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RF Front End (RF Front End) is the only way for the antenna and RF transceiver chip. It is responsible for the transmission and reception of wireless electromagnetic wave signals, and is the core module for mobile terminal equipment to realize cellular network connection, Wi-Fi, Bluetooth, GPS and other wireless communication functions.

The RF front-end chip usually integrates a variety of different devices, and the types and quantities of the devices integrated in different terminals are also different. In most cases, the RF front-end chip includes a power amplifier (PA), a filter (Filter), a duplexer or a multiplexer (Duplexer or Multiplexer), a low noise amplifier (LNA), a switch (Switch), an antenna tuning module (ASM), and other devices. In the RF front-end architecture of some terminals, a double-pass device (Diplexer) and a connector (Coupler) are also added after the antenna switch.

Different devices do not do their own tasks, but coordinate with each other: the radio frequency power amplifier (PA) is used to amplify the radio frequency signal of the transmission channel; The radio frequency low noise amplifier (LNA) is used to amplify the radio frequency signal of the receiving path. Diplexer is used to isolate the transmitting signal and the receiving signal. The filter is used to reserve the signal of a specific frequency band and filter out the signal outside the specific frequency band. The radio frequency switch is used to realize the conversion, RF signals of different frequency bands are concentrated on the same path.

In addition, different devices also affect the communication quality of the whole machine: for example, the link insertion loss of the entire front end affects the power and sensitivity of the radio frequency signal, the PA amplification performance affects the power of the transmitted signal, the LNA amplification performance affects the sensitivity of the received signal, and the filter affects the out-of-band spurious index of the radio frequency signal.

From 2G to 5G, the RF front-end design has been very different:

On the one hand, the number of chips in mobile terminal equipment has increased sharply, and the overall value has been rising. For example, the value of RF front-end in high-end 4G mobile phones has reached 17 times that of 2G mobile phones, while the value of RF front-end in 5G era has reached more than twice that of 4G;

On the other hand, the space left by mobile terminal equipment for RF front-end chips has not increased. In the past, the circuit design of RF front-end module focused on the design of power amplifier (PA), pursuing low-voltage operation, high-power output and high-power, so as to conform to the use of low-voltage batteries, thereby reducing the volume and achieving the purpose of saving electricity [10]. However, with more and more functions, manufacturers can only improve the integration of RF front-end, to meet the existing design needs, which will inevitably increase the entry threshold of the middle and high-end market.