Suzhou Mette Technology share: The changes of 5G base station filters in recent years

 In the 3G/4G period, the base station consists of three parts: baseband processing unit BBU, RF processing unit RRU and antenna feed system. 

 In the 5G era, the three major components of the base station have undergone significant changes :

(1) the BBU is split into CU-DU two-stage architecture; 

(2)RRU and large-scale array antenna merged to form an active antenna AAU;

 (3) Some physical layer functions of the original BBU are placed in the AAU. 

The investment impact of the above three changes has been explained in detail in series four and five, and this issue mainly analyzes the technological upgrading trend of filters as one of the key RF devices in the 5G era, as well as potential investment targets worthy of attention. 

 In the 3G/4G era, the metal coaxial cavity filter is the mainstream choice in the market: the base station filter is a key component of the radio frequency system, the main working principle is to make the specific frequency components in the sent and received signal through, and greatly attenuation of other frequency components. The filter used in traditional applications is generally realized by a metal coaxial cavity, which oscillates through electromagnetic waves of different frequencies in the coaxial cavity filter, and the electromagnetic waves reaching the resonant frequency of the filter are preserved, and the electromagnetic waves of the remaining frequencies are dissipated in the oscillation. In the 3G/4G era, metal coaxial cavities have become the mainstream choice in the market with lower costs and more mature processes. In response to the increasing complexity of wireless environmental interference, ceramic dielectric resonant filters have developed rapidly: with the development of mobile communication networks, the wireless frequency band has become very dense, resulting in metal cavity filters can not achieve high suppression system compatibility problems, and the use of ceramic dielectric materials to make cavity filters can solve the above problems. Compared with the traditional metal cavity resonators, the ceramic dielectric resonant filter has the characteristics of high rejection, low insertion loss, good temperature drift, and the power capacity and passive intermodulation performance have been greatly improved. Ceramic dielectric resonant filter represents the development direction of high-end RF devices, with its excellent performance, it has a broader application space in the field of mobile communication. New changes in base station filters in the 5G era - ceramic dielectric filters: In the 5G era, limited by MassiveMIMO's requirements for large-scale antenna integration, filters need to be more miniaturized and integrated. The electromagnetic wave resonance in the ceramic dielectric filter occurs inside the dielectric material, there is no metal cavity, and the volume is smaller than the above two filters, while having the advantages of the ceramic dielectric resonance filter, and the cost will be lower once the mass production is achieved. We believe that ceramic dielectric filters are expected to become the mainstream choice for low and medium frequency bands in the 5G era.