Re: Antenna's work
Radiation mechanism of antenna.......
When electric current of high frequency is passed through a conductor, the electrons are forced to oscillate at the signal frequency (which is to be radiated !!).
1.
During the + ve half cycle of the signal, an electron is accelerated and during the following -ve one, it is retarded.Thus the field (static field at dc signal level) around the electron is perturbed continuously and periodically.
2.
An accelerated electron is shifted to a higher energy level in the conduction band .When it is retarded, the excess energy is emitted (in order to come back to the original state)in the form of electromagnetic radiation at the applied the signal frequency.
3.
When an electron moves at a constant velocity, field lines do not bend (reactive field) while when it is accelerated (reactive + radiating field), they bend. At each position of the accelerated electron, the field around it updates to the new value. The difference in field value around the electron of the present and the immediate past positions is radiated at the speed of light.
One more fact, this is not a complete explanation
pran