RFID (Radio Frequency Identification Technology) is a non-contact automatic identification technology that has matured since the 1980s. It automatically recognizes target objects and acquires relevant data through RF signals. Conceptually, RFID is similar to bar code scanning. For bar code technology, it attaches the coded bar code to the target and uses a dedicated scanning reader to transmit information from strip magnet to scan read and write using photoelectric signals. RFID uses a dedicated RFID reader and a dedicated RFID unit that can be attached to the target to transmit information from the RFID unit to the RFID reader using RF signals. The RFID unit carries various types of related information about the target object, such as the name of the target object, the start and end point of the target transportation, the transit point, and the specific time when the target object passes through a certain place, etc., and can also load such as temperature. And other indicators. RFID units, such as labels, cards, etc., can be flexibly attached to various items from the vehicle to the cargo chassis.
(1) The most basic RFID system components:
Reader: A device that reads (and sometimes writes) tag information and can be designed to be handheld or fixed;
Antenna: Transmits RF signals between the tag and the reader.
The electronic tag generally stores electronic data in an agreed format. In practical applications, the electronic tag is attached to the surface of the object to be identified. The reader can read and recognize the electronic data stored in the electronic tag without contact, thereby achieving the purpose of automatically identifying the object. Usually the reader is connected to the computer, and the read tag information is transmitted to the computer for further processing. (In addition to the above basic configuration, the corresponding application software should also be included.
Tag: consists of a coupling element and a chip. Each tag has a unique electronic code attached to the object to identify the target object. Each tag has a globally unique ID number, UID. The UID is when the chip is made. It can't be modified in the ROM. The user data area (DATA) is for the user to store data, and can be read, written, overwritten, and added. There are three types of operations on the tag by the reader:
Identify: read the UID;
Read: Read user data;
Write: Write user data
(2) The working principle of the RFID system:
In practical applications, the RFID tag is attached to the surface of the object to be identified, and the electronic tag stores the electronic data in an agreed format. The reader can read and recognize the electronic data stored in the electronic tag without contact, thereby achieving the purpose of automatically recognizing the object. The reader sends a certain frequency of the RF signal through the antenna. When the tag enters the magnetic field, it generates an induced current to obtain energy, and sends out its own code and other information, which is read and decoded by the reader and sent to the host computer for processing.
(3) Working frequency of RFID system:
Usually the frequency used by the reader to transmit is called the operating frequency of the RFID system. Common operating frequencies are low frequency 125kHz, 134.2kHz and 13.56MHz and so on. Low-frequency systems generally refer to operating frequencies less than 30 MHz. Typical operating frequencies are: 125 kHz, 225 kHz, 13.56 M, etc. Radio frequency identification systems for these frequency applications are generally supported by corresponding international standards. The basic characteristics are that the cost of the electronic label is low, the amount of data stored in the label is small, the reading distance is short, and the electronic label has various shapes (card shape, ring shape, button shape, pen shape), and the reading antenna is not strong in orientation. Wait.
High-frequency systems generally refer to operating frequencies greater than 400 MHz. Typical operating frequencies are: 915 MHz, 2.45 GHz, 5.8 GHz, and so on. High frequency systems are also supported by numerous international standards in these bands. The basic characteristics of the high-frequency system are the high cost of the electronic tag and the reader, the large amount of data stored in the tag, and the long reading distance (up to several meters to ten meters), which is suitable for high-speed motion performance of objects, and generally has a card shape. Shape, reading antenna and electronic tag antenna have strong directionality.
(4) RFID tag type
RFID tags are classified into passive tags and active tags. The active tag itself is battery-powered and has a large read/write distance. It is more expensive than passive tags. It is also called an active tag. It generally has a far reading distance. The disadvantage is that the battery cannot last long. Use, need to replace the battery after the energy is exhausted.
After receiving the microwave signal from the reader (reading device), the passive electronic tag converts part of the microwave energy into direct current for work. Generally, it is maintenance-free, low in cost and has a long service life. Active tags are smaller and lighter, and read and write distances are closer, also known as passive tags. Compared to active systems, passive systems have slightly limited reading distances and speed of adaptation to objects.
According to whether the stored information is rewritten, the label is also divided into a read-only label and a read-write label. The information in the read-only label is written at the time of production of the integrated circuit, and cannot be written later. Modifications can only be read by special equipment; readable and writable tags write the saved information to its internal storage area, and can also be erased by special programming or writing devices when rewriting is required. Generally, the time it takes to write information into an electronic tag is much longer than the time it takes to read the electronic tag information. The time taken for writing is in the order of seconds, and the time taken for reading is in the order of milliseconds.
RFID technology features and advantages
RFID is a flexible application technology that is easy to handle, simple and practical, and especially suitable for automated control. The identification work can be supported by a read-only mode or a read-write mode without manual intervention. Can work freely in a variety of harsh environments: short-range RF products are not afraid of oily, dusty and other harsh environments, can replace bar codes, such as used in the factory line to track objects; long-range RF products are used for transportation, identification distance can be Up to tens of meters, such as automatic charging or identification of vehicle identity. Its unique superiority is beyond the reach of other identification technologies.
Mainly have the following characteristics:
Easy to read: Data is read without a light source, or even through an outer package. The effective recognition distance is larger, and when the active label with the battery is used, the effective recognition distance can reach more than 30 meters;
Fast recognition speed: When the tag enters the magnetic field, the reader can read the information in real time, and can process multiple tags at the same time to realize batch identification;
Large data capacity: The two-dimensional barcode (PDF417) with the largest data capacity can only store up to 2725 numbers; if it contains letters, the storage will be less; the RFID tags can be expanded to tens of K according to the needs of users;
Long service life and wide application range: its radio communication method can be applied to dusty, oily and other highly polluting environments and radioactive environments, and its closed packaging makes its lifespan greatly exceed the printed bar code;
Tag data can be dynamically changed: the programmer can write data to the end, giving the RFID tag the ability to interactively load portable data files with less write time than printed bar codes;
Better security: not only can be embedded or attached to different shapes and types of products, but also can be password protected for reading and writing of tag data, thus providing higher security;
Dynamic real-time communication: the tag communicates with the reader at a frequency of 50 to 100 times per second, so that as long as the object attached to the RFID tag appears within the effective recognition range of the reader, its position can be dynamically tracked and monitored. .