Results 181 to 190 of about 4,282 (222)
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The Bandwidth of Fresnel-Zone Plate Antennas
Journal of Electromagnetic Waves and Applications, 1997Theoretical expressions are presented for the illumination and phase efficiency of three types of Fresnel-zone plate antennas. Using these formulas, the bandwidths of the antennas will be analyzed and compared. Measured data are given to validate the theoretical results.
van Houten, J.M., Herben, M.H.A.J.
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Fresnel Zone Wavepath Tomography - Theory
The 3rd International Symposium on Recent Advances in Exploration Geophysics (RAEG 1998), 1998In this paper, a developing wavepath based on diffraction tomography in the space-time domain is presented. This wavepath is named Fresnel zone wavepath, derived from the imaginary part of Rhytov approximation. This wavepath is calculated using travel times from source to any point, receiver to any point and source to receiver.
B.E.B. Nurhandoko, Y. Ashida
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Image reconstruction from partial Fresnel zone information
Applied Optics, 1985An iterative algorithm for reconstructing an image from partial Fresnel zone information is discussed. With the standard 4-F canonical optical processor, processing is done midway between the two lenses in the Fourier transform plane. While others have studied reconstruction from partial Fourier plane information, we have investigated methods of ...
R, Rolleston, N, George
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SPIE Proceedings, 1985
A description is given of the use of the Fresnel zone plate as a focusing or a frequency-filtering device at millimeter wavelengths. Sample design data are given, as well as references to prior results. A newer type of zone plate is discussed which employs two dielectrics of equal thickness to produce a flat zone plate.
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A description is given of the use of the Fresnel zone plate as a focusing or a frequency-filtering device at millimeter wavelengths. Sample design data are given, as well as references to prior results. A newer type of zone plate is discussed which employs two dielectrics of equal thickness to produce a flat zone plate.
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Fresnel zone plate: Anomalous foci
American Journal of Physics, 1976It is found that, when a zone plate is examined in practice, foci exist where there should be none. An approach is developed which reveals that the zone plate is a circular diffraction grating, which in turn explains how a hologram works in a very direct manner.
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Nomogram for Fresnel‐zone calculation
GEOPHYSICS, 1980Geophysicists commonly recognize that a sizeable portion of a reflector is involved in causing a reflection as seen on a seismic trace, but the areal extent is usually not calculated and hence not appreciated. Most commonly, concepts are simply transferred from classical physical optics and called Fresnel‐zone effects.
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Fresnel zones in tapered gradient-index media
Journal of the Optical Society of America A, 2002The free propagation of a wave front in an inhomogeneous medium with parabolic refractive-index profile and the division of the wave front into Fresnel zones are studied. We determine the radius and the area of each zone as well as the zone contribution to the total wave at an observation point inside the medium.
José Manuel, Rivas-Moscoso +2 more
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2003
In the context of Huygens' principle and physical optics, it makes sense to consider a volume over which the phase of contributing waves is fairly constant, centred around the line-of-sight where the phase is stationary. Consider the situation in Figure D.l where the distance between the two antennas is d and the total distance to a scattering point is
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In the context of Huygens' principle and physical optics, it makes sense to consider a volume over which the phase of contributing waves is fairly constant, centred around the line-of-sight where the phase is stationary. Consider the situation in Figure D.l where the distance between the two antennas is d and the total distance to a scattering point is
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Fresnel Zone-Plate Diffraction Patterns
Journal of the Optical Society of America, 1969The diffraction patterns of the central aperture and the first 10 rings of the classical Fresnel zone plate are calculated in the principal focal plane for off-axis distances as large as the radius of the 10th ring. The zone-plate pattern is found by summation; near the axis it is compared with closed-form approximations.
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