RFID System

RFID system have basically two components.

  1. RFID Tag
  2. RFID Reader



An RFID tag is an electronic tag that exchanges data with an RFID reader via radio waves. Generally, RFID tags are made up of two main parts.

  • The first is a transponder (Radio) antenna, which receives and transmits radio frequency (RF) waves.
  • The second is an integrated circuit (IC) (microchip), which is used for processing and storing data, as well as modulating and demodulating the radio waves received/sent by the antenna. This tag carries 12 unique numbers.


Tag antennas (circular or rectangular in general) collect energy and energies the chip to turn the chip on. Generally, the larger the tag antenna’s area and further it should be in the reading range, the more energy it will be able to collect toward the tag chip. In simple terms, the tag antenna not only catches the wave from the reader to supply energy for the tag operation but also transmits the wave carrying the information stored in the tag.

RFID Tag Internal

Tag is also made up of a protecting/shielding material that holds the pieces together and shields them from various environmental situations.

The protective material usually depends on the application. For example, student ID badges containing RFID tags are typically made from long-lasting plastic, and the tag is embedded between the films of plastic. RFID tags come in different shapes and sizes. Tags can be attached to many things like student ID cards, animals like cows, buffalo, vehicles, clothes in malls, Shoes etc.

There are two types of RFID tags.

  • Passive Tags
  • Active Tags


These tags are mostly used, as they are smaller in size, easy to handle and cheap. Passive tags “powered up” by the RFID reader to transmit data.

Passive tags are comprised of three elements: an antenna, an integrated circuit (IC) or chip, and a substrate. The data or information is stored in an RFID chip. Depending on its design, the chip may be read-write (RW) or write-once, read-many (WORM) or read-only (RO). Typically, RFID chips carry 12 bytes of memory (96Bits).

A passive tag is activated by the radio frequency (RF) scan (signal) of the reader. RF signal (a form of energy) induces electrical current which is small but enough for transmission of an ID number stored in a chip.


Unlike passive tags, active tags need an on-board power supply (e.g., a battery), which enables them to transmit data at all times.

Active tags also have both a microchip and an antenna. The chip of active RFID tags, are usually bigger in size and have greater abilities than the RFID chips of passive tags.


RFID readers are used to read data or unique ID information from RFID tags. This data or information is unique for every single TAG which cannot be copied.

At whatever time RFID tags come closer to its range (typically 10 cm for EM18 module), the RFID reader module reads its unique ID and transmits it serially to the microcontroller. RFID reader has a transceiver antenna mounted on it.

This module can connect to any microcontroller based device which has UART communication or RS232. It gives UART/Wiegand26 output. Working frequency compatible with this module is 125 KHz of RFID tags.


Reader antenna converts electrical current into electromagnetic waves which are then radiated into space and can be received by the antenna of RFID tag. Then tag processes and returns electromagnetic waves into space, these waves contain tag information (i.e. its unique ID) which is received by the antenna of the RFID reader module and the reader converts these waves back to electrical current. This can be processed and decodes the data.

RFID system can operate on different frequencies like Ultra High Frequency (UHF) or High Frequency (HF) or Low Frequency (LF). Therefore, RFID tags can also distinguish in terms of the frequencies on which they operate.


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