5. Glossary

Antenna radiation; antenna radiation

Away from the antenna, radiation can be considered locally as the propagation of a plane wave. The electric and magnetic fields then form a direct trihedron with the wave vector. The ratio of the amplitudes of the electric and magnetic fields gives the wave impedance of the medium (in a vacuum 377 Ω).

Directivity

The directivity D ₀ is the ratio between the radiation intensity in the direction of the main lobe's radiation maximum and the total radiated power.

Gain; gain

The gain (or power gain or absolute gain) G is the ratio between the radiation intensity in the direction of maximum radiation from the main lobe and the total power injected into the antenna:

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