In the era of mobile Internet, mobile phones integrate more and more RF technologies, such as dual-mode/multi-mode mobile phones supporting multiple standards in LTE, TD-SCDMA, WCMDA, CDMA2000, HSDPA, EDGE, GPRS, and GSM. , navigation, automatic payment, TV reception Wi-Fi, GPS, RFID, NFC mobile phones. The use of a variety of RF technologies has made the design of mobile phones more complex.
Mobile phone RF technology and mobile phone RF module basic compositionThe RF part of 3G mobile phone consists of two parts: RF receiving and RF transmitting. The main circuits include antenna, wireless switch, receiving filter, frequency synthesizer, high frequency amplification, receiving local oscillator, mixing frequency, intermediate frequency, transmitting local oscillator, power amplifier control, Amplifier and so on.
In general, the key components in the basic mobile phone RF part mainly include RF transceiver (Transceiver), power amplifier (PA), antenna switch module (ASM), front-end module (FEM), duplexer, RF SAW filter and Synthesizer, etc., as shown. The following will focus on three basic parts:
Figure mobile phone RF module basic composition diagram
Mobile phone RF module power amplifier (PA)A power amplifier (PA) is used to amplify the RF signal output by the transceiver. The field of power amplifiers is an independent field with thresholds, and it is also a component that cannot be integrated in mobile phones. At the same time, this is also the most important component in mobile phones. The performance of mobile phones, the area of ​​calls, the quality of calls, the strength of mobile phones, and the battery life are all powered by power. The amplifier decides.
The main manufacturers in the power amplifier field are RFMD, Skyworks, TriQuint, Renesas, NXP, Avago, ANADIGICS. Now, Qualcomm, which was originally a PA corporate partner, has also directly joined the PA market. It will launch a PA produced in CMOS process in the second half of 2013, supporting LTE-FDD, LTE-TDD, WCDMA, EV-DO, CDMA 1x. Seven modes, TD-SCDMA and GSM/EDGE, the spectrum will cover more than 40 frequency bands in use worldwide, and announced its entry into the PA industry with multi-frequency and multi-mode advantages.
After the PA market experienced the LDMS PA “擂主†era, gallium arsenide (GaAs) PA became the “master†of the PA market in the 3G era. TriQuint, which led the GaAs attack on the PA market, is actively deploying a blueprint for GaAs, and launches a high-efficiency multi-frequency multimode power amplifier MMPA for 3G/4G smartphone expansion connections.
Qualcomm is attacking the PA market with CMOS PA. In the future, PA may become a part of the mobile phone platform, and there will be a phenomenon in which mobile phone chip platform companies acquire and merge PA companies.
How to integrate these different frequency bands and standards of power amplifiers is an important topic that the industry has been studying. There are currently two options: one is a converged architecture that integrates PAs of different frequency RF power amplifiers; the other is the integration along the signal link, which integrates the PA with the duplexer. Both options have advantages and disadvantages and are applicable to different mobile phones. The fusion architecture, PA's high integration, has a significant size advantage for more than three frequency bands, and there are significant cost advantages in 5-7 bands. The disadvantage is that although the PA is integrated, the duplexer is still quite complex, and the PA is integrated with switching losses, and performance is affected. For the latter architecture, the performance is better, and the integration of the power amplifier and the duplexer can improve the current characteristics, which can save about tens of milliamps of current, which is equivalent to extending the talk time by 15%. Therefore, the industry's suggestion is that when there are more than 6 frequency bands (not counting 2G, 3G and 4G), the fusion architecture is adopted, and when it is less than four frequency bands, the PAD integrated with the duplexer is adopted. At present, TriQuint can provide two architectures. RFMD mainly prefers the architecture of converged PA, and Skyworks prefers multi-frequency PAD scheme.
Mobile phone RF module RF transceiverThe transceiver is the core processing unit of the mobile phone radio frequency, and mainly comprises a receiving unit and a transmitting unit. The former completes the amplification, filtering and down-conversion of the received signal and finally outputs the baseband signal. The RF to baseband conversion is usually implemented by using zero intermediate frequency and digital low intermediate frequency; the latter performs upconversion, filtering, and amplification of the baseband signal. The conversion of the baseband signal to the radio frequency signal is mainly implemented by means of secondary frequency conversion. When the RF/IF (IC/IF) IC receives the signal, the receiving unit receives the signal from the antenna (about 800 Hz to 3 GHz), and then amplifies, filters, and synthesizes the signal, and then down-converts the RF signal to baseband, followed by baseband signal processing. When the RF/IFIC transmits a signal, the baseband below 20 kHz is subjected to up-conversion processing, and converted into a signal in the radio frequency band and then transmitted.
In the past few years, transceiver manufacturers have been divided into two categories. One is based on the fundamental frequency platform, and the transceiver is used as part of the platform, such as Qualcomm, NXP, Freescale and MediaTek. This is because the transceiver is very closely related to the fundamental frequency, and both often require a collaborative design. The other is a professional RF manufacturer that does not rely on the baseband platform to expand the transceiver market, such as Infineon, STMicroelectronics, and Skyworks.
As transceivers evolve toward integration and multi-mode, single-mode transceivers are fully integrated into the baseband. RF front-end devices in different frequency bands and formats have also been produced in different ways. Discrete RF transceivers are becoming less common.
Mobile RF Front End Module (FEM)The front-end module integrates switches and RF filters to perform antenna reception and transmission switching, frequency band selection, reception and transmission of RF signal filtering. In the frequency band below 2 GHz, many RF front-end modules are gradually becoming mainstream with silicon integrated circuit processes such as complementary metal oxide semiconductor (CMOS), bipolar junction transistor (BJT), silicon germanium (SiGe) or Bipolar CMOS. Because silicon integrated circuits have mature processes, which are large enough to design large and complex circuits, and can be designed together with intermediate frequency and fundamental frequency circuits, they have great potential for development. Other heterostructure transistors are also emerging in special-purpose circuits; however, in the frequency band above 5 GHz, their performance in low noise characteristics, high power output, and power increase efficiency is much inferior to that of GaAs field effect transistors. The gallium field effect transistor process still has an advantage in the performance of electrical functions. In the past, RF front-end module circuit design focused on the design of power amplifiers, pursuing low-voltage operation, high-power output, high power and increased efficiency to meet the requirements of using low-voltage batteries to reduce the size and achieve power saving. Power increase efficiency and linearity often cannot be balanced. However, under the extensive use of digital modulation technology, how to maintain good linearity has become an inevitable research focus.
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