According to the estimation of market analysts, in the field of radio frequency identification technology, there are mainly low frequency and ultra high frequency, of which high frequency and ultra high frequency are widely used. The high-frequency reader / writer can generally meet many international standards such as iso18000-3, iso15693 / iso14443a / B, and can be widely used in many fields such as open access control, open attendance, meeting sign in, barrier free access, valuables management, digital entrance ticket management, library management, medical management, product anti-counterfeiting, logistics and supply chain. The RF printer has the function of printing plaintext information on the surface of the electronic label in real time and reading / writing the label. It can facilitate machine reading and manual reading at the same time. It can be widely used in the fields of logistics, transportation, production line automation, medical care, book management and animal husbandry management.
The RFID system includes at least two parts, an electronic tag and a reader. The RFID reader / writer performs wireless communication through the antenna, and can read or write the tag identification code and memory data. A typical reader includes a high frequency module (transmitter and receiver, control unit and reader antenna). RFID reading and writing are generally divided into the following low-frequency readers, high-frequency readers, dual frequency readers and 433MHz active readers. Working principle of RFID: in, the electronic tag is also called transponder and data carrier; Readers are also called reading devices, scanners, communicators and readers (depending on whether the electronic tag can wirelessly rewrite data).
There are two types of RF signal coupling between the electronic tag and the reader through the coupling element:
1. Inductive coupling:
The transformer model is coupled by the space high-frequency alternating magnetic field, which is based on the law of electromagnetic induction.
2. Electromagnetic backscatter coupling:
The radar principle model is based on the spatial propagation law of electromagnetic wave. The electromagnetic wave emitted is reflected when it meets the target and carries the target information.
Inductive coupling mode is generally suitable for short-range identification systems working at medium and low frequencies. Typical operating frequencies are 125 kHz / 225 kHz and 13.56 MHz. The recognition action distance is less than 1m, and the typical action distance is 10 ~ 20cra. The electromagnetic backscatter coupling mode is generally suitable for long-distance radio frequency identification systems working at high frequency and microwave. The typical operating frequencies are 433 MHz, 915 MHz, 2.45 GHz and 5.8 GHz. The recognition effect is greater than 1m, and the typical action distance is 3-10m
Influence of metal and liquid environment on RFID
RFID UHF tags are sensitive to metal and liquid environments due to the characteristics of electromagnetic backscattering, which may make it difficult for passive tags with this working frequency to work under objects with metal surfaces or liquid environments. However, such problems have been completely solved with the development of technology.
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