What is RFID and how it works?

What is RFID?

RFID(radio frequency identification), which is a non-contact automatic identification technology. It can automatically detect the target object and obtains the data through radio frequency signals. The identification work does not require manual intervention and can work in various harsh environments. RFID technology can identify high-speed moving objects and multiple RFID tags at the same time.

What are the three essential elements for a RFID system?

A complete RFID system consists of 3 components:

RFID Reader: it communicated with RFID tags through RFID antenna, and it can read write RFID tag’s EPC.

handheld UHF RFID reader long-range-uhf-rfid-fixed-reader

                                                                                                                    Handheld RFID Reader                                 Fixed RFID Reader

According to the appearance form, there are two type of RFID readers:

  • Fixed RFID Reader
  • Hanheld RFID Reader

According to frequency range, there are 5 type of RFID readers:

  • LF(Low Frequency): 125K RFID reader
  • HF(High Frequency): 13.56mhz RFID reader
  • UHF(Ultra High Frequency): 840-960mhz RFID reader
  • 2.4G active RFID Reader
  • 5.8G RFID Reader

RFID Tags: Composed of coupling elements and chips, each RFID tag has a global unique EPC. It is usually attached to the  target object for identification.

865-928MHz-Small-Size-UHF-RFID(2) alien 9662 uhf rfid inlay (1) uhf rfid on metal tags

There are 3 type of RFID tags:

Passive RFID tags

Passive RFID tags have no battery inside. Its internal integrated circuit is driven by the received electromagnetic waves, which are emitted by the RFID reader. When the tag receives strong signal, it can send data to the reader. The data includes not only the EPC (Unique ID), but also the data pre-entered in the EEPROM in the tag.

Semi passive RFID tags

Generally speaking, the antenna of a passive tag has two tasks: first: receiving the electromagnetic waves emitted by the reader to drive the tag IC; second: when the tag returns a signal, it needs to be switched by the impedance of the antenna to generate 0 Change with 1. The problem is that if you want to have the best return efficiency, the antenna impedance must be designed to be “open and short”, which will completely reflect the signal and cannot be received by the tag IC. The semi-active tag is to solve this problem.

The semi-active tag is similar to the passive tag, but it has a small battery, and the power can drive the tag IC to make the IC work. The advantage of this is that the antenna can be used as a return signal without taking care of the task of receiving electromagnetic waves. Compared with the passive type, the semi-active type has a faster response speed and better efficiency.

Active RFID tags

Unlike passive and semi-passive tags, the active tag itself has an internal power supply to supply the power required by the internal IC to generate external signals. Generally speaking, active tags have a longer reading distance and a larger memory capacity, which can be used to store some additional information sent by the reader.


RFID Antenna: An antenna is a transducer that transforms a guided wave propagating on a transmission line into an electromagnetic wave propagating in an unbounded medium (usually free space), or vice versa. A component used in a radio device to transmit or receive electromagnetic waves.

uhf rfid antenna

There are several type of  RFID antennas:

Circular polarized RFID antenna: the electromagnetic field of the circularly polarized antenna is emitted as a spiral beam

circular polarized rfid antenna

Linear polarized RFID antenna: the electromagnetic wave emitted by the reader antenna of the linear polarization antenna is linear, and its electromagnetic field has strong directivity

linear polarized rfid antenna

Directional RFID antenna: Directional antennas show radiation in a certain angular range on the horizontal pattern, which has feature of directionality

directional rfid antenna

Onmi directional rfid Antenna: An omnidirectional antenna, which shows uniform radiation in 360° on the horizontal pattern, which is commonly referred to as non-directional.

omni directional rfid antenna

RFID Software: Software runs on PC that developed by the RFID hardware company.

How RFID Works?

RFID technology is not complicated: when the rfid tag is within the RFID reader’s reading range, it receives the radio signal that sent by the reader, and uses the energy obtained by the induced current to send out the data stored in the chip, or the activ tag sends a certain frequency signal to reader. After the reader reads and decodes the signal, it will send to the central information system for data processing.

What are typically RFID applications?

  • RFID asset tracking
  • RFID Inventory management
  • RFID Warehouse management
  • Access control
  • RFID jewelry management
  • RFID Retail Management
  • RFID race timing
  • RFID logistics tracking
  • RFID animal tracking
  • RFID healthcare management
  • RFID Vehicle tracking


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