intensity is one-half the maximum value". The Half-power beamwidth is also
commonly referred to as the 3-dB beamwidth.
Antenna directivity: The directivity of an antenna is given by the ratio of the
maximum radiation intensity (power per unit solid angle) to the average radiation
intensity (averaged over a sphere). The directivity of any source, other than
isotropic, is always greater than unity.
Antenna gain: The maximum gain of an antenna is simply defined as the product of
the directivity by efficiency. If the efficiency is not 100 percent, the gain is less than
the directivity. When the reference is a loss less isotropic antenna, the gain is
expressed in dBi. When the reference is a half wave dipole antenna, the gain is
expressed in dBd (1 dBd = 2.15 dBi ).
Antenna efficiency: The total antenna efficiency accounts for the following losses:
(1) reflection because of mismatch between the feeding transmission line and the
antenna and (2) the conductor and dielectric losses.
Effective radiated power (ERP): "In a given direction, the relative gain of a
transmitting antenna with respect to the maximum directivity of a half-wave dipole
multiplied by the net power accepted by the antenna from the connected
transmitter".
Power handling: Is the ability of an antenna to handle high power without failure.
High power in antenna can cause voltage breakdown and excessive heat (due to
conductor and dielectric antenna losses) which would results in an antenna failure.
Passive intermodulation (PIM): As in active devices, passive intermodulation
occurs when signals at two or more frequencies mix with each other in a non-linear
manner to produce spurious signals. PIM is caused by a multitude of factors present
in the RF signal path. These include poor mechanical contact, presence of ferrous
contents in connectors and metals, and contact between two galvanically unmatched
metals. PIM spurious signal, which falls in the up link band, can degrade call quality
and reduce the capacity of a wireless system.
Side lobe suppression: "Any process, action or adjustment to reduce the level of
the side lobes or to reduce the degradation of the intended antenna system
performance resulting from the presence of side lobes". For base station antenna,
the first side lobe above the horizon is preferred to be low in order to reduce
interference to adjacent cell sites. At the other hand, the side lobes below the
horizon are preferred to be high for better coverage.
Null filling: Is the process to fill the null in the antenna radiation pattern to avoid
blind spots in cell site coverage.
Isotropic radiator: "A hypothetical, loss less antenna having equal radiation
intensity in all direction". For based station antenna, the gain in dBi is referenced to
that of an isotropic antenna (which is 0 dB).