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Analysis: 5g base station filter

Release date:2021-12-28Author source:KinghelmViews:223

The filter is the core RF device of the base station. The filter filters the electromagnetic wave signal and only allows the required signal to pass through. The main purpose is to solve the interference problem between different frequency bands and different forms of wireless communication systems.At present, the three main types of filters are metal coaxial cavity filter, metal cavity ceramic dielectric resonant rod filter and ceramic dielectric waveguide filter. The raw materials of the latter two involve ceramic media.In the 3G / 4G era, metal coaxial cavity filters are mainly used.



technological process

The process of high temperature sintering is: RF / structural design, dielectric powder manufacturing, spray granulation, pressing, sintering, grinding, metallization, electrode making and debugging. The core manufacturing process mainly includes four parts: powder formulation, pressing and sintering, gold forming and debugging.

technological innovation

The shape of 3G to 4G filters has little change, and the mainstream product is metal cavity filter. The application of massive MIMO technology and active antenna in 5g era drives the miniaturization and lightweight of filter. The filter industry is facing technological upgrading, and the metal cavity is evolving to ceramic dielectric filter. Huawei is the most radical in promoting the application of pure dielectric waveguide filters, and other main equipment manufacturers mainly focus on semi-dielectric or miniaturized metal filters.


      Key links in the production process of ceramic dielectric filter  

The technical difficulty of ceramic filter production lies in consistency. The formulation of ceramic powder materials, production automation and commissioning yield and efficiency are the difficulties of filter production.

Powder preparation: self owned formula is one of the competitiveness of enterprises.Ceramic powder formulation is the key factor to determine the performance of the filter. Only with a good material formulation can we obtain the corresponding high-Q dielectric ceramics. Unreasonable acid-base control, impurities and other factors will damage the powder quality.

Dry press molding: the autonomy of powder dry press molding equipment and production process are one of the core competitiveness.

The dry pressing process is to put the granulated powder into the mold, and finally rearrange and deform it to be compacted to form a ceramic plain embryo with certain strength and shape. The influencing factors mainly include: powder properties, selection of binder and lubricant, die design, pressing force in the pressing process, pressing mode, acceleration speed and holding time.

Sintering: the autonomy of sintering furnace and production process are one of the core competitiveness.Under the action of high temperature, the embryo finally forms a hard polycrystalline sintered body with a certain microstructure. Sintering process determines the grain size and density of ceramics, and then affects the mechanical strength and polarization of ceramics. The improvement of process can significantly affect the performance of products.

      Key links in the production process of ceramic dielectric filter  

The technical difficulty of ceramic filter production lies in consistency. The formulation of ceramic powder materials, production automation and commissioning yield and efficiency are the difficulties of filter production.

CNC processing: manufacturers with mature production technology can skip the CNC processing link and greatly improve the production time.CNC machining is to grind with CNC machine tool to accurately the dimensional accuracy of ceramic medium body.

Metallization:Chemical plating, spraying, sputtering, screen printing and other processes are used to coat the silver layer on the ceramic medium substrate. After silver is burned in the silver oven, the silver coating can be adjusted by laser equipment.

Commissioning:The traditional cavity filter is debugged by adjusting the resonant rod, mainly including return loss parameters, insertion loss parameters, out of band suppression parameters and so on.

The debugging of ceramic filter can only be carried out through grinding. Due to the irreversibility of ceramic grinding, product debugging is the key link affecting product yield and production efficiency.

         Ceramic dielectric filters have many advantages in 5g applications  

Ceramic dielectric filter has advantages in miniaturization, lightweight, low loss, temperature stability and cost performance.

During the 5g period, the amount of filter increases exponentially, which puts forward higher requirements for device size, weight, heating performance and price.The weight of 4G RRU is between 13-20kg and 5gaau is between 38-47kg, which poses a great challenge to the bearing of the sky.

The quality factor Q of ceramic medium is high, the relative dielectric constant is high and the loss is small.According to the propagation characteristics of electromagnetic wave, when the electromagnetic wave enters the medium with low dielectric constant from the medium with high dielectric constant, it will emit and refract on the dielectric interface. When the incident angle is greater than or equal to the critical angle, the electromagnetic wave will be totally reflected. The higher the dielectric constant of the medium, the smaller the critical angle. It is easy to form a magnetic wall on the surface of the medium. The energy of the electromagnetic field is concentrated in the resonant cavity and the radiation loss is small. The loss of the medium itself determines the Q value of the resonator, q = 1 / tan δ ( δ Is the loss angle), the higher the Q value, the easier it is to maintain the electromagnetic oscillation.

The relative dielectric constant of ceramic medium can be up to more than 90, which can greatly reduce the volume and quality of the filter without reducing the performance of the filter.The size of the filter is related to the resonant frequency and the relative dielectric constant of the material. The higher the resonant frequency and the relative dielectric constant, the smaller the device size. The geometric size of the dielectric filter is half of the waveguide wavelength.

Ceramic dielectric materials are lighter and cheaper than metal materials.

         Base station filter industry barriers  

High industry barriers:

Certification barriers.If the supplier passes the certification of the downstream communication main equipment supplier and supplies in batches, it needs to be inspected and reviewed by the communication main equipment supplier for a long time. Once the supplier passes the certification of the main equipment supplier, the main equipment supplier will not easily consider replacement, but it may be eliminated if it fails to keep up with the technical innovation. (high requirements for independent R & D capability and rapid response capability)

technology barrier.From design to manufacturing, filters need to master key technologies in various disciplines. Suppliers need to accumulate for a long time to produce cost-effective products.

Customer trust.In the era of 5g and the Internet of things, higher requirements and guarantees are put forward for the reliability and security of the Internet of things. System integrators are more important to the ability certification and trust of suppliers, and will carefully select new entrants.

Financial barriers.The production equipment of the filter includes mold processing equipment, die casting machine, CNC machining center, network analyzer and other high-value equipment, and more funds are invested in the early stage of mass production. Sufficient funds are also needed to deal with the payment credit period of customers.


Base station filter industry market space


         Challenges and opportunities of base station filter in 5g Era  

Compared with the structural changes of the base station in the 4G era, 5g brings growth space to the RF end of the base station antenna

1) Antenna and RF integrated AAU (antenna RRU = AAU);

2) The BBU is divided into Cu (centralized unit) and Du (distributed unit);

3) The wide application of massive MIMO antenna requires a significant increase in the number of RF channels (from the average two transmitter and two receiver in the 4G era to the mainstream 64 transmitter and 64 receiver in the future, and 32 transmitter and 32 receiver or 16 transmitter and 16 receiver)

In 5g era, the filter technology is innovated, and the gross profit margin of new products is high in the early stage



         Capacity calculation of 5g macro base station  

The transmission of electromagnetic wave in space follows the following formula:

Transmission loss = 20logf 20logd 32.4

Where f is the frequency of electromagnetic wave and D is the transmission distance.

Core assumptions:

(1) 4G frequency is calculated as 2.4GHz and 5g frequency is calculated as 3.5GHz. (2) the base station is covered in the form of cell, which is approximately circular to simulate (3) 5g signal to achieve the same coverage of 4G.

Main conclusions:

(1) The coverage distance of 4G base stations is 1.5 times that of 5g base stations

(2) The coverage area of 4G base stations is 2.1 times that of 5g base stations

(3) With the same coverage of 4G, the number of 5g base stations is twice that of 4G

         Detailed estimation of base station filter Market Space: both volume and price rise  

Assumption: Based on the prediction of Guosen Securities on the number of 5g base stations in the next few years.

2018 is the sixth year of 4G construction. The peak of 4G construction occurred in 2014-2016, with nearly one million base stations built every year. According to the total caliber of the three operators, the number of 4G base stations exceeded 4.5 million in 2018.

2019 is the first year of 5g construction. It is expected to reach the peak from 2021 to 2023. More than 1 million 5g base stations will be added every year, and the investment on the base station side alone will reach 200-300 billion yuan.

Market space estimation:

Market space of filter in 5g era = number of base stations X amount of single base station filter (i.e. number of channels of single base station) x price of single channel filter

Market space of filter in 4G era = number of base stations x price of filter used by single base station (number of days x corresponding value of single day)

Number of base stations:The number of 4G base stations in China is about 4.5 million, and the number of global 4G base stations is about twice that in China, about 9 million. According to 1.2 times conservative calculation, the total number of 5g domestic base stations is about 5.4 million (construction period 2019-2025), and the number of global base stations in the same period is about 10.8 million. At 1.5 times, the total number of 5g domestic base stations is about 6.75 million, and the number of global base stations in the same period is about 13.5 million.

4G filter Market Space:There are three antennas in a single base station, and the value of the filter corresponding to each antenna is currently 800-1000 yuan. Assuming that the annual price reduction in the early stage is 20%, it can be calculated that the domestic 4G filter market space is about 21.483 billion yuan and the global market space is about 42.966 billion yuan.

5g filter Market Space:The mainstream scheme of 5g high-capacity hotspot scenario is 64t64r, that is, 64 channels, so a base station has 3 antennas and 192 channels. It is estimated that the current price is about 50 yuan / single channel, and the price is expected to decline further with the progress of process level and commissioning level. It is assumed that the unit price of 5g filter will decrease by 10% every year during the supply period of 5g filter. Calculated, the domestic 5g filter market space is 37.221 billion yuan (1.73 times that of 4G), and the global market is about 73.550 billion yuan (1.71 times that of 4G).

          Detailed estimation of base station filter Market Space: both volume and price rise    

Market space estimation

Upstream and downstream analysis of base station filter industry chain


Industrial chain analysis:

The upstream of the traditional metal RF filter industry is the supplier of RF metal components and structural parts, and the industry concentration is low. The upstream raw materials in 5g era have changed from metal materials to ceramic powder. The ceramic powder formula directly affects the performance of the filter. Therefore, its own mature formula is one of the core competitiveness of filter manufacturers and helps to reduce costs.

Before 2000, the core production technology of microwave ceramics was mainly in the hands of Japan and the United States. At present, domestic manufacturers have mastered the production technology of ceramic powder, which is still in its infancy.

          Base station filter industry chain analysis    

Industrial chain analysis:

The downstream of the industry is the communication equipment integrator, and the products are integrated by the main equipment supplier and delivered to the operator. The operator capex determines the development progress of the industry, and the main equipment supplier affects the competition pattern of the upstream industry.

From the perspective of investment cycle, each generation of mobile communication network will be commercialized iteratively in a 10-year cycle. China's 5g is expected to be commercialized on a large scale in 2020. At present, it is at the end of 4G and gradually transition to 5g. 4G and 5g are expected to coexist for a period of time. Judging from the pace of China's 5g infrastructure construction, 2019 is expected to be the climbing stage of industry capacity, 2020 is the starting point of industry investment, and 2021-2023 is the peak of 5g investment and construction.

From the ecological pattern of main equipment suppliers, each main equipment supplier cultivates its own supplier system according to its own technical route, and selects 3-4 core suppliers in each subdivided field of the communication equipment industry, which determines the competition pattern of the upstream filter industry. With the technological innovation and the survival of the fittest, when a new round of communication cycle comes, the competition pattern of the upstream supplier industry is facing a reshuffle.

Construction of operators

Internationally, the United States, South Korea, Switzerland and the United Kingdom have announced commercial use. Among them, South Korea is expected to build 90000 5g base stations by the end of this year.

Domestically, China Mobile will build more than 50000 5g base stations in 2019, 5g commercial in more than 50 cities, and 5g commercial in cities above prefecture level in 2020; China Unicom has opened 5g pilot network in 40 cities; China Telecom has built 5g pilot network in 17 pilot cities and rapidly promoted it to 40 cities.


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