IEEE 211-1990 pdf free.IEEE Standard Definitions of Terms for Radio Wave Propagation.

IEEE 211 Fresnel ellipse，ellipsoid. (1) The locus ofpoints for which the sum of distances from twoantennas is an integral number of halfwavelengths greater than the length of thedirect ray between the two antennas. Theantennas are at the focal points of the set ofellipses，ellipsoids.(2)For a ground-reflected ray, the Fresnelellipse is the locus of points in the groundplane for which the sum of the distances fromthe two antennas is an integral number of halfwavelengths greater than the length of thespecularly reflected ray.Fresnel zone. In general，any surface orregion bounded by adjacent Fresnel ellipses orellipsoids. For instance，any plane throughboth antennas will intersect Fresnel ellipsesand define Fresnel zones in that plane. Anyplane normal to the ray path between antennaswill define a series of circular (annular)Fresnel zones.galactic radio waves. Radio waves originat-ing in our galaxy.

gravity wave.See: acoustic-gravity wave.grazing angle. The complement of the angleof incidence for large angles of incidence.

ground wave. From a source in the vicinity ofthe surface of the Earth, a wave that would existin the vicinity of the surface in the absence ofan ionosphere. Note: The ground wave can bedecomposed into the Norton surface wave anda space wave consisting of the vector sum of adirect wave and a ground-reflected wave.incident wave.A wave that impinges on adiscontinuity in refractive index or a mediumof different propagation characteristics.Theincident wave is the total field in the absenceof the discontinuity.

incoherent scattering.Scattering producedwhen an incident wave encounters randomfluctuations of complex dielectric constant.The fluctuations may be either discrete orcontinuous (turbid or turbulent in the case ofscattering from atmospheric refractive indexfluctuations). The scattered fields exhibitrandom variations in phase and amplitude.

inhomogeneous plane wave. A wave for whichthe planes of constant amplitude and planes ofconstant phase are not parallel. Sometimescalled a heterogeneous plane wave, but this useis deprecated.instantaneous frequency. 1/(2n) times thetime rate of change of phase of a wave.intrinsic impedance.See: impedance,intrinsic.ionogram. A record showing the group pathdelay of ionospheric echoes as a function offrequency.ionosonde. A swept-frequency or steppedfrequeney instrument that transmits radiowaves vertically or obliquely to the ionosphereand uses the echoes to form an ionogram.IEEE 211 pdf download.

# IEEE 211-1990 pdf free

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