At present, in the construction and maintenance of GSM network, how to solve the problem of capacity and interference in high traffic density area of GSM network, improve the connection rate of the whole network, reduce the drop-out rate and improve the quality of calls has become the focus and difficulty of recent work. Using appropriate antenna technology will be one of the methods that can effectively control the coverage, reduce co-frequency interference and improve the reception effect of mobile phone signals.

What is a bipolar antenna?
Dual-polarized antenna is a new type of antenna technology, which combines two pairs of antennas with orthogonal polarization directions of + 45 and - 45 and works in the mode of receiving and receiving duplex at the same time. Therefore, the most prominent advantage of dual-polarized antenna is to save the number of antennas of a single directional base station. In general, the directional base station (three sectors) of GSM digital mobile communication network uses nine antennas, and If the dual-polarized antenna is used, only one antenna is needed for each sector; meanwhile, in the dual-polarized antenna, the polarization orthogonality of (+45) can ensure that the isolation between the two antennas at +45 and -45 can satisfy the requirement of intermodulation for antenna spacing (> 30dB), so the space spacing between the dual-polarized antennas only needs 20-30cm; in addition, the dual-polarized The advantage of antenna is that the use of dual-polarized antenna in mobile communication network can reduce call loss, reduce interference and improve the quality of service of the whole network as well as the use of electrically tuned antenna. If the dual-polarized antenna is used, because the installation requirement of the dual-polarized antenna is not high, land acquisition and tower construction are not needed, only a 20 cm diameter iron pillar is needed, and the dual-polarized antenna is fixed on the iron pillar in the corresponding coverage direction, thus saving capital investment, making the layout of the base station more reasonable, and the selection of the base station location easier.

Difference between dual-polarized antenna and traditional antenna

Compared with the traditional single polarization antenna, the dual polarization antenna has the advantages of saving the number of antennas, reducing the investment in infrastructure, low site requirements and high receiving diversity gain.

Electronic tilt technology has higher accuracy than mechanical tilt technology. At the same time, adjustable electronic tilt technology can monitor and adjust wireless network coverage in real time, make wireless network more fine, effectively control wireless coverage, strengthen the signal of service community, and reduce the same frequency interference.

Therefore, in the future application of antenna technology, dual-polarized antenna and adjustable electronic dipping technology should be used as far as possible in high traffic areas such as dense base stations. Traditional Single-polarized antenna and mechanical dipping technology can still be used in low traffic areas such as edges and suburbs, non-dense base stations and areas requiring only coverage.

Vertical Directional Graph Downward Tilt Technology of Antenna

In order to limit the coverage of the service cell and reduce the interference to other co-frequency cells, antenna vertical dip pattern is an effective antenna technology. Its function can make the coverage area of the cell smaller, strengthen the signal intensity in the coverage area, increase the anti-interference ability of the same frequency, at the same time reduce the gain of the antenna in the direction of interference, and reduce the interference of other same frequency cells. Choosing the appropriate downdip angle can make the gain decay between the antenna to the cell boundary and the ray from the antenna to the interfered cell boundary in the vertical direction. The largest part of the variation is subtracted, so that the co-frequency interference of the interfered cell is minimized. Usually, mechanical dip and electronic dip are used to realize vertical dip of antenna.

(1) Mechanical dip is a physically inclined antenna. Although the same frequency interference can be reduced by using this technology, its construction and maintenance are very troublesome due to the physical downdip, and the accuracy of adjusting the dip angle is low (step-by-step accuracy is 1 degree). In addition, because the dip angle is the theoretical value of the simulation software, there is a certain deviation from the theoretical optimum value. In network adjustment, the base station system must be shut down first, the adjustment effect can not be monitored at the same time in the adjustment antenna, and fine adjustment of the network can not be carried out.

(2) Electron dip is to change the phase of the dipole of the collinear array antenna, to change the magnitude of the vertical component and the horizontal component, to change the field strength of the composite component, and to make the vertical directional pattern of the antenna dip down. Because the field intensity in all directions of the antenna increases and decreases at the same time, the antenna pattern changes little after changing the dip angle, which shortens the coverage distance in the direction of the main lobe, and at the same time reduces the coverage area of the whole pattern in the sector of the service cell without interference. The adjustable electronic dip antenna allows the system to adjust the vertical dip angle without shutdown. It can monitor the effect of the adjustment in real time, and the step precision of the adjustment dip angle is also high (0.1 degrees). Therefore, the network can be fine adjusted.

After the antenna tilts down, the signal intensity decreases due to the deviation of the cover edge from the main lobe of the antenna, which can be compensated by reasonably increasing the power of the transmitter.