What’s the antenna of Contents

what is the antenna

An antenna is a device that can effectively radiate electromagnetic waves to a specific direction in space or can effectively receive electromagnetic waves from a specific direction in space.

We use the analogy of communication between people. The antenna is our ears and mouth. We convert the sound into sound waves and send them out through the mouth. The sound waves propagate in the air and are finally heard by our ears. In the communication system, the antenna plays the role of the mouth and the ear. The difference is that the antenna can both transmit and receive electromagnetic waves.

The principle of the antenna

The antenna transforms the guided waves propagating on the transmission line into electromagnetic waves propagating in free space, or vice versa. A guided wave is an electromagnetic wave in which all or most of the electromagnetic energy is confined in a finite cross-section and propagates in a certain direction.

We use the analogy of train travel, where the passengers are electromagnetic waves and the transmission line is the train.

After getting on the train, the passenger can only move in the car, and the passenger moves with the direction of the train, which is like a guided wave, which is constrained to transmit in a certain direction within a limited cross-section.

After leaving the station, passengers can move freely, which is like electromagnetic waves propagating in free space. Here the train door is like an antenna.

Train doors can be used for both boarding and alighting of passengers.

Similarly, the antenna can be used to convert guided waves into free space electromagnetic waves and free space electromagnetic waves into guided waves, which is the principle of reciprocity of antennas

How does an antenna convert guided waves into electromagnetic waves in free space?

In 1894, the scientist Popov found in an experiment that the distance at which the receiver could detect the radio wave was significantly increased than usual. After some probing, Popov discovered that a wire had hit the chip detector. It is this wire that allows the experimental distance to be greatly increased. This wire is considered the world’s first antenna.

In Popov’s experiment, the wire accidentally hit the metal chip detector, which changed the shape of the transmission line.

Following the idea of Popov’s experiment, scientists found that as the opening angle of the transmission line increases, the radiated electromagnetic waves are stronger. Later, the theory of symmetrical oscillator antennas was proposed, and various antennas were developed.