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Antenna Characteristics
Isotropic Antenna
A hypothetical antenna having equal radiation intensity in all directions. Used as a
zero dB gain reference in directivity calculation (gain).
Antenna Gain
A measure of directivity. It is defined as the ratio of the radiation intensity in a given
direction to the radiation intensity that would be obtained if the power accepted by
the antenna was radiated equally in all directions (isotropically). Antenna gain is
expressed in dBi.
Radiation Pattern
A graphical representation in either polar or rectangular coordinates of the spatial
energy distribution of an antenna.
Side Lobes
The radiation lobes in any direction other than that of the main lobe.
Directional Antenna
Radiates and receives most of the signal power in one direction. The following
diagram shows the radiation pattern of a directional antenna with its side lobes in
polar form:
Figure 29: Radiation Pattern of Directional Antenna
Antenna Beamwidth
The directiveness of a directional antenna. Defined as the angle between two
half-power (-3 dB) points on either side of the main lobe of radiation.
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