Unveiling the secrets of RF chips, the king of chips in the 5G era

Latest update time：2020-06-11

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What is a RF chip?

Radio Frequency (RF) refers to the electromagnetic frequency that can be radiated into space, ranging from 300kHz to 300GHz. RF is the abbreviation of a high-frequency alternating electromagnetic wave.

A radio frequency chip is a chip that can convert radio frequency signals and digital signals. Specifically, it includes an RF transceiver, a power amplifier (PA), a low noise amplifier (LNA), a filter, a radio frequency switch (Switch), an antenna tuning switch (Tuner), etc.

▲ Logical relationship diagram of mobile phone RF chip

RF front-end devices are all made by semiconductor technology. Power amplifiers and low-noise amplifiers used in mobile phones are mainly based on GaN, GaAs, SOI, SiGe, and Si (high-power amplifiers used in base stations are mainly based on GaAs and GaN). The main types of filters are SAW and BAW, both of which use piezoelectric materials as substrates. RF switches are mainly based on CMOS, Si, GaAs, and GaN materials.

▲ Process technology and application of RF front-end devices

A typical 4G mobile phone needs to support about 40 frequency bands, such as B1, B3, B5, B8, B38, B41, etc. Each frequency band needs to have one transmission channel and two reception channels. The transmission channel requires filters, power amplifiers, switches, etc., and the reception channel requires switches, low-noise amplifiers, filters and other devices.

In the 4G LTE frequency band division, there are some frequency bands with similar or overlapping frequencies, which can form shared RF front-end devices. The industry usually divides the 4G frequency band into low frequency (698~960Mhz), medium frequency (1710~2200MHz) and high frequency (2400~3800MHz). Correspondingly, the corresponding RF front-end devices can form low-frequency modules, medium-frequency modules and high-frequency modules.

▲4G mobile phone RF architecture

Since 5G has added new frequency bands, supporting the new frequency bands requires adding matching RF front-end chips.

To simplify, the RF transmission path mainly consists of PA and filter, the receiving path mainly consists of LNA and filter, and others such as RF switch, RFIC, resistor, capacitor, and inductor are all supporting components of the core chip.

▲5G mobile phone RF architecture

▲ Simplified schematic diagram

RF Chip Market

According to Yole Development data, the global mobile terminal RF front-end market size was US$15 billion in 2018 and is expected to reach US$25.8 billion in 2025, with a 7-year CAGR of 8%.

▲ RF front-end chip market space from 2018 to 2025 (billion US dollars)

▲The expansion of market space comes from the increase in the value of single machines

RF switch. The function of RF switch is to connect any one or several of the multiple RF signals through control logic to achieve the switching of different signal paths, including the switching of reception and transmission, the switching between different frequency bands, etc., so as to achieve the purpose of sharing antennas and saving terminal product costs. The main product categories of RF switch include mobile communication conduction switch, WiFi switch, antenna tuning switch, etc., which are widely used in mobile intelligent terminals such as smart phones.

Take smartphones as an example. Due to the changes in mobile communication technology, smartphones need to receive RF signals in more frequency bands. In 2011 and before, the number of frequency bands supported by smartphones did not exceed 10. With the popularization of 4G communication technology, the number of frequency bands supported by smartphones has approached 40 by 2016. The number of frequency bands supported by 5G applications will increase by more than 50, and the total number of frequency bands supported by global 2G/3G/4G/5G networks will exceed 91. Therefore, the number of RF switches in mobile smart terminals needs to be continuously increased to meet the needs of receiving and transmitting signals in different frequency bands.

According to Yole Development, the market size of discrete RF switches will grow from US$600 million in 2018 to US$900 million in 2025, with a compound annual growth rate of 5%.

▲Schematic diagram of a typical RF switch

▲ Discrete general RF switch market space from 2018 to 2025 (billion US dollars)

Antenna tuning switch (Tuner). Tuner is mainly used to match the antenna. With the popularity of full-screen phones and compact body design, the space left for antennas in smartphones is constantly limited, which leads to a decrease in the overall efficiency of the antenna system. Antenna tuning switches are needed to improve the antenna's ability to receive signals in different frequency bands. The importance and demand for antenna tuning switches are also growing. Compared with ordinary switches, antenna tuning switches have extremely high withstand voltage requirements. At the same time, on-resistance and off-capacitance have a great impact on performance, which puts forward extremely high design and process requirements for products.

4G mobile phones generally require 4 to 6 antennas, while 5G mobile phones require at least 6 to 10 antennas, and the corresponding antenna tuner needs to be more adaptable. According to Yole Development, the market size of antenna tuning switches will grow from US$500 million in 2018 to US$1.2 billion in 2025, with an average annual compound growth rate of 13%.

▲Schematic diagram of a typical tuner

▲ Tuner market space from 2018 to 2025 (billion US dollars)

Filter. The function of RF filter is to retain the signal within a specific frequency band and filter out the signal outside the specific frequency band, thereby improving the signal's anti-interference and signal-to-noise ratio. Taking the surface acoustic wave filter as an example, its working principle is: the input electrical signal is converted into a sound wave of the same frequency by the input interdigital transducer, and then converted into an electrical signal by the output interdigital transducer to achieve frequency selection.

The market for filters is driven mainly by the need for additional filtering in new communication formats. The gradual implementation of 4G and 5G frequency bands, the application support of MIMO and carrier aggregation, and the popularization of wireless technologies such as Wi-Fi, Bluetooth, and GPS have led to a rapid growth in demand for RF filters.

According to Yole Development's forecast, from 2018 to 2025, the market size of discrete RF filters and duplexers will grow from approximately US$3.1 billion to US$5.1 billion, of which filters will grow from approximately US$1.7 billion to US$2.7 billion, with a compound annual growth rate of 7%; duplexers will grow from approximately US$1 billion to US$1.6 billion, with a compound annual growth rate of 7%; the multiplexer market will have the fastest growth, growing from approximately US$100 million to US$500 million, with a compound annual growth rate of 20%.

▲Schematic diagram of RF filter

▲Filter market space from 2018 to 2025 (billion US dollars)

Low noise amplifier (LNA). The function of the low noise amplifier is to amplify the weak RF signal received by the antenna, minimize the introduction of noise, and achieve better signal, call quality and higher data transmission rate on the mobile smart terminal. According to the applicable frequency, it is divided into global satellite positioning system RF low noise amplifier, mobile communication signal RF low noise amplifier, TV signal RF low noise amplifier, FM signal RF low noise amplifier.

The working principle of the low-noise amplifier: the input RF signal is converted into voltage by the input matching network, the voltage is amplified by the amplifier, and the introduction of self-noise is minimized during the amplification process, and finally converted into an amplified power signal output through the output matching network.

As 5G becomes more and more popular, the number of antennas and RF channels in smartphones increases, and the demand for RF low-noise amplifiers increases rapidly. According to Yole Development, the market size of discrete RF low-noise amplifiers will grow from approximately US$300 million in 2018 to US$800 million in 2025, with a compound annual growth rate of 16%.

▲LNA schematic diagram

▲ LNA market space from 2018 to 2025 (billion US dollars)

Power amplifier (PA). The power amplifier (PA) is an important component of various wireless transmitters. It amplifies the power of the RF signal generated by the modulation oscillation circuit and outputs it to the antenna for radiation. The performance of the PA directly determines the communication distance, signal quality and standby time of the wireless terminal. It is also the device with the highest power consumption in the RF front end.

According to QYR Electronics Research data, from 2011 to 2018, the global RF power amplifier market size grew from US$2.533 billion to US$3.105 billion, with an average annual compound growth rate of 2.95%; it is expected that by 2023, the market size will reach US$3.571 billion. The overall growth rate of the PA market is lower than that of other RF front-end chips, mainly because the high-end 4G and 5G PA markets will continue to grow, but the 2G/3G PA market will gradually decline.

▲ PA chip pin function block diagram

▲ Annual PA market space from 2011 to 2023 (billion US dollars)

RF chips: discrete and modules. RF front-end modules integrate two or more discrete devices such as RF switches, low-noise amplifiers, filters, duplexers, power amplifiers, etc. into one module, thereby improving integration and performance and miniaturizing the volume. According to different integration methods, it can be divided into DiFEM (integrated RF switches and filters), LFEM (integrated RF switches, low-noise amplifiers and filters), FEMiD (integrated RF switches, filters and duplexers), PAMiD (integrated multi-mode multi-band PA and FEMiD) and other module combinations.

The contradiction between the increasing number of RF front-end devices and the shrinking available area of PCB boards has promoted the development of RF front-end modules. More and more discrete RF front-end chips are packaged in the same large chip through SiP technology. From the development of Broadcom, from 2007 to 2010, it was mainly discrete RF front-end devices, from 2011 to 2013, it was a single PA module, and since 2014, it has been continuously upgraded and has achieved multi-band PA module integration. At the same time, Skyworks, Qorvo, Murata, Qualcomm and other major RF front-end chip manufacturers have launched multiple categories of RF front-end module products.

RF chips: discrete and modules. According to Yole Development's statistics and forecasts, discrete devices and RF modules share the entire RF front-end market. In 2018, the RF module market reached $10.5 billion, accounting for about 70% of the total RF front-end market capacity. By 2025, the RF module market will reach $17.7 billion, with an average annual compound growth rate of 8%; in 2018, the discrete device market reached $4.5 billion, accounting for about 30% of the total RF front-end market capacity. By 2025, discrete devices will still retain a market size of $8.1 billion.

▲ Comparison of market size of discrete RF front-end chips and modules from 2018 to 2025 (million US dollars)

Receiver module (FEM). Receiver module mainly refers to the RF module that undertakes the download function, excluding PA. Taking a mobile phone as an example, the process of communicating with a base station is divided into uplink (upload) and downlink (download). When a mobile phone uploads data, the mobile phone PA needs to amplify the signal, and the base station is in a receiving state; when downloading data, the base station PA needs to amplify the signal, and the mobile phone is in a receiving state. Receiver module is mainly a combination of RF switches, filters, LNA and other chip products.

According to Yole Development data, the RF front-end receive module market space is expected to grow from US$2.5 billion in 2018 to US$2.9 billion in 2025, with a compound annual growth rate of 2%.

▲The receiving module used in Xiaomi 10

▲ Receiver module market size from 2018 to 2025 (billion US dollars)

Power amplifier module (PAM). The power amplifier module mainly refers to the RF module that is responsible for uploading signals, including PA. Taking a mobile phone as an example, the process of communicating with a base station is divided into uplink (upload) and downlink (download). When a mobile phone uploads data, the mobile phone PA needs to amplify the signal, and the base station is in a receiving state; when downloading data, the base station PA needs to amplify the signal, and the mobile phone is in a receiving state. The power amplifier module is mainly an arrangement and combination of chip products such as RF switches, filters, and PAs. Taking a certain M/HB PA module of Qorvo as an example, in a large SiP package, it contains 12 filters, 3 PAs, 1 control chip, 1 antenna switch, and 3 RF switches.

According to Yole Development data, the power amplifier module market space is expected to grow from US$6 billion in 2018 to US$10.4 billion in 2025, with an average annual compound growth rate of 8%.

▲Schematic diagram of RF filter

▲ Power amplifier module market space from 2018 to 2025 (billion US dollars)

AiP module (millimeter wave antenna module). Due to the high frequency of millimeter waves and large transmission loss, the antenna and RF front end are integrated. In a typical design, the millimeter wave antenna and millimeter wave chip are packaged together, which is called AiP (antenna-in-package) in the industry.

At present, the US 5G network is mainly promoting the construction of millimeter waves. The US version of Samsung is equipped with AiP modules to support the US 5G frequency band. It is expected that the US version of the new iPhone in 2020 will also need to be equipped with AiP modules.

According to Yole Development data, AiP modules began to generate sales in 2019, mainly in the US market. The market space is expected to reach US$1.3 billion by 2025, with a compound annual growth rate of 68%.

▲AiP module composition

▲ Filter market space from 2018 to 2025 (billion US dollars)

WiFi module. WiFi function is a must for smartphones. The latest generation standard is WiFi 6, which is fully supported by new mobile phones launched in 2020, such as Xiaomi 10, Huawei P40, and iPhone SE 2nd generation. Each standard upgrade will drive related chip innovation and value increase. With the popularization and penetration of the new WiFi 6 standard, according to Yole Development data, the WiFi module market size is expected to grow from US$2 billion in 2018 to US$3.1 billion in 2025, with an average annual compound growth rate of 6%.

▲iPhone SE motherboard, the yellow box is USI 339S00648 WiFi/Bluetooth SoC, supporting the latest WiFi 6

▲ Filter market space from 2018 to 2025 (billion US dollars)

Competitive Landscape

RF devices are essentially semiconductor devices. After the peak of 4G popularization, the growth of RF device manufacturers declined. Since 2014, RF device manufacturers have continued to acquire and merge. In 2014, TriQuint and RFMD merged to form Qorvo. In 2016, Qualcomm and TDK jointly invested to establish RF360. Avago acquired Broadcom. Traditional semiconductor chip manufacturers continue to integrate, combining their respective advantageous products through acquisitions or joint investments, seeking a stronger position in the industry chain, and striving to supply multiple categories of devices.

In general, overseas oligarchs occupy an absolute share. The global RF front-end chip market is mainly occupied by Murata, Skyworks, Broadcom, Qorvo, Qualcomm and other leading foreign companies for a long time. According to Yole Development data, in 2018, the top five RF device providers accounted for 80% of the RF front-end market share, including Murata 26%, Skyworks 21%, Broadcom 14%, Qorvo 13%, Qualcomm 7%.

International leading enterprises started earlier and have a deep foundation. They have strong leadership in technology, patents, and processes. At the same time, through a series of industrial integration, they have a complete product line and strong R&D capabilities in high-end products. On the other hand, most enterprises operate in the IDM model, have the full industrial chain capabilities of design, manufacturing, and packaging and testing, and have strong comprehensive strength.

From the disassembly of flagship models, Tuner is used the most. Referring to the disassembly information of flagship phones of various brands such as iPhone Xs, Samsung S20, Huawei P30, Xiaomi 8, OPPO Find X, in addition to the five major manufacturers of Murata, Skyworks, Broadcom, Qorvo, and Qualcomm, mainstream suppliers include Infineon, Huawei HiSilicon, Sony, ON Semiconductor, STM, NXP, etc.

Among the RF product categories, antenna tuning switches (Antenna Tuner) account for the largest proportion, reaching 33%, and others are transmitting modules (including HB PAMiD, MB PAMiD, HB/MB PAMiD, PAM), receiving modules (including FEM, switch low noise amplifier module), RF switches and LNA.

▲Distribution of flagship smartphone RF front-end chip suppliers

▲ Distribution of flagship smartphone RF front-end chips

Domestic manufacturers started late, starting from discrete. In contrast, domestic RF chip companies started late, have a weak foundation, and are mainly concentrated in the field of fabless design. Compared with international leading companies, they still lag behind in technology accumulation, industrial environment, talent training, and innovation capabilities, and there is still a big gap with manufacturers in the United States, Japan, Europe, etc.

Domestic RF chip manufacturers started with relatively mature discrete RF chips. In the window period before the widespread popularization of 5G mobile phones, they gradually replaced the imports of RF front-ends for mid- and low-end models, while accumulating module capabilities and gradually moving towards full-category supply.

▲ Filters and RF switches form FEM, and FEM plus PA form PAM, from discrete to module, step by step

Take the iPhone X as an example. It uses a Broadcom transmitter module chip, which contains multiple discrete chips inside and is packaged into a large chip through SiP. This large chip contains 2 PAs, 12 BAW filters, 2 RF switches, and a control IC. In addition, there are 10 inductors and 30 capacitors.

At present, the products provided by local RF manufacturers are mainly concentrated in discrete devices, grabbing the market share of the mid- and low-end markets, and the products provided tend to be homogenized, which leads to the decline of market prices and the reduction of industry profits. Considering the characteristics of the chip design industry, only by continuously investing in new technologies and new products and building an industrial chain with independent development capabilities and core competitiveness can the gap with international leading companies be gradually narrowed.

▲ The RF module is composed of multiple RF discrete chips

From the changes in Huawei's RF chip suppliers to see independent control. Before 2018, the main suppliers of RF chips for Huawei's P series and Mate series flagship models were Murata, Skyworks, Qorvo and Epcos. After the US sanctions in 2018, Huawei's supply chain gradually abandoned US suppliers, adopted HiSilicon's self-developed products and accelerated the introduction of domestic suppliers. In the Mate 30 mobile phone in Q4 2019, the RF chips mainly came from Murata, HiSilicon and Zhuoshengwei.

▲2015Q4~2019Q4, changes in major RF chip suppliers in Huawei’s flagship models (P and Mate series)

▲RF chip supplier for Huawei flagship phones since 2015

Every communication standard upgrade is an opportunity to increase the value of RF chips. 5G mobile phones must take into account 2/3/4G. Therefore, while retaining 2/3/4G RF chips, 5G mobile phones support RF chips in new 5G frequency bands as a new increment. Although RF chips have always been monopolized by foreign giants, domestic RF chip manufacturers started with relatively mature discrete RF chips. In the window period before the widespread popularization of 5G mobile phones, they gradually replaced the import of RF front-ends for mid- and low-end models, accumulated module capabilities, and gradually moved towards full-category supply.

Source: Zhidongxi