The spectrum of wireless communication is limited, the distribution is very strict, and the electromagnetic waves of the same bandwidth can only be used once. In order to solve the problem of cumbersome and cumbersome, engineers have developed a lot of "modulation technology" and "multiplex technology" to increase the spectrum efficiency, so 3G, 4G, 5G technology of different communication era technology, then in our mobile phone, what components are responsible for handling these technologies for us?
First, modulation technology and multiplex technology
First of all, we must understand that "modulation technology" and "multi-technology" are completely different things. Let us first look at what is the difference between them?
Digital signal modulation technology (ASK, FSK, PSK, QAM):
The analog electromagnetic waves are modulated into different waveforms to represent two different digital signals, 0 and 1. ASK uses amplitude to represent 0 and 1, FSK uses frequency to represent 0 and 1, PSK uses phase (waveform) to represent 0 and 1, QAM uses both amplitude magnitude and phase (waveform) to represent 0 and 1.
Well, the digital signals 0 and 1 that each person's mobile phone antenna is going to transmit become electromagnetic waves of different waveforms. The problem is coming again. So many different waveforms of electromagnetic waves are thrown into the air, how to distinguish those that are yours (and What are you talking about, those are my (and I am talking)?
Multiplex technology (TDMA, FDMA, CDMA, OFDM):
Differentiate electromagnetic waves for different users. TDMA uses time to distinguish between yours and me. FDMA uses different frequencies to distinguish between yours and mine. CDMA uses different passwords (orthogonal spreading codes) to distinguish between yours and me. OFDM uses different positives. The subcarrier frequency is used to distinguish between yours and mine.
It is worth noting that digital signal modulation technology or multiplex technology is performed together when digital signals (0 and 1) are processed and processed. Generally, multiplex technology is first used to perform digital signal modulation technology. (except for OFDM), so multiplex technology and modulation technology must be used at the same time.
Digital modulation technology
The current mobile phone belongs to "digital communication", that is, the voice of our speech (continuous analog signal), which is first converted into discontinuous 0 and 1 digital signals by the mobile phone, and then converted into electromagnetic waves by digital modulation (analog signal) Carrying the digital signal), and finally transmitting it from the antenna, the principle is as shown.
Second, digital communication system architecture
The architecture of the digital communication system is shown in the figure. The user may use a smartphone to make a voice call or access the Internet for data communication. We explain the following:
Voice upload (speaking phone): After the sound is received by the microphone, it is a low-frequency analog signal, which is converted into a digital signal by a low-frequency analog-to-digital converter. The data is compressed by the “baseband chipâ€, and the cyclic repeat check code, channel code, and interlace are placed. , encryption, formatting, and then multiplex, modulation and other digital signal processing.
Next, it is converted into a high-frequency analog signal (electromagnetic wave) via an "IF chip" (IF), that is, a high-frequency digital analog converter (DAC); finally, electromagnetic waves of different time, frequency, and waveform are formed via a "radio frequency chip (RF)". It is transmitted by the antenna.
Voice download (listening to the phone): The antenna receives the electromagnetic waves of different time, frequency and waveform, and obtains the high frequency analog signal (electromagnetic wave) after being processed by the "radio frequency chip (RF)", and then passes the "IF chip" (IF). A high frequency analog to digital converter (ADC) converts to a digital signal.
Next, De-modulaTIon, De-mulTIplexing, De-formatTIng, De-ciphering, and de-interlacing are performed via "Bridge Chip (BB)". -inter-leaving), channel decoding, CRC, data decoding, etc., and finally converted to low frequency analog signals via low frequency digital analog converter (DAC) (Sound) is played back by the microphone.
Data communication (online): Basically, data communication is digital signal regardless of uploading or downloading, so it can be directly processed into the baseband chip (BB). Other processes are similar to voice communication, and will not be repeated here.
Note: The principle of communication is a lot of mathematics. Since the mobile phone is something we use every day, most people are curious about the feeling of communication and want to know more, but often go into the first class of the classroom to see It is a lot of complicated digital: Fourier Transform, Laplace Transform, Discrete, and immediately retreat. In order to simplify the complexity, it is easy for everyone to understand. The above is for digital communication systems. The introduction is just a gesture, and there will be a gap with the actual situation. It is recommended that those who are interested in further understanding can base on the above concepts to further understand the technical details.
Third, the wireless communication system architecture
Based on the previous introduction, let's take a look at several important integrated circuits (ICs) in smartphones, including: basic frequency (BB), intermediate frequency (IF), and radio frequency (RF). Each part may have one to several integrated circuits (ICs), or it may be a package of several integrated circuits (ICs), called "System in a Package (SiP)", or The chips are integrated into one, called "System on a Chip (SoC)".
Baseband chip: belongs to digital integrated circuit for digital signal compression/decompression, channel encoding/decoding, interleaving/de-interlacing, encryption/decryption, formatting/deformatting, multiplex/demultiplexing, Modulation/demodulation, as well as management of communication protocols, control of input and output interfaces, etc., famous mobile phone baseband chip suppliers include: Qualcomm, Broadcom, Marvell, MediaTek and so on.
Introduction: The spectrum of wireless communication is limited, the distribution is very strict, and the electromagnetic waves of the same bandwidth can only be used once. In order to solve the problem of many problems, engineers have developed many “modulation technologies†and “multiplexing techniques†to increase the spectrum efficiency. 3G, 4G, 5G technology of different communication era technology, then in our mobile phone, what components are responsible for handling these technologies for us?
Modulator: The digital signal processed by the baseband chip is converted into a high-frequency analog signal (electromagnetic wave), which can be transmitted very far. For those who want to know more about the communication principle, please refer to it here.
Mixer: Mainly responsible for the frequency conversion work, converting the modulated high frequency analog signal (electromagnetic wave) into the required frequency to match the frequency range (wireless spectrum) of different communication systems.
Synthesizer: Provides the operating frequency required for wireless communication electromagnetic waves and RF integrated circuits. It usually provides precise operation via "Phase Locked Loop (PLL) and "Voltage Controlled Oscillator"). frequency.
Bandpass filter: Only the high frequency analog signal (electromagnetic wave) of a specific frequency range (band) is passed, and the unnecessary frequency range is filtered out to obtain the frequency range (band) we need.
Power Amplifier: Before the high-frequency analog signal (electromagnetic wave) is transmitted, it must be amplified by a power amplifier (PA) to enhance the signal to be transmitted far enough. Transceiver: Transmitted (Tx:Transmitter) high frequency analog signal (electromagnetic wave) to the antenna, or received by the antenna (Rx: Receiver) high frequency analog signal (electromagnetic wave).
Low noise amplifier: used when receiving signals. The high frequency analog signal (electromagnetic wave) received by the antenna is very weak. It must be amplified by a low noise amplifier (LNA) before it can be processed.
Demodulator: used to receive signals, convert high-frequency analog signals (electromagnetic waves) into digital signals, and then transmit them to the baseband chip (BB) for digital signal processing.
Therefore, the principle of mobile phone uploading (talking phone) is: firstly, the digital audio signal is processed by the baseband chip (BB), and then converted into a high frequency analog signal by a modulator (Modulator), which is converted into a required by a mixer (Mixer). The frequency is obtained by a bandpass filter (BPF) to obtain a high frequency analog signal (electromagnetic wave) of a specific frequency range (band), which is enhanced by a power amplifier (PA) and finally transmitted by the transmission receiver (Tx) to the antenna output.
On the contrary, the principle of mobile phone downloading (listening to the phone) is: firstly, the high frequency analog signal (electromagnetic wave) is transmitted by the antenna, received by the transmitting receiver (Rx), and then obtained through a band pass filter (BPF) to obtain a specific frequency range ( The high frequency analog signal of the frequency band is amplified by a low noise amplifier (LNA), converted into a desired frequency by a mixer (Mixer), converted into a digital voice signal by a demodulator (Demodulator), and finally The digital voice signal is processed by the baseband chip (BB).
Fourth, communication related integrated circuits: fundamental frequency, intermediate frequency, radio frequency
The back end of the wireless communication system described above uses a baseband chip to process digital signals, and the integrated circuit (IC) used in the front end can be roughly divided into "RF chip" and "IF chip". Large categories, wafers made from different materials:
Also known as "Analog baseband", the concept is "high-frequency digital analog converter (DAC)" and "high-frequency analog-to-digital converter (ADC)", including: Modulator, solution Demodulators, usually also IF amplifiers and intermediate frequency band filters (IF BPF), usually composed of CMOS components made of silicon wafers, possibly several integrated circuits, which may be integrated into An integrated circuit (IC).
Also known as "RF integrated circuit", it is a general term for all chips that process high-frequency wireless signals, usually including: transceiver, low noise amplifier (LNA), power amplifier (PA), bandpass filter (BPF), synthesis Synthesizers, Mixers, etc., usually composed of MESFETs made of gallium arsenide wafers, HEMT components, or BiCMOS devices fabricated on germanium wafers, or CMOS devices fabricated from germanium wafers. A power amplifier made of gallium nitride (GaN) may be several integrated circuits, some of which may be integrated into one integrated circuit (IC).
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