How RF technology works.20mm glass cap Photoresistor

　　Radio Frequency Technology (RF) is the abbreviation of Radio Frequency. The more common applications are Radio Frequency Identification (RFID), often called inductive electronic chips or proximity cards, proximity cards, non-contact cards, electronic tags, electronic barcodes, etc. The principle is that the scanner emits a specific frequency of radio wave energy to the receiver to drive the receiver circuit to send out the internal code, and then the scanner will receive the code. The special feature of the receiver is that it does not use batteries, touches, and swipe cards, so it is not afraid of dirt, and the chip password is the only one in the world that cannot be copied, with high security and long life. RFID has a wide range of applications. Typical applications currently include animal chips, car chip anti-theft devices, access control, parking lot control, production line automation, and material management. There are two types of RFID tags: active tags and passive tags.

　　The basic model of the radio frequency identification system is shown in Figure 8-1.

　　Among them, electronic tags are also called radio frequency tags, transponders, and data carriers; readers are also called reading devices, scanners, communicators, and readers (depending on whether the electronic tags can rewrite data wirelessly). The electronic tag and the reader realize the spatial (non-contact) coupling of the radio frequency signal through the coupling element. In the coupling channel, according to the timing relationship, the energy transfer and the data exchange are realized.

　　There are two types of RF signal coupling between the reader and the electronic tag.

　　(1) Inductive coupling. The transformer model realizes the coupling through the space high frequency alternating magnetic field, which is based on the law of electromagnetic induction, as shown in the figure:

　　Figure 8-1

　　Principles and application areas of radio frequency technology

　　(2) Electromagnetic backscatter coupling: Radar principle model, the emitted electromagnetic wave is reflected after it hits the target, and the target information is carried back at the same time, based on the law of electromagnetic wave propagation in space

　　The inductive coupling method is generally suitable for low- and high-frequency short-range radio frequency identification systems. Typical operating frequencies are: 125kHz, 225kHz and 13.56MHz. The recognition range is less than 1m, and the typical range is 10-20cm.

　　The electromagnetic backscatter coupling method is generally suitable for the long-distance radio frequency identification system of ultra-high frequency and microwave operation. Typical operating frequencies are: 433MHz, 915MHz, 2.45GHz, 5.8GHz. The recognition range is greater than 1m, and the typical range is 3-l0m

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