One article to understand the RF chip industry chain and its domestic status!
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I saw a very good article from ittbank, which explained the RF chip industry chain very clearly. I would like to share it with you.
Source: ittbank official account
▲Overview of the evolution of global RF company integration
▲Global RF front-end market growth and share
▲Market demand for filter products
A mobile phone that supports making calls, sending text messages, Internet services, and APP applications usually consists of five parts: radio frequency, baseband, power management, peripherals, and software.
Radio frequency: generally the part that sends and receives information;
Baseband: generally the information processing part;
Power management: generally refers to power saving. Since mobile phones are devices with limited energy, power management is very important.
Peripherals: generally include LCD, keyboard, case, etc.;
Software: generally includes systems, drivers, middleware, and applications.
In mobile terminals, the most important core is the RF chip and baseband chip. The RF chip is responsible for RF transmission and reception, frequency synthesis, and power amplification; the baseband chip is responsible for signal processing and protocol processing. So what is the relationship between the RF chip and the baseband chip?
1. The relationship between RF chip and baseband chip
Radio Frequency and Base Band are both direct translations from English. The earliest application of radio frequency is radio - wireless broadcasting (FM/AM), which is still the most classic application of radio frequency technology and even the radio field.
The baseband is the signal with the center point of the band at 0Hz, so the baseband is the most basic signal. Some people also call the baseband "unmodulated signal", and this concept was once correct. For example, AM is a modulated signal (no modulation is required, and the content can be read through the sound-emitting components after receiving).
But in the modern communication field, baseband signals usually refer to digitally modulated signals with the spectrum centered at 0 Hz. There is no clear concept that baseband must be analog or digital, which depends entirely on the specific implementation mechanism.
Back to the point, the baseband chip can be considered to include the modem, but it is more than just a modem, it also includes channel coding and decoding, source coding and decoding, and some signaling processing. The RF chip can be considered to be the simplest up-conversion and down-conversion of the baseband modulation signal.
Modulation is the process of modulating the signal to be transmitted onto a carrier wave according to certain rules and then sending it out through a wireless transceiver (RF Transceiver). Demodulation is the opposite process.
2. Working Principle and Circuit Analysis
Radio frequency is abbreviated as RF. Radio frequency is radio frequency current, which is a high-frequency alternating electromagnetic wave. It is the abbreviation of Radio Frequency, which means the electromagnetic frequency that can be radiated into space, and the frequency range is between 300KHz and 300GHz. Alternating current that changes less than 1000 times per second is called low-frequency current, and alternating current that changes more than 10,000 times per second is called high-frequency current, and radio frequency is such a high-frequency current. High frequency (greater than 10K); radio frequency (300K-300G) is a higher frequency band of high frequency; microwave frequency band (300M-300G) is a higher frequency band of radio frequency. Radio frequency technology is widely used in the field of wireless communications, and cable TV systems use radio frequency transmission.
RF chip refers to an electronic component that converts radio signal communication into a certain radio signal waveform and sends it out through antenna resonance. It includes power amplifier, low noise amplifier and antenna switch. The RF chip architecture consists of two parts: receiving channel and transmitting channel.
▲RF circuit block diagram
Structure and working principle of receiving circuit
When receiving, the antenna converts the electromagnetic waves sent by the base station into weak AC current signals, which are filtered and amplified at high frequency, and then sent to the intermediate frequency for demodulation to obtain the received baseband information (RXI-P, RXI-N, RXQ-P, RXQ-N); and sent to the logic audio circuit for further processing.
The key points of this circuit are: 1. Receiving circuit structure; 2. Functions and effects of each component; 3. Receiving signal flow.
1. Circuit structure
The receiving circuit is composed of antenna, antenna switch, filter, high-frequency tube (low noise amplifier), intermediate frequency integrated block (receiver demodulator), etc. Early mobile phones had primary and secondary mixing circuits, the purpose of which was to reduce the receiving frequency before demodulation (as shown in the figure below).
▲Block diagram of receiving circuit
2. Functions and effects of each component
1) Mobile phone antenna:
Structure: (as shown below)
Mobile phone antennas are divided into external and internal antennas; they are composed of an antenna base, a solenoid, and a plastic cover.
Function: a) Convert the electromagnetic waves sent by the base station into weak AC current signals when receiving. b) Convert the AC current amplified by the power amplifier into electromagnetic wave signals when transmitting.
2) Antenna switch:
Structure: (as shown below)
The mobile phone antenna switch (combiner, duplex filter) consists of four electronic switches.
Function: a) Complete the switching between receiving and transmitting; b) Complete the switching between 900M/1800M signal receiving.
The logic circuit sends out control signals (GSM-RX-EN; DCS-RX-EN; GSM-TX-EN; DCS-TX-EN) according to the working status of the mobile phone, making each path conductive, so that the receiving and transmitting signals can go their own way without interfering with each other.
Since the receiving and transmitting of a mobile phone cannot work at the same time in the same time slot (i.e., it cannot transmit when receiving and it cannot receive when transmitting), the two switches of the receiving path are removed from the new mobile phones in the later period, leaving only two transmitting switching switches; the receiving switching task is completed by the high-power tube.
3) Filter:
Structure: There are high-frequency filters and medium-frequency filters in mobile phones.
Function: Filter out other useless signals to get pure received signals. Later new mobile phones are all zero intermediate frequency mobile phones; therefore, there is no intermediate frequency filter in the mobile phone.
4) High-frequency amplifier (high-frequency amplifier, low-noise amplifier):
Structure: There are two high-frequency amplifiers in mobile phones: 900M high-frequency amplifier and 1800M high-frequency amplifier. Both are triode common emitter amplifier circuits; later new mobile phones integrate high-frequency amplifiers inside the intermediate frequency.
▲High-frequency amplifier power supply diagram
Function: a) Amplify the weak current sensed by the antenna to meet the signal amplitude requirements of the subsequent circuit. b) Complete the 900M/1800M receiving signal switching.
Principle: a) Power supply: The base bias voltages of the two 900M/1800M high-power amplifier tubes share one path, which is provided by the intermediate frequency circuit at the same time; and the collector bias voltages of the two tubes are sent out in two paths by the intermediate frequency CPU according to the reception status command of the mobile phone; its purpose is to complete the 900M/1800M reception signal switching.
Principle: b) After filtering out other clutter, the pure 935M-960M receiving signal is coupled by a capacitor and sent to the corresponding high-frequency tube for amplification, and then coupled by a capacitor and sent to the intermediate frequency for the next level of processing.
5) Intermediate frequency (RF interface, RF signal processor):
Structure: It is composed of receiving demodulator, transmitting modulator, transmitting phase detector and other circuits; the new mobile phone also integrates high-power tube, frequency synthesis, 26M oscillation and frequency division circuit inside (as shown in the figure below).
effect:
a) The internal high-power tube amplifies the weak current sensed by the antenna;
b) When receiving, demodulate the receiving carrier signal (with the other party's information) of 935M-960M (GSM) and the local oscillator signal (without information) to obtain the receiving baseband information of 67.707KHZ;
c) When transmitting, the transmission information processed by the logic circuit and the local oscillator signal are modulated into the transmission intermediate frequency;
d) Combine 13M/26M crystal to generate 13M clock (reference clock circuit);
e) Generate a local oscillator signal that matches the mobile phone's operating channel based on the reference signal sent by the CPU.
3. Signal receiving process
When the mobile phone receives, the antenna converts the electromagnetic waves sent by the base station into weak AC current signals, which are sent to the high-frequency filter to filter out other useless noise through the antenna switch receiving path to obtain a pure 935M-960M (GSM) receiving signal. After being coupled by a capacitor, it is sent to the corresponding high-frequency tube inside the intermediate frequency for amplification, and then sent to the demodulator and the local oscillator signal (without information) for demodulation to obtain 67.707KHZ receiving baseband information (RXI-P, RXI-N, RXQ-P, RXQ-N); it is sent to the logic audio circuit for further processing.
Structure and working principle of transmitting circuit
During transmission, the transmission baseband information processed by the logic circuit is modulated into the transmission intermediate frequency, and the transmission intermediate frequency signal is converted to the frequency signal of 890M-915M (GSM) by TX-VCO. After amplification by the power amplifier, it is converted into electromagnetic waves and radiated by the antenna.
The key points of this circuit are: (1) circuit structure; (2) functions and effects of each component; (3) signal transmission process.
1. Circuit structure
The transmitting circuit is composed of the transmitting modulator and phase detector inside the intermediate frequency; transmitting voltage-controlled oscillator (TX-VCO), power amplifier (PA), power controller (PC), transmitting mutual inductor and other circuits. (As shown below)
▲Block diagram of transmitting circuit
2. Functions and effects of each component
1) Transmit modulator:
Structure: The transmit modulator is inside the intermediate frequency, which is equivalent to the MOD in the broadband network.
Function: During transmission, the transmission baseband information (TXI-P; TXI-N; TXQ-P; TXQ-N) processed by the logic circuit is modulated with the local oscillator signal into the transmission intermediate frequency.
2) Transmitter voltage-controlled oscillator (TX-VCO):
Structure: The transmitter voltage-controlled oscillator is a capacitor three-point oscillation circuit that controls the output frequency by voltage; it is integrated into a small circuit board during manufacturing, and leads to five pins: power supply pin, ground pin, output pin, control pin, and 900M/1800M frequency band switching pin. When there is a suitable working voltage, it oscillates to generate a corresponding frequency signal.
Function: Convert the transmitting intermediate frequency signal modulated by the intermediate frequency modulator into the 890M-915M (GSM) frequency signal that the base station can receive.
Principle: As we all know, the base station can only receive the frequency signal of 890M-915M (GSM), but the intermediate frequency signal modulated by the intermediate frequency modulator (such as Samsung's transmitting intermediate frequency signal 135M) cannot be received by the base station. Therefore, TX-VCO is used to convert the transmitting intermediate frequency signal into the frequency signal of 890M-915M (GSM).
When transmitting, the power supply sends out 3VTX voltage to make TX-VCO work, and generates 890M-915M (GSM) frequency signal in two ways: a) Sampling is sent back to the intermediate frequency, mixed with the local oscillator signal to generate a transmission frequency discrimination signal equal to the transmission intermediate frequency, and sent to the phase detector for comparison with the transmission intermediate frequency; if the TX-VCO oscillation frequency does not match the working channel of the mobile phone, the phase detector will generate a 1-4V jump voltage (DC voltage with AC transmission information) to control the capacitance of the variable capacitance diode inside the TX-VCO, so as to achieve the purpose of adjusting the frequency accuracy. b) It is sent to the power amplifier, amplified, and then converted into electromagnetic waves by the antenna for radiation.
From the above, we can see that: the frequency is generated by the TX-VCO, sampled and sent back to the intermediate frequency, and then a voltage is generated to control the operation of the TX-VCO; a closed loop is formed, and the frequency phase is controlled, so this circuit is also called a transmitting phase-locked loop circuit.
3) Power amplifier (power amplifier):
Structure: The current mobile phone power amplifier is a dual-band power amplifier (900M power amplifier and 1800M power amplifier integrated into one), divided into two types: vinyl power amplifier and iron shell power amplifier; different models of power amplifiers cannot be interchanged.
Function: Amplify the frequency signal oscillated by the TX-VCO, obtain sufficient power current, and convert it into electromagnetic waves for radiation through the antenna.
It is worth noting that the power amplifier amplifies the amplitude of the transmitting frequency signal, but cannot amplify its frequency.
Working conditions of power amplifier:
a) Working voltage (VCC): The power supply of the mobile phone amplifier is directly provided by the battery (3.6V);
b) Ground terminal (GND): to make the current form a loop;
c) Dual-frequency power switching signal (BANDSEL): controls the power amplifier to work at 900M or 1800M;
d) Power control signal (PAC): controls the amplification amount (working current) of the power amplifier;
e) Input signal (IN); output signal (OUT).
4) Transmitter transformer:
Structure: Two coils with equal wire diameter and number of turns are close to each other and are composed using the principle of mutual inductance.
Function: Sample the power amplifier transmitting power current and send it to the power control.
Principle: When the power amplifier transmits power current through the transmitting transformer, it induces a current of the same magnitude as the power current on its secondary side, which is then sent to the power control after detection (high-frequency rectification).
5) Power level signal:
The so-called power level means that engineers divide the receiving signal into eight levels when programming the mobile phone. Each receiving level corresponds to a level of transmission power (as shown in the following table). When the mobile phone is working, the CPU judges the distance between the mobile phone and the base station based on the received signal strength and sends out the appropriate transmission level signal to determine the amplification of the power amplifier (that is, when the reception is strong, the transmission is weak).
Attached is the power rating table:
6) Power controller (power control):
Structure: It is an operational comparator amplifier.
Function: Compare the transmit power current sampling signal with the power level signal to obtain a suitable voltage signal to control the amplification of the power amplifier.
Principle: When the power current passes through the transmitting transformer during transmission, the current induced on its secondary side is sent to the power control after detection (high-frequency rectification); at the same time, the preset power level signal is also sent to the power control during programming; after the two signals are compared internally, a voltage signal is generated to control the amplification of the power amplifier, so that the working current of the power amplifier is moderate, which saves electricity and prolongs the service life of the power amplifier (the higher the power control voltage, the greater the power of the power amplifier).
3. Signal transmission process
When transmitting, the transmission baseband information (TXI-P;TXI-N;TXQ-P;TXQ-N) processed by the logic circuit is sent to the transmission modulator inside the intermediate frequency and modulated with the local oscillator signal into the transmission intermediate frequency. The intermediate frequency signal base station cannot receive, and the TX-VCO must be used to increase the frequency of the transmission intermediate frequency signal to 890M-915M (GSM) so that the base station can receive it. When the TX-VCO is working, the frequency signal of 890M-915M (GSM) is generated and divided into two paths:
a) One channel of sampling is sent back to the IF, mixed with the local oscillator signal to generate a transmit detection signal equal to the transmit IF, and sent to the phase detector for comparison with the transmit IF; if the TX-VCO oscillation frequency does not match the working channel of the mobile phone, the phase detector will generate a 1-4V jump voltage to control the capacitance of the varactor diode inside the TX-VCO to achieve the purpose of adjusting the frequency.
b) Two-way input to the power amplifier is amplified and converted into electromagnetic waves by the antenna for radiation. In order to control the power amplifier amplification, when the power current passes through the transmitting transformer during transmission, the current induced on its secondary side is sent to the power control after detection (high-frequency rectification); at the same time, the preset power level signal is also sent to the power control during programming; after the two signals are compared internally, a voltage signal is generated to control the power amplifier amplification, so that the working current of the power amplifier is moderate, which saves electricity and prolongs the service life of the power amplifier.
3. Current status of domestic RF chip industry chain
In the field of RF chips, the market is mainly monopolized by overseas giants, including Qrovo, Skyworks and Broadcom. In terms of domestic RF chips, no company can independently support the IDM operation model, mainly Fabless design companies. Domestic companies have formed a "soft IDM" operation model through the coordination of design, foundry and packaging.
In terms of RF chip design , domestic companies have made some achievements in 5G chips and have certain shipping capabilities. RF chip design has a high threshold. After having RF development experience, it can accelerate the development of subsequent advanced RF chips. At present, companies with RF chip design capabilities include Unisoc, Vigor, Zhongpu Micro, Guomin Feixiang, Zhongke Hantianxia, Guangzhou Smart Microelectronics, ZTE, Rapoo Technology, Huahong Design, Jiangsu Juxin, and AESTEK.
In terms of RF chip foundry , Taiwan has become the world's largest compound semiconductor chip foundry. The main foundries in Taiwan are Win Semiconductors, Macronix and Universal. Only Sanan Optoelectronics and HiWafer have begun to get involved in compound semiconductor foundry in China. Sanan Optoelectronics is currently the most complete domestic layout in China, with GaAs HBT/pHEMT and GaNSBD/FET process layout. It is currently cooperating with more than 200 domestic enterprises and institutions, and more than 10 chips have passed performance verification and are about to be mass-produced. HiWafer is a subsidiary of Hitech High-Tech Holdings, a joint venture with China Electronics Technology Group Corporation 29, and currently has GaAs 0.25um PHEMT process capability.
In terms of RF chip packaging , the higher frequency of 5G RF chips has a greater impact on circuit performance due to the connection lines in the circuit, so the length of the signal connection lines needs to be reduced during packaging; on the other hand, the power amplifier, low-noise amplifier, switch and filter need to be packaged into a module, which can reduce the volume and facilitate the use of downstream terminal manufacturers. In order to reduce the parasitics of RF parameters, Flip-Chip, Fan-In and Fan-Out packaging technologies are required.
When using Flip-Chip, Fan-In, or Fan-Out packaging processes, there is no need to use gold bonding wires for signal connection, which reduces the parasitic electrical effects caused by the gold bonding wires and improves the chip's RF performance. In the 5G era, high-performance Flip-Chip/Fan-In/Fan-Out combined with Sip packaging technology will be the future packaging trend.
Flip-Chip/Fan-In/Fan-Out and Sip packaging are advanced packaging, and their profitability is much higher than that of traditional packaging. After the domestic listed company, Changdian Technology acquired STATS ChipPAC, it formed a complete FlipChip+Sip technology packaging capability.
IV. Conclusion: Opportunities outweigh challenges
The business model of China's consumer IC industry in the past and future decades can be summarized as follows:
1. Micro-innovation
2. Applications are launched at the mature stage
3. Basic performance is enough
4. Price is the killer
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China's IC industry is heavily dependent on imports, and the localization rate is extremely low, but this also means that there is huge room for localization;
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Consumer electronics ICs lag behind developed countries such as the United States and Japan in all aspects. Breakthroughs in performance are both difficult and critical.
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The RF filters for mobile terminals are basically monopolized by international giants, and the domestic market prospects are still huge;
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The investment in RF chips is relatively small, so it is a good trial point and breakthrough point. Improving performance is the key.
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Domestic RF chip companies are small and scattered. Only by joining forces, integrating, and giving up competition in the internal low-end market can they have a chance to challenge international giants.
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Today, the industry environment is favorable, and the government, capital and the whole society have given great support and attention. There is at least a 10-year window period, and domestic enterprises should seize the opportunity;
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There is no shortcut in the IC industry. It must continue to make mistakes and requires active participation from the government, capital and practitioners.
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