AdvancedA-007-008-001
What is meant by the radiation resistance of an antenna?
A
Answer
Interference, EMC, and safety
Type
A
The equivalent resistance that would dissipate the same amount of power as that radiated from an antenna
B
The resistance in the atmosphere that an antenna must overcome to be able to radiate a signal
C
The specific impedance of an antenna
D
The combined losses of the antenna elements and transmission line
Answer Notes
Radiation resistance is a theoretical concept used in antenna engineering to represent the power actually radiated into space. It is defined as the equivalent fictitious electrical resistance that would dissipate the exact same amount of power as heat that the antenna radiates as electromagnetic waves.
In an equivalent circuit model of an antenna, the total resistance consists of radiation resistance and ohmic (loss) resistance. The power 'lost' to radiation resistance is the useful radio signal.
Distractors often suggest this relates to physical air resistance, atmospheric impedance, or the ohmic losses of the physical wire. Those are incorrect; radiation resistance solely represents the useful radiated RF energy.
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Why would one need to know the radiation resistance of an antenna?