Perception Technology of Industrial Internet of Things - UHF RFID

Today, smart manufacturing systems use data Stored in RFID tags to enable more flexible and efficient customized products. The application of RFID technology on the factory floor has brought about a higher level of automation and standardization, and has made extensive contributions to the "lean" process of the modern supply chain. Compared with existing identification technologies, such as active tags and barcodes, passive RFID tags do not need their own power supply and do not require line of sight to operate, which has great advantages.

According to a 2020 report by Prudour researchers, the combined consumer and industrial IoT markets are expected to reach $11.1 trillion by 2025; the global battery-free RFID sensor market is expected to grow at a compound annual growth rate of 13.3%; It will reach $209.9 million by 2030. The dramatic expansion of IoT applications has raised some issues related to the batteries that power IoT devices—not only in terms of sustainability and environmental protection, but also from a predictability and cost perspective. Therefore, developers of Industry 4.0 are looking for battery-free solutions. Then, passive RFID devices and passive RFID tags undoubtedly meet this demand.

Passive RFID technology does not require special software and hardware, and the data transmission from the RFID tag to the RFID Reader only takes a few milliseconds, and it is fully compliant with the current EPC Gen2 protocol. The benefit to the user is that no special hardware or software is required to acquire and process measurements. RFID readers currently available in the market can capture and parse data from RFID tags and send it to higher level systems. For example, Asset IDs and EPC numbers can be captured along with sensor data when integrating read-write chip-based RFID tags into logistics applications. Inlays can be converted to a variety of transponder formats, from flexible tags to hard tags. Classic packaged versions, such as QFN integrated sensor ICs, are suitable even in harsh environments.

RFID technology is located in the perception layer of the Internet of Things, which is the basis for the development of the Internet of Things and the prerequisite for the realization of the Internet of Things. Compared with RFID tags of other frequencies, UHF tags are more secure and penetrable. With UHF readers, they can better resist interference and have faster read and write speeds. Therefore, in recent years, its development is more rapid and its application is very extensive. So, what are the signal propagation methods of UHF RFID, mainly including linear polarization and circular polarization:

Linear polarization: An electromagnetic wave in which the orientation of the electric field vector is fixed in space is called linear polarization. Sometimes the ground is used as a parameter, the direction of the electric field vector parallel to the ground is called horizontal polarization, and the direction perpendicular to the ground is called vertical polarization.

Circular polarization: When the angle between the polarization plane of radio waves and the normal plane of the earth changes from 0 to 360°, that is, the magnitude of the electric field remains constant and the direction changes with time, the trajectory of the end of the electric field vector is perpendicular to the propagation When the projection on the plane of the direction is a circle, it is called circular polarization.

Circularly polarized antennas can receive radio waves of any polarization, and their radiated waves can also be received by any polarized antenna; circularly polarized antennas have rotation orthogonality; polarized waves are incident on symmetrical targets (such as planes, spheres, etc.) When the rotation direction is reversed, electromagnetic waves with different rotation directions have a larger value of polarization isolation.