Working principle and circuit analysis of RF chip

Dec 20,2024
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The most important cores in mobile terminals are RF chips and baseband chips. RF chips are 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 RF chips and baseband chips?

The relationship between RF chips and baseband chips

Let's talk about history first. Radio Frequency and Base Band both come from English literal translation. The earliest application of radio frequency is Radio - Radio Broadcast (FM/AM), which is still the most classic application of radio frequency technology and even in the field of radio.

The baseband is the signal with the center point of the band at 0Hz, so it is the most fundamental signal. Some people also refer to baseband as "unmodulated signal", and this concept was once correct. For example, AM is a modulated signal that does not require modulation and can be read through sound emitting components after reception. But for the modern communication field, baseband signals usually refer to signals that have been digitally modulated and have a spectral center point at 0Hz. And there is no clear concept indicating that the baseband must be analog or digital, it all depends on the specific implementation mechanism.

To get back to the point, baseband chips can be considered to include modems, but not just modems. They also include channel encoding and decoding, source encoding and decoding, and some signaling processing. RF chips can be seen as the simplest up and down conversion of baseband modulation signals. The so-called modulation refers to the process of modulating the signal that needs 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.

Working principle and circuit analysis

Radio frequency, abbreviated as RF, refers to radio frequency current, which is a high-frequency alternating current electromagnetic wave. It stands for Radio Frequency and represents the electromagnetic frequency that can radiate into space, with a frequency range between 300KHz and 300GHz.

AC current that changes less than 1000 times per second is called low-frequency current, while AC current that changes more than 10000 times per second is called high-frequency current, and RF is such a high-frequency current. High frequency (greater than 10K); Radio frequency (300K-300G) is a higher frequency band of high frequency; The microwave frequency band (300M-300G) is also a higher frequency band of radio frequency. Radio frequency technology is widely used in the field of wireless communication, and cable television systems adopt 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 a power amplifier, a low-noise amplifier, and an antenna switch. Related article: In depth analysis of antenna working principle. The RF chip architecture consists of two main parts: the receiving channel and the transmitting channel. The RF circuit block diagram is shown below.