Among these three types of RFID products, passive RFID is the earliest, the most mature and the most widely used. In passive RFID, the electronic tag receives the microwave signal sent by the RFID reader and obtains energy through the electromagnetic induction coil, so that the electronic tag can complete the information exchange in a short time.
Because the power supply system is omitted, the volume of passive RFID products can reach centimeter level or even smaller, with simple structure, low cost, low failure rate and long service life. However, as a cost, the effective identification distance of passive rfid is usually short, and it is usually used for close contact identification. Passive RFID is in lower frequency bands such as 125KHz, 13.56MKHz.
2. active RFID.
Although the development of active RFID technology is not long, it has played an indispensable role in various fields, especially in the expressway electronic toll collection system. Active rfid actively sends signals to RFID readers through external power supply. Its volume is relatively large. But the transmission distance is long and the transmission speed is fast. A typical active rfid tag can be connected with an RFID reader at a distance of 100 meters, and the reading rate is 1700 times per second.
Active RFID mainly works in high frequency bands such as 900mhz, 2.45ghz and 5.8ghz, and has the function of identifying multiple tags at the same time. The long distance and high efficiency of active rfid technology make it indispensable in some applications that require high performance and wide range RFID.
3. semi-active RFID.
Passive RFID has no power supply, but the effective identification distance is too short. Active RFID identification distance is long enough, but it needs external power supply and is huge. Semi-active RFID is the product of this contradiction and compromise. Semi-active RFID is also called low frequency activation trigger technology. Usually, semi-active RFID products are dormant and only supply power to the part where the tag stores data, so the power consumption is low and it can last for a long time.
When a tag enters the identification range of an RFID reader, the reader first activates the tag accurately in a small range with a low-frequency signal of 125khz, and then sends information to it through a 2.4ghz microwave.
In other words, low-frequency signals are used for accurate positioning first, and then high-frequency signals are used for fast data transmission. Usually, the application scenario is to activate semi-active RFID products by placing multiple low-frequency readers at different positions in a large range covered by high-frequency signals. This not only completes the positioning, but also realizes the collection and transmission of information.
Extended data:
Characteristics of RFID:
1. Applicability: RFID technology relies on electromagnetic waves and does not require physical contact between the two parties. This makes it possible to connect directly and complete communication without considering dust, fog, plastic, paper, wood and various obstacles.
2. Efficiency: The reading and writing speed of RFID system is very fast. The typical RFID transmission process is usually less than 100 milliseconds. High-frequency RFID reader can identify and read the contents of multiple tags at the same time, which greatly improves the efficiency of information transmission.
3. Uniqueness: Each RFID tag is unique. Through the one-to-one correspondence between RFID tags and products, the subsequent circulation of each product can be clearly tracked.
4. Simplicity: RFID tag has simple structure, high recognition rate and simple reading equipment. Especially with the gradual popularization of NFC technology on smart phones, every user's mobile phone will become the simplest RFID reader.
Baidu encyclopedia-radio frequency identification technology
Baidu encyclopedia-radio frequency technology