The TD-SCDMA smart antennas currently used in the existing network have single-polarized smart antennas, dual-polarized smart antennas, AEF ultra-wideband dual-polarized smart antennas, AF / AE 2-in-1 smart antennas, etc. With the continuous development and improvement of technology and applications, smart antennas will develop and advance in the direction of electric modulation, integration, and miniaturization in the future. In 4G, the combination of smart antenna technology and MIMO technology can also be considered, so that the communication terminal can achieve reliable transmission at a higher moving speed, and further improve the performance of the communication system.
Trend 1: Combining with MIMO technology
MIMO technology is a key technology in 4G, which can greatly increase the capacity of the wireless communication system and effectively improve the performance of the wireless communication system. It is very suitable for the requirements of high-speed services in future mobile communication systems.
Both smart antennas and MIMO are technologies in a multi-antenna system, and both have common features and significant differences: smart antennas are processing technologies that use array antennas to capture and combine signals only at one end of the wireless link; while MIMO is in the wireless chain Both ends of the road use a multi-element antenna array, a technology that combines transmit diversity and receive diversity. The principle of the smart antenna is to use the complete correlation between the signals reaching the antenna array to form an antenna pattern, use the phase relationship of the signal to overcome multipath interference, and realize the directional transmission and reception of the signal; in MIMO, the antenna transmits and receives signals in all directions And, the signals arriving at the antenna array must be independent of each other. Use multiple antennas to receive the signals to overcome the deep fading of the signals reaching the receiver and increase the diversity gain.
Smart antenna technology can form beams with concentrated energy, enhance useful signals and reduce interference, while MIMO technology can make full use of multipath information to increase system capacity. If you combine the two and make full use of the gains brought by the two technologies, the system performance and capacity will be greatly improved. Therefore, fully combining the advantages of MIMO technology and smart antenna technology to further develop airspace resources to enable communication terminals to achieve reliable transmission at higher mobile speeds has become one of the inevitable trends of smart antennas in the future.
Trend 2: Integrated smart antenna
At present, the dual-polarized smart antennas used in the existing network need to be additionally connected to the RRU device through 9 upper jumpers, 8 of which are connected to the antenna RF channel, and 1 is the calibration line of the smart antenna. This way of connecting the smart antenna and the RRU split by cable has some unavoidable shortcomings. For example, the 9 upper jumpers need to be waterproofed. The construction of a large number of waterproof joints brings great inconvenience to the project, making At the same time, it is difficult to install and reduces the stability of the equipment; the cable connection between the antenna and the RRU equipment also greatly reduces the outdoor appearance of the base station, the site selection and coordination are difficult, and the surrounding residents have a high level of resistance; install the RRU and antenna separately, It is time-consuming and complicated to install; the eight antenna ports need to have good amplitude and phase consistency in order to obtain accurate results in the synthesis of the directional pattern of the smart antenna and in the calibration. In practical applications, the amplitude and phase consistency of the 9 upper jumpers and the stability and reliability in long-term outdoor applications will be difficult to guarantee.
The integrated smart antenna is a smart antenna that integrates the antenna and the RRU. This type of antenna is based on the ordinary dual-polarized antenna and the external structure is adjusted accordingly. In terms of electrical performance and electrical performance testing, it is the same as the ordinary one. The dual-polarized antenna is consistent.
Considering the introduction of outdoor F and E frequency bands, integrated smart antennas will surely board the stage of TD-SCDMA network construction and become one of the important trends in the development of smart antennas.
Trend 3: ESC smart antenna
At present, the smart antennas used in the existing network all use a combination of preset downtilt and mechanical downtilt to adjust the downtilt angle of the antenna. Although this method can also meet the coverage requirements, it also exposes some shortcomings that cannot be overcome by mechanical downtilt adjustment in engineering applications. For example, it is difficult to adjust the downtilt angle. In the network optimization project, it requires a lot of human resources and adjustment. Low efficiency; due to the use of mechanical downtilt, when the station is in the concealment project, the concealed cover needs to reserve a large space for adjusting the downtilt angle, resulting in a large volume of the concealed project; the horizontal plane coverage is distorted when the angle is down, and accompanied by cross pole Polarization and main polarization characteristics become worse, the front-to-back ratio of the level is inconsistent with the trend when there is no downturn, etc.
Because of these insurmountable shortcomings of conventional smart antennas, the development and application of ESC smart antennas will inevitably become one of the important trends in the future development of TD-SCDMA smart antennas. ESC smart antenna has the following advantages:
Continuous dynamic adjustment of beam downtilt angle can be achieved. The network optimization and dynamic real-time adjustment do not require closed stations, and can balance the contradictions of coverage, capacity, interference and other aspects in time;
Vertically installed on the structure, no need to consider the reserved space for downward tilt, the installation parts are simple and reliable, and easy to beautify;
The monitoring database stores the adjustment data and historical data of antenna beams at each site, which is convenient for combining remote monitoring analysis and optimizing network coverage.
Trend 4: Medium Smart Antenna
For base station antennas, miniaturized antennas have incomparable advantages: not only can reduce mechanical load, facilitate antenna installation, but also save valuable sky resources, providing more convenient conditions for multi-system antennas to co-site, in addition It is also very beneficial to antenna beautification and concealment projects. Although the size of the current dual-polarized smart antenna has been reduced by about half of the original smart antenna size, it cannot be called a miniaturized antenna. The development and application of small-sized smart antennas is still one of the future development directions of smart antennas.
Since the propagation characteristics of electromagnetic waves are different in different media, the presence of the medium will affect the propagation of electromagnetic waves. Using this characteristic, low-loss high-frequency media is used as a filler material, combined with an appropriate antenna structure, in selecting the appropriate shape and dielectric constant In the case of the feeding method, the dielectric resonator can be used as an antenna. A major advantage of dielectric antennas is that the size of the antenna can be greatly reduced without changing the performance of the antenna.
A dielectric smart antenna is a smart antenna with a small geometric size manufactured by combining a dielectric antenna and a smart antenna. The smart antenna used in the TD-SCDMA system is an antenna array composed of multiple antenna elements. The use of dielectric materials can not only reduce the size of a single antenna element, but also reduce the spacing between the antenna elements, thereby reducing the overall smart antenna. size. The miniaturized dielectric smart antenna not only reduces the size of the antenna, but also reduces the cost, facilitates actual engineering installation, reduces the impact on the environment, and has a strong practical operability.
In recent years, the development of dielectric microwave devices driven by the miniaturization of microwave systems has been widely used in the wireless field. At the same time, the application of ordinary dielectric antennas, especially microstrip dielectric antennas, has also made considerable progress . The application technology of the dielectric antenna is mature and reliable, and it also plays a good role in the future introduction of the dielectric smart antenna.
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