Radiation mechanism in single-wire antennas

Radiation mechanism:

When transmitting and receiving antenna is excited with an alternating voltage, then the initial move will be started by the balanced motion of charges in the antenna. Resonant oscillations are produced by the supplied energy.

Electric and magnetic fields are generated due to sudden changes in charge. When the charges around the antenna are set in motion. The disturbance is spread from the antenna into space. The electric and magnetic fields so produced are perpendicular to each other in space. EM waves don't have boundaries. EM wave energy decreases as it propagates.

Radiation mechanism in single-wire:

It is a fundamental single wire antenna. By the principle of radiation, the current must be time-varying.

For a single wire antenna:

• If the charge is stationary, no current is developed. So no radiation is observed.
• If the charge is moving with uniform velocity, then : 

       i) No radiation occur for a straight wire which is infinity in extent

       ii) Radiation is possible only if the wire is curved; bent, discontinuous, terminated or truncated.

When a wire is energized using a source, the free electrons in wire are set into motion due to the force of electrical lines.

The charges will be accelerated at the source end while they are decelerated due to the reflection at the other end. As a result, radiation fields are created not only at the two ends but also along the remaining part of the wire.

If the pulses of charge traveling along the wire are narrow, then radiation is stronger with a wide frequency spectrum. But if the charge is oscillating, then the radiation of a single frequency is produced.

fig., different wire configurations producing radiation

Disclaimer:

I have created this blog for educational purposes, so for that, I have written the content by referring many books, web pages. I have also uploaded google images for a better understanding of the concept and I would also like to inform you that I am not responsible for the ads which are being posted on my blog.