How does Radio Frequency Identification (RFID) work?

With the development of the Internet of Things, RFID technology is increasingly being applied in industrial settings.The full English name for RFID is "Radio Frequency IDentification," which is translated into Chinese as "無線射頻識別". It is a wireless identification technology born in the 1950s, capable of identifying individuals using radio without contact. According to different radio frequencies, RFID systems can be divided into four types: low frequency, high frequency, ultra-high frequency, and microwave.

Low Frequency System (LF): Systems with RFID radio wave frequencies below 134KHz, following ISO/IEC 18000-2 standards;

High-frequency system (HF): Systems with RFID radio frequency at 13.56MHz, complying with ISO/IEC 15693 (compatible with ISO/IEC 18000-3) and ISO14443 standards;

Ultra-High Frequency System (UF): Systems with RFID radio wave frequencies between 860~960MHz, following ISO/IEC 18000-6B/C standards;

Microwave system: RFID system with a radio frequency of 2.4GHz, following ISO/IEC 18000-4 standard;

An RFID system generally consists of four parts: electronic tags, antennas, readers and writers, and application software.

Electronic tags are similar to barcodes in barcode systems, with an integrated erasable chip used to store information. Depending on whether they carry a battery, electronic tags are divided into active and passive types. Active electronic tags have batteries and can be read at a longer range compared to passive tags;

Antenna: Generally connected to a reader/writer, used to receive/transmit electromagnetic waves;

Reader/Writer: Used to read data from electronic tags and transmit it to the host computer application software system; Some can also write data into electronic tags;

Application software: software systems based on PC or PLC to process data sent by readers and writers;

The RFID system is shown in the figure below:

The working principle of the RFID system is as follows:

The reader and writer transmit electromagnetic waves of a certain frequency outward through their antenna; When the electronic tag enters the operating range of the transmitting antenna, it generates an induced current inside and activates it, so the stored information is sent out through the internal antenna; The reader's antenna receives the carrier signal from the electronic tag and sends it to the reader; The reader and writer demodulate and decode the received signals, then send the processed data to the host computer or PLC processing system.