Radio Frequency Identification is a wireless communication technology that can identify a specific target and read and write related data through radio signals without the need for mechanical or optical contact between the identification system and the specific target.
Radio signals transmit data from a tag attached to an item through an electromagnetic field tuned to a radio frequency to automatically identify and track that item. Some tags can get energy from the electromagnetic field emitted by the identifier during identification, and do not need batteries; there are also tags that have their own power supply and can actively emit radio waves (electromagnetic fields tuned to radio frequencies). Tags contain electronically stored information and can be identified within a few meters. Unlike barcodes, RFID tags do not need to be in line of sight of the reader and can be embedded within the object being tracked.
RFID consists of three parts:
1. Tag: RFID tag is a passive part of the RFID system, usually composed of a chip and an antenna. The chip on the tag is used to store data, and when it receives the radio frequency signal sent by the RFID reader, it receives and returns the data through the antenna. RFID tags can have different forms according to application requirements, such as stickers attached to commodities, embedded tags embedded in products, or RFID tags in the form of cards.
RFID tags use electronic technology to store messages on a permanent storage area with a tiny radio wave transceiver in the middle of the tag. The reader sends out a coded radio signal to "inquire" the radio frequency tag, and the tag sends out its own identification message to reply after receiving the signal. The identification message can be the serial number of the label itself, or other information about the product, such as material number, production date, batch number or batch number, or other specific information.
The radio frequency identification tag has at least two parts: one is an integrated circuit to store and process information, modulate and demodulate a radio frequency signal, collect DC power from the signal transmitted from the reader, etc.; the other is an antenna to receive the signal transmission signal. Tag information is stored in non-volatile memory. RFID tags include a logic integrated chip or a programmed or programmable data processor to process and transmit sensor data, respectively.
2. Reader: A device that reads tag information. The reader is the active part of the RFID system, which is used to send radio frequency signals to activate the RFID tags and read the data stored in the tags. The reader sends the RFID signal through its antenna and receives the return signal from the tag. The reader can be connected to a computer or other system in order to transmit the read RFID tag data to the background database for processing and analysis.
The reader is a device that reads out the information in the tag, or writes the information that the tag needs to store into the tag. Depending on the structure and technology used, the reader can be a read/write device, which is the information control and processing center of the RFID system. When the RFID system is working, the reader sends radio frequency energy in an area to form an electromagnetic field, and the size of the area depends on the transmission power. The tags in the coverage area of the reader are triggered, send the data stored in it, or modify the data stored in it according to the instruction of the reader, and can communicate with the computer network through the interface.
3. Antenna: transmits radio frequency signals between the tag and the reader.
Ⅱ. Classification application of RFID
Defining the working frequency of RFID products, there are different products that meet different standards in the frequency range of low frequency, high frequency and very high frequency, and RFID products in different frequency bands will have different characteristics. There are two types of sensors, passive and active.
1. Low frequency RFID
RFID technology was first widely used and promoted in low frequency (from 125kHz to 134kHz). This frequency mainly works through inductive coupling, that is, there is a transformer coupling effect between the reader coil and the inductor coil, and the voltage induced in the inductor antenna by the action of the reader's alternating field is rectified and can be used as a power supply voltage.
The general operating frequency of the sensor working at low frequency is from 120kHz to 134kHz, and the operating frequency of TI is 134.2kHz. The wavelength of this frequency band is about 2500m;
Readers working at low frequencies do not have any special licensing restrictions worldwide;
Compared with RFID products in other frequency bands, the data transmission rate in this frequency band is relatively slow;
In addition to the influence of metal materials, generally low frequencies can pass through items of any material without reducing its reading distance.
Application of marathon running system; automatic parking lot charging and vehicle management system; application of automatic refueling system; animal husbandry management system; application of car anti-theft and keyless door opening system, etc.
2. High frequency RFID
High-frequency sensors at this frequency no longer need coils to be wound, and antennas can be made by etching or printing. Sensors generally work by means of load modulation. That is, the voltage on the antenna of the reader is changed by turning on and off the load resistance on the sensor, and the amplitude modulation of the antenna voltage is realized by the remote sensor.
The working frequency is 13.56MHz, and the wavelength of this frequency is about 22m;
The data transmission rate is faster than low frequency, and the price is not expensive;
Sensors are generally in the form of electronic tags;
The wavelength of this frequency can pass through most materials except metal materials, but it tends to reduce the reading distance. The sensor needs to be a distance away from the metal;
The system has anti-collision features and can read multiple electronic tags at the same time.
Management of intelligent shelves; application of library management system; management and application of medical logistics system; management and application of hotel door locks, etc.
3. VHF RFID
VHF systems transmit energy through electric fields. The energy of the electric field does not drop very fast, but the read area is not well defined. The reading distance of this frequency band is relatively long, and the passive range can reach about 10m. It is mainly realized by means of capacitive coupling.
The antenna of the electronic tag is generally long and tag-shaped. The antenna has two designs of linear polarization and circular polarization to meet the needs of different applications;
In this frequency band, the global definition is not quite the same - the frequency defined in Europe and parts of Asia is 868MHz, the frequency band defined in North America is between 902MHz and 905MHz, and the frequency band proposed in Japan is between 950MHz and 956MHz. The wavelength of this frequency band is about 30cm;
With high data transmission rate, a large number of electronic tags can be read in a short time;
Radio waves in the VHF band cannot pass through many materials, especially water, dust, fog and other suspended particles. Compared with high-frequency electronic tags, electronic tags in this frequency band do not need to be separated from metals.
The management and application of air parcels; the management and application of railway parcels; the application of large-scale personnel entry and exit management; the management and application of supply chain, etc.
4. Active RFID technology
It is a variant of RFID technology, which is different from traditional passive RFID technology. In active RFID systems, RFID tags are not passive, but have active energy and communication functions.
In an active RFID system, a battery or other energy source is installed inside the RFID tag, enabling the tag to autonomously generate radio frequency signals and communicate without relying on external radio frequency signal activation. In this way, the active RFID tag can communicate with the reader within a longer distance, and has a stronger radio frequency signal transmission capability.
Since the active tags themselves generate radio frequency signals, active RFID systems can communicate over long distances, typically hundreds of meters.
Since the active tag has an independent energy supply, a larger-capacity memory can be integrated inside the chip, and more data information can be stored.
Active tags have high radio frequency signal transmission capabilities, can penetrate obstacles and transmit signals over a long distance, making communication more stable and reliable.
5. Passive RFID technology
It is a common RFID technology and corresponds to active RFID technology. In the passive RFID system, the RFID tag is passive and does not have the ability to generate radio frequency signals independently. It needs to rely on an external RFID reader to send radio frequency signals to activate and transmit data.
When a passive RFID tag is in the RF field of an RFID reader, the reader will send a radio frequency signal. This radio frequency signal contains energy. When the radio frequency signal meets the antenna of a passive RFID tag, the tag will draw energy from it and use this energy to activate the tag. Once a passive RFID tag is activated, it transmits back the data stored within the tag. The tag returns data by changing the characteristics of its own antenna (such as reflection, impedance, etc.), and these changes will be detected and decoded by the reader to read the information in the tag.
Since passive RFID tags do not require a built-in battery or active energy source, they are low cost and suitable for large-scale applications.
Passive tags are activated by the radio frequency signal of the reader and do not generate radio frequency signals spontaneously, so they have a longer service life in scenarios that do not require active communication.
Ⅲ.Types of RFID tags
Active tags, also known as active tags, have a built-in battery, which can use their own power to form an effective active area around the tag, actively detect whether there is a calling signal emitted by a reader around, and send its own data to the reader.
The active tag itself has an internal power supply, which is used to supply the power required by the internal IC to generate external signals. Generally speaking, active tags have a longer reading distance and can accommodate larger memory capacity, which can be used to store some additional messages sent by the reader. The difference between active and semi-passive tags is that active tags can actively transmit the memory data of the internal tag to the reader at any time by means of internal power.
Passive tags have no internal power supply, and their internal integrated circuits are driven by received electromagnetic waves emitted by RFID readers. When the tag receives a signal of sufficient strength, it can send data to the reader.
Because passive tags have the advantages of low price, small size, and no power supply. Currently, the RFID tags used in the market are mainly passive.
Passive RFID tags obtain energy from the electromagnetic waves emitted by the reader, and return the corresponding backscattered signal to the reader. However, in the environment of attenuation of the propagation path, the reading distance of the tag is limited.
Unlike passive tags, semi-passive tags have built-in batteries or other active energy sources, which can autonomously generate radio frequency signals to activate tags. Without the activation of radio frequency signals from an external RFID reader, the tag can transmit radio frequency signals by itself, making it in a dormant or waiting state.
When the semi-passive tag is activated by the radio frequency signal of the external RFID reader, the tag will use the energy generated by the built-in battery to enhance the radio frequency signal transmission capability in order to communicate with the reader. During the communication process, data transmission is performed between the tag and the reader to realize reading and writing of tag information.
The semi-passive tag enhances the radio frequency signal transmission capability through the built-in battery, making its communication distance and reliability higher than that of the pure passive tag. Compared with traditional passive tags, semi-passive tags can accommodate larger memory for storing more data information.
Ⅳ. Features of RFID
1. Applicability: RFID technology relies on electromagnetic waves and does not require physical contact between the two parties. This allows it to establish a connection regardless of dust, fog, plastic, paper, wood, and various obstacles and complete communication directly.
2. Multi-label identification: The RFID system can identify multiple labels at the same time, realizing the parallel identification of multiple labels. This makes RFID technology advantageous in large-scale object identification and fast data processing.
3. Low cost: For passive RFID technology, the manufacturing cost of RFID tags is relatively low, making large-scale applications possible.
4. Efficiency: The reading and writing speed of the RFID system is extremely fast, and a typical RFID transmission process is usually less than 100 milliseconds. High-frequency RFID readers can even identify and read the contents of multiple tags at the same time, which greatly improves the efficiency of information transmission.
5. Automatic identification: RFID technology can realize automatic identification and tracking of objects. As long as the object has an RFID tag, when the tag meets the reader, the data will be transmitted automatically without manual intervention.
6. Uniqueness: Each RFID tag is unique. Through the one-to-one correspondence between RFID tags and products, the follow-up circulation of each product can be clearly tracked.
7. Simplicity: The structure of RFID tags is simple, the recognition rate is high, and the required reading equipment is simple. Especially with the gradual popularization of NFC technology on smart phones, every user's mobile phone will become the simplest RFID reader.
Ⅴ. RFID technology and performance parameters
RFID tags are the key to current RFID technology. RFID tags can store a certain amount of information and have a certain information processing function. The reading and writing equipment can exchange information with the tag through radio signals at a certain data transmission rate. The working distance can vary from several centimeters to 1 kilometer according to the technology used.
The external dimensions of the identification tag are mainly determined by the antenna, and the antenna depends on the operating frequency and the requirements for the working distance. There are four common tags (by radio frequency): low frequency tags (125 or 134.2 kHz), high frequency tags (13.56 MHz), UHF tags (868~956 MHz) and microwave tags (2.45 GHz). Given that no mechanical or optical contact needs to be created between the tag and the read/write device, cryptography is set to play an increasingly important role in the overall RFID technology landscape.
The infrastructure of RFID technology includes:
1. Radio frequency identification tags, also known as radio frequency tags and electronic tags, are mainly composed of large-scale integrated circuit chips with identification codes and transceiver antennas. At present, they are mainly passive types. The power used is taken from the energy in the radio waves received by the antenna.
2. Radio frequency identification reading and writing equipment, also known as RFID reader or RFID reader, is one of the main components of the RFID system. Used to communicate with RFID tags, activate tags and read or write data in them. RFID reading and writing equipment transmits radio frequency signals through radio frequency antennas to activate RFID tags. This process is similar to waking up an RFID tag from a sleep or standby state for data interaction.
Compared with barcode technology, radio frequency category technology has many advantages, such as:
RFID technology is faster than barcode technology. RFID tags do not need to be directly aligned with the reader and can be identified without line of sight, thus enabling faster data collection.
RFID tags have a larger storage capacity and can store more data information, while barcodes can only store limited data.
RFID technology can read multiple tags at the same time to achieve parallel identification of multiple tags, while barcode technology usually needs to scan each barcode one by one.
RFID tags have a larger storage capacity and can store more data information, while barcodes can only store limited data.
Ⅵ. The development trend of RFID
1. Miniaturization and integration: RFID tags and read-write equipment will become more and more miniaturized and integrated to adapt to more application scenarios. Miniaturized RFID tags can be easily embedded in objects or attached to surfaces, making tag deployment more flexible and convenient.
2. High frequency: Compared with the low frequency system, the UHF radio frequency identification system has the advantages of longer recognition distance, faster data exchange speed, higher forgery difficulty, stronger anti-interference ability to the outside world, and small size. With the reduction of manufacturing costs and the further improvement of high frequency technology, the application of UHF system will be more extensive.
3. Multifunctional tags: Future RFID tags will have more functions, not only for object identification and data transmission, but also for integrating sensors to monitor and collect environmental parameters such as temperature, humidity, and pressure, so as to meet more complex needs.
4. Passive radio frequency: Although the current RFID technology is mainly based on active and semi-active methods, passive radio frequency technology is also gradually developing. In the future, passive RFID technology may achieve longer identification distances and wider applications through more efficient energy collection and transmission methods.
5. Multifunctionality: With the continuous improvement and popularization of mobile computing technology, the development trend of the design and manufacture of radio frequency identification readers will be multi-functional, multi-interface, multi-standard, and develop in the direction of modularization, miniaturization, portable, and embedded; at the same time, multi-reader coordination and networking technology will become one of the future development directions.