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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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TL;DR: In this article, an efficient time-domain near-zone-to-far-zone transformation for FDTD (finitedifference-time-domain) computations is presented, which is based on keeping a running accumulation of the far-zone timedomain vector potentials due to the tangential electric and magnetic fields on a closed surface surrounding the scatterer at each time step.
Abstract: An efficient time-domain near-zone-to-far-zone transformation for FDTD (finite-difference-time-domain) computations is presented. The approach is to keep a running accumulation of the far-zone time-domain vector potentials due to the tangential electric and magnetic fields on a closed surface surrounding the scatterer at each time step. At the end of the computation, these vector potentials are converted to time-domain far-zone fields. Many far-zone bistatic directions can be included efficiently during one FDTD computational run. Frequency domain results can be obtained via fast Fourier transform. Wideband results for scattering from a perfectly conducting plate were obtained from a single FDTD computation transformed to the frequency domain, and compared with moment method results. This approach is significantly more efficient than computing many FDTD results using sinusoidally varying excitation if a wide frequency band is of interest. Coupled with recent advances in computing FDTD results for frequency-dependent materials, wideband results for far-zone scattering from targets including frequency-dependent materials can be obtained efficiently. >
294 citations
TL;DR: In this paper, the authors discuss the properties of electromagnetic fields in heavy-ion collisions and consequences for observables, including quantitatively the issue of the magnetic field lifetime in a collision including the electric and chiral magnetic conductivities.
294 citations
TL;DR: 3D numerical calculations demonstrate that the interaction of a single quantum emitter with the electromagnetic field is both enhanced and directed by a nano-optical Yagi-Uda antenna, making such antennas a promising candidate for compact easy-to-address planar sensors.
Abstract: We demonstrate by 3D numerical calculations that the interaction of a single quantum emitter with the electromagnetic field is both enhanced and directed by a nano-optical Yagi-Uda antenna. The single emitter is coupled in the near field to the resonant plasmon mode of the feed element, enhancing both excitation and emission rates. The angular emission of the coupled system is highly directed and determined by the antenna mode. Arbitrary control over the main direction of emission is obtained, regardless of the orientation of the emitter. The directivity is even more increased by the presence of a dielectric substrate, making such antennas a promising candidate for compact easy-to-address planar sensors.
289 citations
Patent•
AT&T1
TL;DR: In this paper, an apparatus including a waveguide, an antenna, and a transmitter can be used to facilitate propagation of the first electromagnetic waves at least in part on a surface of the waveguide.
Abstract: Aspects of the subject disclosure may include, for example, an apparatus including a waveguide, an antenna, and a transmitter. The transmitter can facilitate transmission of first electromagnetic waves via the antenna, the first electromagnetic waves having a fundamental mode. The waveguide can facilitate propagation of the first electromagnetic waves at least in part on a surface of the waveguide. The waveguide can be positioned at a location that enables the first electromagnetic waves to induce second electromagnetic waves having fundamental and non-fundamental modes that propagate on a surface of a transmission medium. Other embodiments are disclosed.
282 citations
TL;DR: In this article, the authors proposed a system to enable the signature of an air gun array to be calculated at any point in the water from a number of simultaneous independent measurements of the near-held pressure held.
Abstract: We designed a system to enable the signature of an air gun array to be calculated at any point in the water from a number of simultaneous independent measurements of the near-held pressure held [subject of a patent application]. The number of these measurements must not be less than the number of guns in the array. The underlying assumption in our method is that the oscillating bubble produced by an air gun is small compared with the wavelengths of seismic interest. Each bubble thus behaves as a point source, both in the generation of seismic waves and in its response to incident seismic radiation produced by other nearby bubbles. It follows that the intcraction effects between the bubbles may be described in terms of spherical waves. The array of interacting guns is equivalent to a notional array of noninteracting guns whose combined seismic radiation is identical. The seismic signatures of the equivalent independent elements of this notional array can be determined from the near-held measurements. The seismic radiation pattern emitted by the whole array can be computed from these signatures by linear superposition, with a spherical correction applied. The method is tested by comparing far-field signatures computed in this way with field measurements made in deep water. The computed and measured signatures match each other very closely. By comparison, signatures computed neglecting this interaction are a poor match to the
280 citations