How much current can you draw from a resonant loop antenna

Click For Summary
SUMMARY

The discussion centers on the current draw from a resonant loop antenna, highlighting the phase relationship between the antenna's magnetic field and the incoming electromagnetic (EM) wave. In a resonant antenna, a 90-degree phase shift exists, which affects the current draw. Theoretical limits on current are established due to the finite energy contained in the fields, which can be extracted based on the antenna's effective aperture. The relationship between voltage and current can be modeled using the equation I = Vout/R, where R represents the load resistance in a resistive LRC circuit.

PREREQUISITES
  • Understanding of electromagnetic wave theory
  • Familiarity with loop antenna design and operation
  • Knowledge of resonant circuits and impedance
  • Basic principles of LRC circuit analysis
NEXT STEPS
  • Research the principles of electromagnetic field theory
  • Study the design and characteristics of resonant loop antennas
  • Explore the mathematical modeling of LRC circuits
  • Learn about effective aperture and its impact on antenna performance
USEFUL FOR

Electrical engineers, antenna designers, and researchers in electromagnetic theory will benefit from this discussion, particularly those focusing on antenna efficiency and current extraction methods.

htg
Messages
107
Reaction score
0
In the case of a loop antenna with uncompensated inductance, the magnetic field generated by the current in the antenna is in antiphase to the incoming magnetic field of the EM wave. So it is believable that the current which causes cancellation of the flux through the antenna is the maximum current that you can draw.
But in the case of a resonant antenna, there is 90 degrees phase shift between the magnetic field generated by the current in the antenna and the magnetic field of the incoming EM wave. In the idealized situation (no resistance, neglecting radiation by the receiving antenna) is there any limit on the current?
(Or does it behave like I0*t*sin(2*Pi*f*t) if the induced voltage is U0*sin(2*Pi*f*t) ?).
 
Physics news on Phys.org
There is always going to be some implied limit on the current. For example, there is only a finite amount of energy contained in the fields that can be extracted to generate the currents. One can consider the equivalent sources of the fields to be in the form of currents and charges and given that the total energy contained in the fields is finite then the equivalent energy from the sources must also be finite. This ignores the fact that any receiving antenna can only capture the fields incident upon their effective aperture which further reduces the amount of energy that can be extracted out of the fields.
 
You could use the equation for a (parallel or series) resistive LRC circuit, and use R as the resistance (load) of the external circuit. The circulating current for a series R in the loop is then I = Vout/R.

Bob S
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
7K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 1 ·
Replies
1
Views
1K
Replies
12
Views
2K
  • · Replies 13 ·
Replies
13
Views
3K