What does Radio Frequency(RF) means? Broadly defined, it should refer to high-frequency alternating electromagnetic waves in the range of 300KHZ to 300GHZ. Radio frequency technology is widely used in the field of wireless communication, and its definition range gradually evolves and develops with the times and technological applications. RFIC – radio frequency chip, we also call it MMIC. It refers to a component (module) 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 includes two parts: the receiving channel and the transmitting channel. The transmitting circuit is composed of transmitting modulator, transmitting phase detector, transmitting voltage-controlled oscillator (TX-VCO), power amplifier (power amplifier), power controller (power control), transmitting transformer and other circuits. When transmitting, the transmitting baseband information processed by the logic circuit is sent to the transmitting modulator, and after modulating with the local oscillator signal, the signal frequency is increased by TX-VCO to a frequency signal that the base station can receive.
When the TX-VCO works, the frequency signal is generated in two ways:
A. The sampling is sent back to the transmitting modulator, mixed with the local oscillator signal to generate a transmitting frequency discrimination signal, which is sent to the phase detector for comparison with the transmitting intermediate frequency; if it does not match the working channel, the phase detector will generate a jump Change the voltage to control the capacitance of the varactor diode inside the TX-VCO to achieve the purpose of adjusting the frequency.
B. The way into the power amplifier is converted into electromagnetic waves and radiated by the antenna after being amplified.
The receiving circuit consists of an antenna, an antenna switch, a filter, a high amplifier tube (low noise amplifier), a receiving demodulator and other circuits. When receiving, the antenna converts the electromagnetic wave sent by the base station into a weak AC current signal after filtering, and then passes through the antenna switch receiving channel, and sends a high-frequency filter to filter out other useless clutter. After high-frequency amplification, it is sent to the receiving demodulator and the local oscillator. The signal is demodulated, and the received baseband information is sent to the logic audio circuit for further processing. All the above devices and signal processing constitute a complete RF chip (or RF module).
RF chip application
RF chips are actually widely used. Many introductions take mobile phones as an example, so for radio frequency, consumers may think that, in addition to Bluetooth (2.4G), it is 3G, 4G, 5G and so on. In fact, when it comes to wireless communication, RF is everywhere. The following are some common applications of RFIC in daily life. Consumer electronics such as mobile phones are generally RFIC applications for 4G/5G communication; notebooks, wireless mice, etc. are generally 2.4G applications; wifi is generally 2.4G/5G RF applications. Involving automotive electronics may be 77G reversing radar, 24G distance monitoring and other radar modules; involving smart homes are mostly 2.4G RFIC applications, which are cheap, convenient and common; involving industrial wireless environment and environmental testing, it may be sub1GHZ, but also 2.4GHZ; Involving wireless meter reading, electricity meters are generally unified with consumer electronics and one step later than the development of consumer electronics. Now it has entered the development and application of 5G, and wireless meter reading has gradually changed from the 3G era to 4G module communication; while household gas meters and water meters Then generally use sub1GHZ. Smart buildings should be the most widely used and varied occasions for RFIC applications. For example, surveillance cameras use 4G communication to ensure real-time and fluency; smoke alarms use sub 1GHZ or 2.4GHZ to ensure timely communication with the gateway, and network communication is enough; The same is true for smart homes. However, for convenience and uniform standards, 2.4GHZ RFICs are generally used; in the past, 1GHZ RFICs were more commonly used in toys, and now many 2.4GHZ RFICs have gradually appeared, which is easy to connect with mobile phones.
With the upgrading of mobile phones, 3G, 4G, and 5G are familiar to everyone. It is nothing more than the use of different standards in different countries and different frequency bands of different operators. In addition to mobile phones, 2.4G is the most used in our lives, and 1G is the one that appears quietly and unknown (some manufacturers refer to the frequency bands within 1GHZ of 315/433/470/868/915MHZ). Today, I will mainly talk about the RFIC of these two frequency bands.
The difference between Sub-1GHZ and 2.4GHZ
Sub-1GHZ and 2.4GHZ are generally used in IoT scenarios and smart homes, toys, and environmental monitoring. In wireless communication applications in license-free frequency bands, the two wireless frequency bands, Sub-1GHZ and 2.4GHZ, are the main choices. The Sub-1GHZ wireless frequency band is suitable for setting up a wireless communication network with low data rate and low power consumption, and 2.4GHZ is more suitable for high data rate communication in a small area. Therefore, in the application, factors such as distance, power consumption, interference, and networking convenience are generally considered. This requires a comparison of the characteristics of Sub-1GHZ and 2.4GHZ RFICs.
First, Sub-1GHZ has relatively large coverage and is a better choice for large-scale connection networking (MESH networking as shown in Figure 3, communication between nodes can communicate with each other during busy hours, and upload gateways during idle hours) .
Second, Sub-1GHZ only needs a narrow bandwidth for wireless data transmission in applications with a small amount of data rather than high traffic such as video, and has low power consumption requirements for RF transceivers, which is suitable for battery power supply or energy harvesting power supply IoT device applications.
Third, lower bandwidth results in lower thermal noise and better receiver sensitivity. The use of Sub-1GHZ band systems can reduce the infrastructure cost of wireless network deployments.
In addition, relatively speaking, the close deployment of 2.4GHZ equipment will cause some interference to radio frequency, and the interference situation of Sub-1GHZ will be better than that of 2.4GHZ. Therefore, although we can often hear and come into contact with 2.4GHZ, Sub-1GHZ also has a wide range of applications.
The Sub-1GHZ frequency band is allocated and used for different radio transmission equipment, showing the characteristics of industrial application. Different radio transmission equipment has different frequency bands, which basically form two parts: dedicated frequency band and public frequency band. The dedicated frequency band is mainly for national defense, railway, public security, government, electric power and other system applications. Public frequency bands can be divided into licensed frequency bands and license-exempt frequency bands. Licensed frequency bands such as NB-IoT, LoRa, etc., license-exempt frequency bands are mainly public walkie-talkies, micro-power short-distance radio equipment, etc.
Sub-1GHZ RFIC applications are mainly based on remote control, voice and data communication. Remote control is applications such as access control, remote control and switches; voice is mainly walkie-talkies; data communication is generally Lora or NB-IOT wireless networking, large-scale application deployment is the main feature of data communication applications, the main typical application is wireless Meter reading. The Industrial Internet of Things has broader needs for Sub-1GHZ RFICs. At present, batteries for low-power IoT sensors or devices are the mainstream match. With the requirements for long battery life and the application of other energy harvesting (such as solar energy, wireless energy transmission, etc.) power supply methods, the application requirements for Sub-1GHZ RFIC transmit power consumption are getting higher and higher. There are many models of Sub-1GHZ RFICs from Acetech to meet the current low power consumption requirements.