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What are the principles and technical parameters of RFID tag?

Principle of RFID tag

The basic working principle of RFID technology is not complicated: after the tag enters the magnetic field, it receives the RF signal from the reader, and sends the product information (passive tag, passive tag or passive tag) stored in the chip with the energy obtained by the induced current, or sends the signal of a certain frequency (active tag, active tag or active tag); the reader reads the information and After decoding, it is sent to the central information system for data processing.

RFID (radio frequency identification) system consists of two parts: read / write unit and electronic transceiver. The reader sends out electromagnetic pulses through the antenna, and the transceiver receives these pulses and sends the stored information to the reader as a response. In fact, this is to read, write or delete the data in the memory.

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Technically, “smart tag” includes an RFID circuit consisting of an RFID chip with an RFID RF part and an ultra-thin antenna loop, which is embedded in the tag together with a plastic sheet. Usually, there is a paper label attached to the label, which can clearly print some important information. Currently, smart tags are generally the size of credit cards. For small goods, there are 4.5 × 4.5cm labels, and there are also circular labels with a diameter of 4.7cm used on CDs and DVDs.

Compared with other ID technologies such as barcode or magnetic stripe, the advantage of transceiver technology lies in the wireless link between reader and transceiver: the read / write unit does not need visual contact with the transceiver, so it can be fully integrated into the product. This means that the transceiver is suitable for harsh environments and is insensitive to moisture, dirt and mechanical effects. Therefore, the transceiver system has very high reading reliability, fast data acquisition, and the last and important point is to save labor and paper.

Technical parameters of RFID tag

The technical parameters of electronic tag mainly include the energy requirement of tag activation, the reading and writing speed of tag information, the transmission rate of tag information, the capacity of tag information, the package size of tag, the read-write distance of tag, the reliability of tag, the working frequency of tag and the price of tag.

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1. Energy requirements for tag activation

When the electronic tag enters the working area of the reader, it is excited by the RF signal from the reader and the tag enters the working state. The activation energy of tag refers to the energy range required to activate the electronic tag chip circuit, which requires that the tag and the reader should be within a certain distance, and the reader can provide enough RF field strength for the tag.

2. Reading and writing speed of label information

The read-write speed of the tag includes the read-out speed and the write speed. The read-write speed refers to the reading speed of the electronic tag by the reader writer, and the writing speed refers to the writing speed of the electronic tag information. Generally, the reading and writing speed of the tag information is millisecond.

3. Package size of label

The package size of the tag mainly depends on the size of the antenna and the power supply. There are different requirements for the package size in different occasions. The small package size is millimeter level, and the large package size is decimeter level.

If the size of the electronic tag is small, it can be used in a wide range of applications, whether large or small items can be set. However, it is not a good thing to blindly pursue small size. If the design of electronic tag is relatively large, the size of antenna can be increased, so the reading rate of electronic tag can be effectively improved.

4. The capacity of label information

The amount of information that can be written into the tag refers to the amount of data that can be carried by the tag. The capacity of tag information is related to whether the electronic tag is “foreground” or “background”.

5. Label alignment distance

The read-write distance of tag refers to the working distance between tag and reader. The reading and writing distance of the label is millimeter level, and the far distance is more than 20 meters. In addition, most systems have different read distance and write distance. The write distance is about 40% ~ 80% of the read distance.

6. Transmission rate of label information

The transmission rate of tag information includes two aspects: one is the transmission rate of feedback data from the electronic tag to the reader writer, and the other is the rate of writing data from the reader.

7. Working frequency of tags

The working frequency of the tag refers to the frequency used when the tag works, which can be low frequency, high frequency, ultra-high frequency and microwave.

8. Reliability of labels

The reliability of the tag is related to the working environment, size, material, quality and the distance between the tag and the reader. For example, on a conveyor belt, when the label is exposed and is a single read, the accuracy of reading is close to 100%. However, many factors may reduce the reliability of tag reading and writing. The more tags are read at one time, the faster the tag moves, the more likely there will be misreading or missing reading.

The investigation in a project application shows that when 10000 electronic tags are used, 60 electronic tags are damaged in a year, and the proportion of damage is less than 0.1%. In order to prevent the inconvenience caused by the damage of electronic labels, the simultaneous use of barcode and electronic tags is an effective remedy, which can quickly copy an electronic tag according to the information recorded in the barcode. In addition, putting two electronic tags on an item in case of emergency is also a method, but it will make the whole project more expensive.

Post time: Aug-05-2020
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