From the application concept, the working frequency of the electronic tag is also the working frequency of the RFID system, which is one of its most important features.
There is no doubt that the frequency of operation of electronic tags is one of its most important features. The working frequency of the electronic tag not only determines the working principle of the RFID system (inductive coupling or electromagnetic coupling), the recognition distance, but also determines the difficulty of the electronic tag and the reader and the cost of the device.
Electronic tags that work in different frequency bands or frequencies have different characteristics. The frequency bands or frequencies occupied by RFID applications are internationally recognized as being located in the ISM band. Typical operating frequencies are: 125kHz, 133kHz, 13.56MHz, 27.12MHz, 433MHz, 902~928MHz, 2.45GHz, 5.8GHz, etc.
1. Low frequency electronic tag
Low-band electronic tags, referred to as low-frequency tags, operate at frequencies ranging from 30kHz to 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, electronic 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 electronic tags
The operating frequency of the medium and high frequency electronic tags is generally 3MHz ~ 30MHz. The typical operating frequency is 13.56 MHz. The electronic 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.
Therefore, it should be classified as a low frequency tag class. 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 electronic 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).
Since the high-frequency tag can be easily formed into a card shape, typical applications include: electronic ticket, electronic ID card, electronic latching anti-theft (electronic remote control door lock controller) and the like. Relevant international standards are: ISO14443, ISO15693, ISO18000-3 (13.56MHz) and so on.
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 electronic tag antenna design is relatively simple, and the tag is generally made into a standard card shape.
3. UHF and microwave tags
The ultra-high frequency and microwave frequency electronic tags, referred to as microwave electronic tags, have typical operating frequencies of 433.92 MHz, 862 (902) to 928 MHz, 2.45 GHz, and 5.8 GHz. Microwave electronic tags can be classified into active tags and passive tags. In operation, the electronic 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 electronic 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 electronic 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.
At the current state of the art, passive microwave electronic 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 semi-passive microwave electronic label products. Semi-passive tags are typically powered by button batteries and have a farther reading distance.
The typical characteristics of microwave electronic 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 electronic tags and readers, etc. . For wirelessly writeable electronic tags, the write distance is typically less than the read distance because the write requires more energy.
The data storage capacity of microwave electronic 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 electronic 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 electronic code EPC set by the Auto-ID Center has a capacity of 90 Bits.
Typical applications for microwave electronic tags include: mobile vehicle identification, electronic identification cards, warehousing logistics applications, electronic latching theft (electronic remote door lock controllers), 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 and so on.
According to the above description, the electronic tags can be listed as follows:
Cable Charging Night Lights, Charging Bedside lamp, Charging Night Light, Bulid-in Battery night light
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