Antenna Reactive Field: Capacitance, Inductance & Energy

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SUMMARY

The discussion centers on the behavior of antennas as RCL circuits, emphasizing the roles of radiation resistance (R), inductance (L), and capacitance (C) in the reactive fields surrounding antennas. It is established that the reactive fields do not need to store equal amounts of energy, and that both capacitive and inductive components can vary independently. The conversation also highlights that any structure capable of radiating electromagnetic energy, including real capacitors and inductors, can function as antennas. The complexity of determining the distribution of reactive energy in simple Hertzian dipoles is acknowledged, indicating that both capacitive and inductive parameters are distributed and not easily quantifiable.

PREREQUISITES
  • Understanding of RCL circuit theory
  • Familiarity with electromagnetic radiation principles
  • Knowledge of reactive fields in antennas
  • Basic concepts of time-varying electric and magnetic fields
NEXT STEPS
  • Research the characteristics of Hertzian dipoles and their reactive fields
  • Explore the relationship between energy storage in capacitive and inductive fields
  • Study the implications of distributed parameters in antenna design
  • Learn about the practical applications of antennas in electromagnetic radiation
USEFUL FOR

Electrical engineers, antenna designers, and researchers in electromagnetic theory will benefit from this discussion, particularly those focused on the reactive properties of antennas and their energy storage capabilities.

fisico30
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An antenna behaves like an RCL circuit.
The R is the radiation resistance corresponding to energy actually radiate. Half come from the E field and half from the B field.

The L and C are responsible for the reactive field close to the antenna. the C tells about the energy stored in the E field attached to the antenna.
The L about the B field.

Do the capacitative and inductive reactive fields store energy in the amount?
Do some antennas have more energy in one or the other? Any example? Can we have an antenna with only inductive reactive field and no C field?
Is it correct to say that the reactive field is time-varying (almost in phase with the source since it is so close) and looks like the electrostatic+magnetostatic field?
thanks
 
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Any structure that radiates electromagnetic energy can be considered an antenna in the context of your question. Therefore a (real, not ideal) capacitor is antenna, because any such structure can be made radiate to some degree; a real inductor is similarly a radiator.

So clearly, for a given structure the capacitive and inductive fields do not have to be equal in terms of stored energy.

Time varying charge densities and current densities give rise to time varying electrostatic and magnetostatic fields in addition to electromagnetic radiation.
 
ak7948 you are very clear. But how about the simple Hertian dipole? It current is time changing (sinusoidally). Does its reactive field have more C reactive energy or L reactive energy? I guess the C and the L are distributed parameters and it is not easy to det. how much each one is.
 

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