4G and 5G base station antenna application scenarios | 4g lte antenna
Classification of base station antennas
Omnidirectional antenna: in the horizontal pattern, it shows 360 ° uniform radiation, that is, no directivity. In the vertical pattern, it shows a beam with a certain width. Generally, the smaller the lobe width, the greater the gain. Omnidirectional antenna is generally used in mobile communication systems, which is similar to the station type in suburban counties and regions, and has a large coverage.
Directional antenna: It shows radiation in a certain angle range in the horizontal pattern, that is, directivity in general. It shows a beam with a certain width in the vertical pattern. Like omnidirectional antenna, the smaller the lobe width, the greater the gain. Directional antenna is generally used in the mobile communication system for the station type of urban cell system, with small coverage, high user density and high frequency utilization.
Different types of base stations are established according to the requirements of networking, and different types of antennas can be selected for different types of base stations. The selection is based on the above technical parameters. For example, omnidirectional station adopts omnidirectional antenna with basically the same gain in each horizontal direction, while directional station adopts directional antenna with obvious change in horizontal gain. Generally, antennas with a horizontal beam width of 65 ° are selected in urban areas. In suburban areas, antennas with a horizontal beam width of 65 °, 90 ° or 120 ° can be selected (depending on the station type configuration and local geographical environment). In rural areas, it is most economical to select omnidirectional antennas that can achieve wide coverage. 4g lte antenna
Mechanical antenna: refers to the mobile antenna that uses mechanical adjustment for downward tilt angle. After the mechanical antenna is installed vertically with the ground, if the network optimization requires, the position of the support on the back of the antenna needs to be adjusted to change the angle of the antenna. In the adjustment process, although the coverage distance in the main lobe direction of the antenna changes significantly, the amplitude of the vertical and horizontal components of the antenna remain unchanged, so the antenna pattern is easy to deform.
The practice proves that the optimum declination angle of the mechanical antenna is 1 ° - 5 °; When the down tilt angle changes from 5 ° to 10 °, the antenna pattern is slightly deformed but has little change; When the down tilt angle changes from 10 ° to 15 °, the antenna pattern changes greatly; When the mechanical antenna is tilted down 15 °, the shape of the antenna pattern changes greatly, from Yali when it is not tilted down to a spindle. At this time, although the coverage distance in the main lobe direction is significantly shortened, the entire antenna pattern is not all in the sector of the BTS, and the signals of the BTS will also be received in the sector of the adjacent BTS, causing serious interference in the system. In addition, in daily maintenance, if the mechanical antenna tilt angle is to be adjusted, the whole system should be shut down, and monitoring cannot be performed while adjusting the antenna tilt angle; It is very troublesome for the mechanical antenna to adjust the antenna declination angle, which generally requires the maintenance personnel to climb to the antenna location for adjustment; The declination angle of the mechanical antenna is the theoretical value calculated by computer simulation analysis software, which has a certain deviation from the actual optimal declination angle; The number of steps for the mechanical antenna to adjust the tilt angle is 1 °, and the third-order intermodulation index is - 120dBc.
Electrically adjustable antenna: refers to a mobile antenna that uses electronic adjustment for downward tilt angle. The principle of electronic downtilt is to make the vertical pattern of the antenna downtilt by changing the phase of the dipole of the collinear array antenna, changing the amplitude of the vertical component and the horizontal component, and changing the field strength of the composite component. As the field strength in all directions of the antenna increases and decreases at the same time, it ensures that the antenna pattern does not change much after changing the tilt angle, which shortens the coverage distance in the main lobe direction. At the same time, it reduces the coverage area of the entire directional pattern in the service cell sector without interference. Practice has proved that the antenna pattern of electrically adjustable antenna is roughly the same as that of mechanical antenna when the downward inclination angle of the antenna varies from 1 ° to 5 °; When the down tilt angle changes from 5 ° to 10 °, the antenna pattern is slightly improved compared with the mechanical antenna; When the down tilt angle changes from 10 ° to 15 °, the antenna pattern changes more than that of mechanical antenna; When the mechanical antenna is tilted down by 15 °, its antenna pattern is significantly different from that of the mechanical antenna. At this time, the shape of the antenna pattern changes little, and the coverage distance in the main lobe direction is significantly shortened. The entire antenna pattern is in the sector of the BTS. Increasing the tilt angle can reduce the sector coverage area without interference. Therefore, using the electrically tuned antenna can reduce call loss and interference. In addition, the electrically adjustable antenna allows the system to adjust the dip angle of the vertical directivity map without stopping the machine, monitor the effect of adjustment in real time, and the step accuracy of adjusting the dip angle is also high (0.1 °), so the network can be fine adjusted; The third-order intermodulation index of electrically tuned antenna is - 150 dBc, which is 30 dBc different from that of mechanical antenna, which is conducive to eliminating adjacent frequency interference and stray interference.
Bipolarized antenna: Bipolarized antenna is a new antenna technology, which combines two mutually orthogonal antennas with polarization directions of+45 ° and - 45 ° and works in the transceiver duplex mode at the same time. Therefore, its most outstanding advantage is to save the number of antennas of a single directional base station; Generally, the directional base station (three sectors) of the LTE digital mobile communication network uses 9 antennas, and each sector uses 3 antennas (spatial diversity, one transmitter and two receivers). If dual polarized antennas are used, only one antenna is required for each sector; At the same time, because the polarization orthogonality of ± 45 ° in the dual polarized antenna can ensure that the isolation between the two antennas of+45 ° and - 45 ° meets the requirements of intermodulation for the isolation between antennas (≥ 30dB), so the space interval between dual polarized antennas only needs 20-30cm; In addition, the dual polarized antenna has the advantages of electrically adjusted antenna. The use of dual polarized antenna in mobile communication network is the same as that of electrically adjusted antenna, which can reduce call loss, reduce interference and improve the service quality of the whole network. If the dual polarized antenna is used, since the dual polarized antenna does not have high requirements for erection and installation, land acquisition and tower construction are not required. Instead, an iron pillar with a diameter of 20cm needs to be erected, and the dual polarized antenna can be fixed on the iron pillar according to the corresponding coverage direction, thus saving infrastructure investment, making the layout of the base station more reasonable, and making the selection of the base station site easier.
For the selection of antennas, mobile antennas suitable for the needs of the local mobile network should be selected according to the actual situation of network coverage, traffic, interference and network service quality:
·In areas with dense base stations and high traffic, dual polarized antennas and electrically modulated antennas should be used as much as possible;
·Traditional mechanical antennas can be used in areas where the traffic volume is not high, where the base stations are not dense, or where coverage is only required.
