In an antenna, current flows through its conductive elements, which leads to the radiation of electromagnetic (EM) waves. The process can be described as follows:
Source of Current: An antenna is connected to a power source or a transmitter that generates an alternating current (AC). This current is typically at radio frequencies.
Conductive Elements: The antenna consists of conductive elements, such as metal rods, wires, or loops, which are designed to efficiently radiate EM waves. These elements are often arranged in specific patterns or configurations, depending on the type of antenna.
Oscillation of Current: The alternating current from the source causes electrons within the conductive elements to oscillate back and forth. This oscillating current creates a constantly changing electric field around the antenna.
Creation of Electromagnetic Waves: As the electrons oscillate, the changing electric field induces a magnetic field perpendicular to it, according to Maxwell's equations. These two fields, the electric field and the magnetic field, oscillate together and are mutually reinforcing, giving rise to an electromagnetic wave.
Radiation Pattern: The specific arrangement and geometry of the antenna elements determine the directionality and pattern of the radiated EM wave. Different types of antennas have different radiation patterns, which can be omnidirectional (radiating in all directions equally) or directional (radiating in a specific direction).
Propagation of EM Wave: Once the EM wave is generated, it propagates through space at the speed of light. The radiated wave carries the energy and information encoded in the original current.
It's important to note that the process of how current flows in an antenna and how it radiates EM waves is a complex electromagnetic phenomenon. It involves concepts from classical electromagnetism, including Maxwell's equations, which describe the relationship between electric and magnetic fields and their propagation. Antenna design and engineering further optimize the efficiency and performance of the radiation process.