Antenna Reactive Field: Capacitance, Inductance & Energy

In summary, an antenna is similar to an RCL circuit, with the radiation resistance (R) corresponding to the energy radiated, and the inductive (L) and capacitive (C) components responsible for the reactive fields close to the antenna. The C field indicates the energy stored in the electric field attached to the antenna, while the L field indicates the energy stored in the magnetic field. The amount of energy stored in each component can vary, and therefore some antennas may have more energy in one component than the other. It is possible to have an antenna with only an inductive reactive field and no capacitive field. The reactive field is time-varying and is in phase with the source, resembling the electrostatic and magnetost
  • #1
fisico30
374
0
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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  • #2
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.
 
  • #3
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.
 

1. What is an antenna reactive field?

An antenna reactive field refers to the region of space surrounding an antenna that is affected by the electric and magnetic fields generated by the antenna. This field is responsible for the transmission and reception of electromagnetic waves.

2. What is capacitance in relation to antenna reactive field?

Capacitance is the ability of a conductor to store electrical energy in the form of an electric charge. In relation to antenna reactive field, capacitance is a measure of the ability of an antenna to store electrical energy in the form of an electric field.

3. What is inductance in relation to antenna reactive field?

Inductance is the property of a conductor that opposes changes in current. In relation to antenna reactive field, inductance is a measure of the ability of an antenna to store electrical energy in the form of a magnetic field.

4. How do capacitance and inductance affect the energy of an antenna reactive field?

Capacitance and inductance are both components of the impedance of an antenna, which determines the efficiency of energy transfer between the antenna and the surrounding space. Changes in capacitance and inductance can affect the energy of an antenna reactive field by altering the impedance and thus the efficiency of energy transfer.

5. Can the antenna reactive field be manipulated to improve antenna performance?

Yes, the antenna reactive field can be manipulated through the use of tuning elements such as capacitors and inductors. By adjusting the capacitance and inductance of an antenna, the impedance and efficiency of energy transfer can be optimized, leading to improved antenna performance.

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