Antenna is used to transmit signals from base stations and mobile phones. In prehistoric times, the tallest building in every city must be a TV tower. Television also receives signals from the TV tower through antennas. The two whip antennas with the same antennas on the top of the antenna form many people’s initial impression of the antenna.
There are all kinds of different types of antennas, according to different classification methods can give different types.
1. The antenna can be divided into transmitting antenna and receiving antenna according to its working nature.
2. It can be divided into communication antenna, broadcast antenna, television antenna, radar antenna and so on.
3. Directional antenna can be divided into omnidirectional antenna and directional antenna.
4. According to the working wavelength, it can be divided into ultra-long wave antenna, long wave antenna, medium wave antenna, short wave antenna, ultra-short wave antenna, microwave antenna and so on.
5. According to the structure and working principle, it can be divided into wire antenna and plane antenna.
6. According to the dimension, it can be divided into two types: one-dimensional antenna and two-dimensional antenna.
7. Antennas can be divided into three categories: handheld antenna, vehicle antenna and base antenna.
The reason why the antenna can transmit information at high speed is that it can transmit the electromagnetic wave carrying information into the air, propagate at the speed of light, and finally reach the receiving antenna.
It’s like transporting passengers by high-speed train. If we compare information to passengers, then the means of transporting passengers: high-speed train is electromagnetic wave, and antenna is equivalent to station, responsible for managing and dispatching the transmission of electromagnetic wave.
So what is electromagnetic wave?
Scientists have studied the two mysterious forces of electricity and electromagnetism for hundreds of years. Finally, Maxwell of England put forward that electric current can produce electric field around it, changing electric field can produce magnetic field, and changing magnetic field can produce electric field. The theory was finally confirmed by Hertz’s experiments.
In such periodic transformation of electromagnetic field, electromagnetic wave radiates and propagates to space.
But in fact, the coverage of our base station needs to be farther in the horizontal direction, after all, the callers are all on the ground; the vertical direction is high, and there is no need for people flying while shaking in the high air (airline coverage is another topic, I will talk about it next time). Therefore, in the transmission of electromagnetic wave energy, we need to We should strengthen the horizontal direction and weaken the vertical direction.
According to the principle of energy conservation, the energy will neither increase nor decrease. If the emission energy in horizontal direction is to be increased, the energy in vertical direction will be weakened. Therefore, only the energy radiation pattern of the standard half-wave array is flattened, as shown in the following figure.
Directional antenna is widely used in general macro base station systems. Generally, a base station is divided into three sectors, covered by three antennas, each covering a range of 120 degrees.
Post time: Jul-23-2019