The characteristics of RFID tags in various frequency bands in RFID technology and their application fields
For an RFID system, its frequency band concept refers to the frequency range of the tag signal that the reader sends, receives, and reads through the antenna. From the application concept, the operating frequency of the radio frequency tag is also the operating frequency of the radio frequency identification system, which directly determines various aspects of the system application. In an RFID system, the system works just like we usually listen to FM radio, and the RF tags and readers have to be modulated to the same frequency to work. The working frequency of the radio frequency tag not only determines the working principle of the radio frequency identification system (inductive coupling or electromagnetic coupling), the recognition distance, but also determines the difficulty level and equipment cost of the radio frequency tag and the reader. The frequency bands or frequencies occupied by RFID applications are recognized internationally, that is, in the ISM band. Typical operating frequencies are: 125 kHz, 133 kHz, 13.56 MHz, 27.12 MHz, 433 MHz, 902 MHz to 928 MHz, 2.45 GHz, 5.8 GHz, and the like.
Depending on the operating frequency, RFID tags can be classified into different types such as low frequency (LF), high frequency (HF), ultra high frequency (UHF), and microwave. The working principle of RFID in different frequency bands is different. RFID tags in LF and HF bands generally adopt the principle of electromagnetic coupling, while RFID in UHF and microwave bands generally adopt the principle of electromagnetic emission. At present, the frequencies widely used in the world are distributed in four kinds of bands, low frequency (125KHz), high frequency (13.54MHz), ultra high frequency (850MHz ~ 910MFz) and microwave (2.45GHz). Each frequency has its characteristics and is used in different fields, so to use it properly, you must first select the appropriate frequency.
1. Low frequency RFID tag
Low-frequency RFID tags, referred to as low-frequency tags, have low security and confidentiality. Its operating frequency range is 30kHz ~ 300kHz. Typical operating frequencies are: 125KHz, 133KHz (also close to other frequencies, such as TI using 134.2KHz). The low frequency tag is typically a passive tag whose operating energy is obtained by inductive coupling from the near field of the radiation of the reader coupling coil. When transmitting data between the low frequency tag and the reader, the low frequency tag needs to be located in the near field region radiated by the reader antenna. The reading distance of the low frequency tag is generally less than 1 meter.
Typical applications for low frequency tags are: animal identification, container identification, tool identification, RFID latching theft (car keys with built-in transponders). International standards related to low frequency tags are: ISO11784/11785 (for animal identification), ISO18000-2 (125-135 kHz). Low-frequency tags come in a variety of appearances. The appearance of low-frequency tags for animal identification is: collar type, ear type, injection type, pill type, etc. Typical applications for animals include cattle and pigeons.
The main advantages of low-frequency tags are: the tag chip generally adopts ordinary CMOS technology, which has the characteristics of power saving and low cost; the working frequency is not restricted by radio frequency control; it can penetrate water, organic tissue, wood, etc.; it is very suitable for close range Identification applications with low speed and low data requirements (eg animal identification).
The disadvantages of low-frequency tags are mainly reflected in the fact that the amount of data stored in tags is small; it can only be applied to low-speed, close-range identification applications; compared with high-frequency tags: the number of tag antennas is higher and the cost is higher;
2. Medium and high frequency band RFID tags
The operating frequency of the medium and high frequency RFID tags is generally 3MHz ~ 30MHz. The typical operating frequency is 13.56 MHz. The RFID tag of this frequency band, from the perspective of radio frequency identification application, works in the same way as the low-frequency tag, that is, it works by inductive coupling, so it should be classified as a low-frequency tag. On the other hand, according to the general division of the radio frequency, its operating frequency band is also called high frequency, so it is often referred to as a high frequency tag. High-frequency RFID tags are also generally passive, and their working energy is the same as that of low-frequency tags. It is also obtained by inductive (magnetic) coupling from the near-field of the coupled coil of the reader. When the tag exchanges data with the reader, the tag must be located in the near field region of the reader antenna radiation. The reading distance of the IF tag is generally less than 1 meter (the maximum reading distance is 1.5 meters).
The basic characteristics of the high frequency standard are similar to the low frequency standard. Due to the increased operating frequency, a higher data transmission rate can be selected. The RFID tag antenna design is relatively simple, and the tag is generally made into a standard card shape. Typical applications include: RFID ticket, RFID ID card, RFID lockout anti-theft (RFID remote control door lock controller), residential property management, building access control system. Relevant international standards are: ISO14443, ISO15693, ISO18000-3 (13.56MHz) and so on.
3. UHF and microwave tags
The RFID tags of the ultra-high frequency and microwave frequency bands are referred to as microwave RFID tags, and the reading distance of the ultra-high frequency tags is large. Its typical operating frequency is: 433.92MHz, 862 (902) ~ 928MHz, 2.45GHz, 5.8GHz. Microwave RFID tags can be classified into active tags and passive tags. In operation, the RFID tag is located in the far field of the radiation field of the reader antenna, and the coupling between the tag and the reader is electromagnetic coupling. The reader antenna radiation field provides RF energy to the passive tag and wakes up the active tag. The reading distance of the corresponding RFID system is generally greater than 1m, typically 4~7m, and the maximum is more than 10m. The reader antennas are generally directional antennas, and only RFID tags within the directional beam range of the reader antenna can be read/written. Due to the increase of reading distance, it is possible to have multiple RFID tags in the reading area at the same time, which raises the need for simultaneous reading of multiple tags, and this demand has become a trend. At present, advanced RFID systems regard multi-label reading problems as an important feature of the system.
UHF tags are mainly used for automatic identification of railway vehicles, container identification, and can also be used in road vehicle identification and automatic toll collection systems. At the current state of the art, passive microwave RFID tags are relatively successful products that are relatively concentrated in the 902~928MHz operating frequency band. 2.45 GHz and 5.8 GHz RFID systems are mostly available in active microwave RFID tag products. Active tags are typically powered by button cells and have a farther reading distance.
The typical characteristics of microwave RFID tags mainly focus on whether passive, wireless read/write distance, whether to support multi-tag reading and writing, whether it is suitable for high-speed identification applications, the transmit power tolerance of readers, the price of RFID tags and readers, etc. . For wirelessly writeable RFID tags, the write distance is typically less than the read distance because the write requires more energy. The data storage capacity of microwave RFID tags is generally limited to 2Kbits. The large storage capacity does not seem to have much significance. From the technical and application point of view, microwave RFID tags are not suitable as carriers for large amounts of data. The function is to identify the item and complete the contactless identification process. Typical data capacity indicators are: 1Kbits, 128Bits, 64Bits, etc. The product RFID code EPC set by the Auto-ID Center has a capacity of 90 Bits.
Typical applications for microwave RFID tags include: mobile vehicle identification, RFID identity cards, warehousing logistics applications, and more. Relevant international standards are: ISO10374, ISO18000-4 (2.45GHz), -5 (5.8GHz), -6 (860-930 MHz), -7 (433.92 MHz), ANSI NCITS256-1999, etc.
At present, the same frequency used in different countries is not the same. At present, UHF used in Europe is 868MHz, and in the United States it is 915MHz. Japan does not currently allow UHF to be used in RF technology. The government also limits its impact on other devices by adjusting the power supply to the reader. Some organizations, such as the Global Business Promotion Council, are encouraging governments to lift restrictions. Label and reader manufacturers are also developing systems that can use different frequency systems to avoid these problems.
Currently in practical applications, the commonly used frequency bands are 13.56MHz, 860MHz ~ 960MHz, 2.45GHz. The short-range RFID system mainly uses LF and HF bands such as 125KHz and 13.56MHz, and the technology is the most mature; the long-distance RFID system mainly uses UHF frequency bands such as 433MHz, 860MHz to 960MHz, and microwave frequency bands of 2.45GHz and 5.8GHz.
China's technology in the design of RFID tag chips in the LF and HF bands is relatively mature. The design technology of the HF band is close to the international advanced level. The RFID chips conforming to ISO14443 Type A, Type B and ISO15693 standards have been independently developed and successfully applied. Traffic card and second-generation ID card and other projects.