The antenna is a special device that converts electromagnetic in a transmission line into electromagnetic waves in free space, or converts electromagnetic waves in space into electromagnetic energy in a transmission line.
In the satellite communication,the antenna performance is in a very import position in the whole network operating quality. Therefore quality of the satellite communication is naturally closely related to the antenna performance.But do you know what will impact the antenna performance?Let's learn it together.
1.The antenna radiation pattern
The electromagnetic wave radiated by the antenna is directional,which indicates the ability of the antenna to radiate electromagnetic waves to a certain direction.Conversely, the directivity of the receiving antenna indicates its ability to receive electromagnetic waves from different directions.We usually use curves indicated the power of electromagnetic waves radiated (or received) in different directions on the vertical plane and the horizontal plane to express the directivity of the antenna, which is called the antenna radiation pattern.At the same time, the angle between the half power points is used to indicate the horizontal beam width and the vertical beam width in the antenna pattern.
2. The antenna gain
The antenna is usually a passive device, it does not amplify electromagnetic signals. The gain of the antenna is the ratio of the received power at the same point under the same input power conditions after the antenna radiated electromagnetic waves are bundled compared to an ideal reference antenna. Obviously the gain is related to the antenna pattern. The narrower the main beam in the pattern, the smaller the side lobe and tail lobe, the higher the gain. It can be seen that the high gain is at the cost of reducing the irradiation range of the antenna beam.
3. The antenna VSWR
The antenna VSWR is an indicator of the matching degree between the antenna feeder and the base station (transceiver). The VSWR is caused by that the incident wave energy is transmitted to the antenna input terminal and is not completely absorbed (radiated), resulting in reflected waves, which are superimposed. The greater the VSWR, the greater the reflection and the worse the matching. So, what are the disadvantages of poor VSWR? What is the acceptable VSWR in engineering? One is that the VSWR index is a trade-off between the amount of energy lost and the manufacturing cost.
4. The antenna polarization
The direction of the electric field in the electromagnetic wave radiated by the antenna is the polarization direction of the antenna. Since the orientation of the electric field when electromagnetic waves propagate in free space is vertically linear polarization, horizontally linear polarization, and circular polarization, so the antenna is the corresponding vertical linear polarization antenna and horizontal linear polarization antenna. For the dual-polarized antenna, It is an antenna with horizontal linear polarization and vertical linear polarization under a radome.
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