At present, 5G mobile communication has been initially commercialized. On the one hand, due to the compatible use of 2G, 3G, 4G and 5G systems, the base station antennas need to be used for all the above systems, which aggravates the contradiction between the huge number of base station antennas and the increasingly tense location resources. On the other hand, in order to achieve efficient coverage of 5G signal, 5G base station antenna system adopts large-scale MIMO array, which needs to arrange hundreds of antenna elements in limited space, which will inevitably lead to the increase of base station operation cost. In order to reduce the number of base stations and reduce the operating costs of base stations, an effective method in the industry is to use multi-band and multi-array common-aperture base station antennas, that is, through the compact array layout, the antenna arrays of 2G, 3G, 4G and 5G bands are integrated, which shares the same reflector and the same antenna radome. This method realizes the signal coverage and communication of multiple network systems, and can make full use of the original base station location resources. However, the following problem is that the antenna array with multiple bands is placed in a limited space, which is bound to cause serious electromagnetic interference.
Challenges in EMC of 5G Base Station Antenna
1. Coupling Interference Between Co-frequency Antenna Elements
The large-scale MIMO array used in 5G base station antenna can effectively improve the communication capacity. At the same time, combined with multi-beam technology, the effective coverage of information can be achieved. However, the array units with smaller spacing will cause strong co-frequency coupling interference, resulting in the mismatch of antenna array, the distortion of the radiation pattern, the deterioration of isolation between units, and the reduction of the beam scanning ability of the array.
An effective decoupling scheme is to add metal clapboard or introduce electromagnetic band gap between the co-frequency units to reduce the coupling interference between the co-frequency antenna elements. The basic principle of this scheme is actually the neutralization-line technique, that is to introduce another coupling path artificially in the coupling area, so that the signal on the path can just offset the original coupling signal and play a neutralizing role. However, the difficulty of neutralization-line technique lies in two aspects, one is the realization of broadband, the other is to keep the antenna radiation pattern unchanged.
（Translated from Microwave RF network WeChat APP）
(To be continued)