaterial element, the aperture can produce diverse radiation patterns that vary as a function of tuning state. Here, we show that fields from such an aperture approximately obey speckle statistics in the radiative near field. Inspired by the analogy with optical correlation imaging, we use the dynamic aperture as a means of illuminating a scene with structured microwave radiation, receiving the backscattered intensity with a simple waveguide probe. By correlating the magnitude of the received signal with the structured intensity patterns, we demonstrate high-fidelity, phaseless imaging of sparse targets. The dynamic metasurface aperture as a novel ghost imaging structure can find application in security screening, through-wall imaging, as well as biomedical diagnostics.
47 citations
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TL;DR: In this article, the authors considered the inverse scattering problem of determining the shape of a perfect conductor from a knowledge of the scattered electromagnetic wave generated by a time-harmonic plane wave incident upon the conductor.
Abstract: We consider the inverse scattering problem of determining the shape of a perfect conductor D from a knowledge of the scattered electromagnetic wave generated by a time-harmonic plane wave incident upon D. By using polarization effects we establish the validity of the linear sampling method for solving this problem that is valid for all positive values of the wave number. We also show that it suffices to consider incident directions and observation angles that are restricted to a limited aperture. Copyright © 2003 John Wiley & Sons, Ltd.
47 citations