RFID (Radio Frequency Identification: Radio Frequency Identification)), commonly known as "RFID tag", is a non-contact automatic identification technology, which automatically identifies the target object and obtains the relevant data through the radio frequency signal. The identification work does not need human intervention, and the main function is to write and read the data. It consists of a label, a reader and a data transmission and processing system. According to the power supply mode of its tag, radio frequency identification technology can be divided into three categories, namely passive RFID, active RFID, and semi-active RFID. At present, passive electronic tags account for 80% of the market, while passive electronic tags account for less than 20%, so what is the difference and relationship between active tags and passive tags? Let's take a look at it with the editor.
1. Passive RFID. Among the three types of RFID products, passive RFID appears the earliest and the most mature, and it is also the most widely used. In the passive RFID, the electronic tag completes the information exchange by receiving the microwave signal transmitted by the radio frequency identification reader and obtaining the energy through the electromagnetic induction coil to power itself briefly. Because the power supply system is omitted, the volume of passive RFID products can reach the order of centimeters or even smaller, and it has the advantages of simple structure, low cost, low failure rate and long service life. But as a cost, the effective recognition distance of passive RFID is usually short, and it is generally used for close contact recognition. Passive RFID mainly works in low frequency band 125KHz, 13.56MKHz and so on. Its typical applications include: bus card, second-generation ID card, canteen meal card and so on.
2. Active RFID. The rise of active RFID is not long, but it has played an indispensable role in various fields, especially in the electronic toll collection system of expressway. The active RFID is powered by an external power supply and actively sends a signal to the radio frequency identification reader. Its volume is relatively large. But it also has a longer transmission distance and higher transmission speed. A typical active RFID tag can establish a connection with an RFID reader at a distance of 100 meters, and the reading rate can reach 1700read/sec. Active RFID mainly works in higher frequency bands such as 900MHz, 2.45GHz, 5.8GHz and so on, and has the function of identifying multiple tags at the same time. Because of its long-distance and high efficiency, active RFID is indispensable in a wide range of radio frequency identification applications that require high performance.
3. Semi-active RFID. Passive RFID does not supply power itself, but the effective identification distance is too short. The identification distance of active RFID is long enough, but it needs external power supply and its volume is large. Semi-active RFID is the product of compromise for this contradiction. Semi-active RFID is also called low frequency activation trigger technology. In general, semi-active RFID products are dormant and only supply power to the part of the label that holds the data, so it consumes less power and can be maintained for a long time. When the tag enters the identification range of the radio frequency identification reader, the reader first uses the 125KHz low frequency signal to accurately activate the tag in a small range to make it enter the working state, and then transmits information to it through 2.4GHz microwave. In other words, first use the low-frequency signal to locate accurately, and then use the high-frequency signal to transmit data quickly. Its common application scenario is: in a large area covered by a high-frequency signal, multiple low-frequency readers are placed in different locations to activate semi-active RFID products. This not only completes the positioning, but also realizes the collection and transmission of information.
1.Active RFID tag.
Active RFID tags are powered by built-in batteries, and different tags use different numbers and shapes of batteries.
Advantages: the distance between the active RFID tag and the RFID reader can reach tens of meters, even up to hundreds of meters.Disadvantages: large size, high cost, service time is limited by battery life.
2. Passive RFID tag.
The passive RFID tag does not contain a battery, and its power is obtained from the RFID reader. When the passive RFID tag is close to the RFID reader, the antenna of the passive RFID tag converts the received electromagnetic wave energy into electrical energy, activates the chip in the RFID tag, and sends the data in the RFID chip.Advantages: small size, light weight, low cost, long life, can be made into flakes or buckles and other different shapes, used in different environments.Disadvantages: because there is no internal power supply, the distance between passive RFID tags and RFID readers is limited, usually within a few meters, which generally requires high-power RFID readers.
The working principle.
1. The active electronic tag means that the energy of the label is provided by the battery, and the battery, memory and antenna constitute the active electronic tag, which is different from the activation mode of passive radio frequency and sends out information by setting the frequency band before the battery is replaced.
2. The performance of passive rfid tags is greatly affected by tag size, modulation form, circuit Q value, device power consumption and modulation depth. Passive RF tag 1024bits memory capacity, ultra-wide working frequency band, not only in line with the relevant industry regulations, but also flexible development and application, can read and write multiple tags at the same time. Passive RF tag design, no battery, memory can be repeatedly erased more than 100000 times.