The function of the antenna

The antenna radiates radio waves and receives them as well. However, the transmitter does not send radio waves to the antenna through the feed line, and the receiving antenna cannot directly send radio waves through the feed line to the receiver, which must go through an energy conversion process. Below, we will take wireless communication equipment as an example to analyze the signal transmission process and further illustrate the energy conversion effect of antennas.

At the transmitting end, the modulated high-frequency oscillation current (energy) generated by the transmitter is fed into the transmitting antenna (the feeding device can directly transmit current waves or electromagnetic waves depending on frequency and form), and the transmitting antenna converts the high-frequency current or guided waves (energy) into radio waves - free electromagnetic waves (energy) radiate into the surrounding space (see Figure 1); At the receiving end, radio waves (energy) are converted into high-frequency current or guided waves (energy) through the receiving antenna and transmitted to the receiver through feeding equipment. From the above process, it can be seen that the antenna is not only a device for radiating and receiving radio waves, but also an energy converter and an interface device between circuits and space.