A radar antenna is a microwave system, that radiates or receives energy in the form
of electromagnetic waves.
Reciprocyty of radar antennas means that the various properties of the antenna apply
equally to transmitting and receiving.
Parabolic reflectors („dishes”) and phased arrays are the two basic
constructions of radar antennas.
Antennas fall into two general classes, omnidirectional and directional.
Omnidirectional antennas radiate rf energy in all directions simultaneously.
Directional antennas radiate rf energy in patterns of lobes or beams that extend
outward from the antenna in one direction for a given antenna position.
Radiation patterns can be plotted on a rectangular- or polar-coordinate graph.
These patterns are a measurement of the energy leaving an antenna.
An isotropic radiator radiates energy equally in all directions.
An anisotropic radiator radiates energy directionally.
The main lobe is the boresight direction of the radiation pattern.
Side lobes and the back lobe are unwanted areas of the radiation pattern.
