Excerpted from: Semiconductor Industry Observer
5G has set higher requirements for equipment performance and power efficiency, especially on the base station side. The increasing number of base stations and the rising cost of individual base stations will bring significant market growth. According to cellular communication theory calculations, to achieve the same coverage, it is estimated that the number of 5G macro base stations in China will reach about 5 million. In 2021, the global 5G macro base station PA and filter market will reach 24.31 billion yuan, with an average annual compound growth rate (CAGR) of 162.31%. In 2021, the global 4G and 5G small cell RF device market will reach 2.154 billion yuan, with a CAGR of 140.61%.
With the increasing use of multi-antenna MIMO technology in base stations, more demands are placed on PAs. It is expected that by 2022, the RF semiconductor market for 4G/5G infrastructure will reach 1.6 billion US dollars, among which the CAGR of MIMO PA will reach 135%, and the CAGR of RF front-end modules will reach 119%.
Compared with 4G, the number of PAs used in 5G base stations will double. A 4G base station adopts a 4T4R solution, with 12 corresponding RF PAs for three sectors. In 5G base stations, it is expected that 64T64R will become the mainstream solution, with a corresponding PA demand of up to 192.
Power Consumption Issues to be Resolved
Although the prospects for 5G are promising, the related technologies have not yet reached a mature level, especially in terms of power consumption. This issue exists both in base stations and mobile phones, and it is also one of the important reasons why Apple has not yet launched a 5G phone.
Especially for base stations, the power consumption is significantly higher than that of 4G. Among all power-consuming chips and components, the PA is a major consumer. Since the power of RF signals is very low, they need to be amplified by the PA to obtain sufficient RF power before being fed to the antenna and transmitted. Therefore, the PA is an important component of the base station transmission system. At the same time, the PA is also the most power-consuming and low-efficiency component. Statistics show that about half of the base station power consumption is used by the PA.
However, there is a very clear difference in power consumption between macro base stations and small cells: compared with macro base stations, small cells have a smaller coverage area, lower transmission power, smaller PA nonlinear distortion, and a smaller proportion of PA power consumption. They may not even need DPD and other technologies for predistortion processing. Therefore, corresponding to the different base stations, especially the needs of 5G base stations, there are more product routes for PA, and more business opportunities in the future.
GaN Replaces LDMOS
The PA market for base stations is huge, but its performance and power efficiency issues are urgent to be solved. Against this backdrop, the replacement of traditional processes by new process technologies has long been on the agenda.
The current PA market, including those for base stations and mobile phones, mainly uses traditional LDMOS, GaAs, and emerging GaN manufacturing processes. In base stations, the traditional LDMOS process is used more, but LDMOS technology is suitable for low-frequency bands and has limitations in high-frequency applications. To meet the 5G network's demands for performance and power efficiency, GaN is increasingly used and can better adapt to large-scale MIMO.
GaN has excellent high power density and high-frequency characteristics. GaAs, with microwave frequencies and operating voltages of 5V to 7V, has been widely used in PAs for many years. Silicon-based LDMOS technology, with an operating voltage of 28V, has been used in the telecommunications field for many years, but it mainly functions at frequencies below 4GHz and is not widely used in broadband applications. In comparison, GaN has an operating voltage of 28V to 50V, with higher power density and cutoff frequency, and can achieve highly integrated solutions in MIMO applications.
In macro base station PA applications, GaN is gradually replacing LDMOS with its advantages of high frequency and high output power; in small cells, the GaAs process will still be the mainstream for a period in the future, because of its advantages in reliability and cost-effectiveness. However, as the cost of GaN devices decreases and the technology improves, GaN PA is expected to gradually expand in small cell applications.
In mobile phones, the RF front-end PA is still mainly based on the GaAs process, and there is no short-term opportunity for GaN, mainly due to cost and high voltage characteristics, which are not acceptable in mobile phones.
In summary, it is likely that most macro base station applications below 6GHz will adopt PA based on GaN process. The 5G network uses higher frequency bands, and its penetration and coverage will be worse than 4G. Therefore, small cells will play an important role in 5G network construction. However, since small cells do not require such high power, existing technologies such as GaAs still have their advantages. The traditional LDMOS process will gradually reduce its share in the base station PA market and may exit the historical stage in the near future.
