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1) The deviation of an electromagnetic wavefront from the path predicted by geometric optics when the wavefront interacts with, i.e. , is restricted by, a physical object such as an opening (aperture) or an edge. 2) Phenomenon that occur when radio waves encounter obstacles. On encountering an obstacle during propagation in a homogeneous medium, a radio wave changes in amplitude and phase and penetrates the shadow zone, deviating from a straight path.
The wave propagating directly between the transmitting and receiving antenna, without affecting any objects on the traveling path of electromagnetic wave ray. In the case of propagation over the surface of the Earth is a component of space wave.
Direction, in which an antenna pattern reaches its maximum.
Antenna which radiates (or receives) greater power in one or more directions (allowing for increased performance on transmit and receive and reduced interference from unwanted sources).
Parameter defined as the ratio of the maximum density of radiation (received power) to the average density of radiation (received power) in lossless antenna.
Ability of antenna to direct radio waves in one direction or receive from a single direction.
Any electromagnetic phenomenon which may degrade the performance of a device, equipment or system, or adversely affect living or inert matter. An electromagnetic disturbance may be electromagnetic noise, an unwanted signal or a change in the propagation medium itself.
The change in the observed frequency (or wavelength) of a wave, caused by a time rate of change in the path length between the source and the point of observation.
1) A unidirectional transmission channel from central station to terminal station. 2) In the context of land mobile radiocommunication: the transmission channel from one base station to one or more mobile stations. 3) In the context of satellite communications: the portion of a communications link used for the transmission of signals from a satellite to a ground station.
DL (D/L)
Tilt the antenna radiation pattern to reduce interference in (cellular) radio network. The tilt can be held by a mechanical or electrical way. Electrical tilting slightly reduces beam width.