Definition of BAS
In the cellular mobile communication system, the antenna is the converter between the circuit signal of the communication equipment and the electromagnetic wave radiated by space, and is the bridgehead of space wireless communication, so the base station antenna is an important part of the mobile communication system, and its characteristics directly affect the overall performance of the entire wireless network. The development of mobile communication base station antennas has mainly gone through the processes of omnidirectional antennas, directional single-polarization antennas, directional dual-polarization antennas, ESC single-polarization antennas, ESC dual-polarization antennas, dual-band ESC dual-polarization to multi-frequency dual-polarization antennas, as well as MIMO antennas and active antennas.
At present, almost different telecom operators need different types of antennas to meet their network construction requirements, and the price is still the main reference factor for each telecom operator to select antennas, but the excessive reduction of price is bound to affect the antenna performance to a certain extent. Second, it is increasingly difficult for operators to select sites when building networks. How to improve the cost performance of base station antennas and better cope with the increasing difficulty of site selection is the subsequent development trend of the mobile communication base station market. In terms of technology evolution, with the emergence of a new generation of wireless communication system LTE, how to reasonably balance the performance and price of base station antennas, and design active antennas with intelligent beamforming functions and system integration functions is the fundamental direction of its technological evolution.
The market demand development trend of mobile communication antennas.
uBroadband
With the scarcity of site resources, the base station antenna should be suitable for various environmental places; Due to people's increasing attention to visual and electromagnetic pollution, the camouflage and beautification of base station antennas have become an indispensable means. Due to people's requirements for high-quality and refined network optimization, a variety of new application schemes for base station antennas have been promoted. Due to the scarcity of site resources, the problem of multi-system co-station and multi-system co-antenna has been raised accordingly, and the broadband of base station antennas is proposed in this context. The wideband of antennas makes it possible for multiple systems to share stations and multiple systems to share antennas, which also effectively alleviates the problem of difficult site resource selection for operators. Secondly, the cost of antennas can be effectively reduced through multi-system common antennas, which is also in line with the needs of operators to continuously reduce antenna prices.
uMulti-banding
The increase in new frequency bands for wireless communication systems is driving the demand for multi-band antennas. Multi-band antennas can be divided into two-band, three-band, four-band, and five-band, etc. The use of multi-band antennas can not only meet the requirements of antenna operators to expand new applications and meet the requirements of compatibility with future new technologies, but also meet the needs of different antenna operators for multi-system co-station and multi-system co-antenna in combination with broadband. Multi-band antennas increase the weight and windward area of the antenna to a certain extent, so how to design a multi-band antenna with a lighter and smaller wind load is an important direction for the development of multi-band antennas.
uMiniaturization
The need for easy installation of antennas, the need for green site selection of operators, and the need for antennas to be integrated are the powerful driving forces for the miniaturization of antennas for mobile communication base stations. Multi-band broadband base station antennas meet the needs of multi-system co-station and multi-system co-antennas, but the weight and wind load of the antenna itself put forward requirements for the miniaturization of the antenna. Through the small size and low parabolic design of the antenna, the weight of the antenna can be effectively reduced, making it easy to install and maintain. Secondly, by reducing the wind load, the influence of environmental factors on network coverage can be reduced. In addition, through the miniaturization design of the antenna, it can meet the construction requirements of more operators with multiple systems and more systems with common antennas. Finally, the integrated design with the wireless base station can effectively reduce the feeder loss, improve the system capacity, and improve the system performance.
How to use active antennas and their advantages
According to the use mode of array antenna and the trend of technology evolution, the development of active antenna is mainly divided into three stages.
The first stage is a conventional single beam, that is, we can flexibly change the antenna gain by changing the number of slot array elements; Secondly, the amplitude and phase of the array unit are flexibly changed through electronic switches, so as to flexibly and dynamically change the vertical plane downtilt angle of the beam, so as to finally realize the dynamic change of the coverage cell range and the dynamic change of system capacity.
The second stage is the first stage of self-adaptation, which can not only flexibly change the number of slot oscillator units, but also dynamically change the array gain compared with the conventional single-beam use mode. Secondly, it controls the electronic switch of the feed network through digital signals, and generates two beams in the vertical plane, which are used for the user's upstream and downlink respectively, so for each user, the upstream and downstream power control can be used to respond to the beam gain and position to reduce the interference in the station. Through the actual simulation test, it is found that when the difference between the direction of the main beam of the uplink and downlink beams is about 5°, the distinction between the inner and outer beams can be 7~8dB, so as to effectively improve the peak rate of each user and the data transmission capacity of the whole site.
The third stage is the adaptive stage, which controls the electronic switch of the feed network of the array unit through the digital signal, which can not only realize the dynamic change of the vertical beam, but also realize the dynamic scanning of the horizontal beam. At this stage, the antenna array should be a planar array, and the core technology of the system is the beamforming algorithm. At this stage, the active antenna needs two kinds of beams, namely the broadcast beam representing the cell coverage area and the service beam applied to user communication, and the broadcast beam width and down-dip angle can be flexibly changed through electronic switch control, so the cell coverage can be dynamically changed to realize the adaptive change of system capacity; The second is the service beam obtained through the shaping algorithm and used for user communication. In specific use, the system detects the user's direction, and obtains the amplitude and phase of each array unit through a powerful shaping beam algorithm. Through the digital electronic switch, the corresponding excitation coefficient of each array unit is fed to realize that the beam is aligned with the user's communication direction, and the antenna pattern zero trap or lower power pattern gain is formed in the direction of the interference signal, so as to achieve the purpose of increasing the gain and suppressing interference, so as to effectively improve the user's communication signal-to-noise ratio and improve the system capacity. In the actual use process, these three use methods can be flexibly selected according to the environmental characteristics to achieve a comprehensive balance between cost and performance.
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