Radio-frequency Identification (RFID)

Radio-frequency Identification (RFID)

the 2 main physical elements of a RFID tag: Microchip and Integrated Antenna
Figure 3: the 2 main physical elements of a RFID tag: Microchip and Integrated Antenna

A RFID uses electromagnetic fields to automatically identify and track tags attached to objects. The tags contain electronically-stored information. Passive tags collect energy from a nearby RFID reader’s interrogating radio waves.

Active tags have a local power source (such as a battery) and may operate hundreds of meters from the RFID reader.
One of the main difference and benefit compared to barcodes is that the tag don’t need to be within the line of sight of the reader, so it may be embedded in the tracked object.

RFID tags are used in many industries:

  • a RFID tag attached to an automobile during production can be used to track its progress through the assembly line;
  • RFID-tagged pharmaceuticals can be tracked through warehouses;
  • implanting RFID microchips in livestock and pets allows for positive identification of animals.


The following video shows how this technology works:

Elements of RFID systems

Tags and smart labels

They consist of an integrated circuit and an antenna. The tag is composed of a protective material that holds the pieces together and protect them from environmental conditions. The protective material depends on the application: employee ID badges containing RFID tags, for example, are typically made from durable plastic, and the tag is embedded between the layers of plastic.

RFID tags can be either passive or active:

  • Passive tags are the most used, as they are smaller and less expensive to implement. Passive tags must be “powered up” by the RFID reader before they can transmit data;
  • Unlike passive tags, active RFID tags have an onboard power supply (e.g., a battery), thereby enabling them to transmit data at all times.


A RFID reader transmits an encoded radio signal to interrogate the tag. The RFID tag receives the message and then responds with its identification and other information. This may be only a unique tag serial number, or may be product-related information such as a stock number or batch number, production date, or other specific information.

RFID systems can be classified by the type of tag and reader:

  • An Active Reader Passive Tag (ARPT) system has an active reader, which transmits interrogator signals and also receives authentication replies from passive tags.
  • An Active Reader Active Tag (ARAT) system uses active tags awoken with an interrogator signal from the active reader. A variation of this system could also use a Battery-Assisted Passive (BAP) tag which acts like a passive tag but has a small battery to power the tag’s return reporting signal.


Signaling between the reader and the tag is done in several different ways, depending on the frequency band used by the tag, which also depends on the application. Here some frequency band are listed. Generally, the most common are:

  • Low frequency, or LF, (125 – 134 kHz)

    characterized by low data speed, low range (few cm) and long wave-length, are better able to penetrate thin metallic substances. Additionally, LF RFID systems are ideal for reading objects with high-water content, such as fruit or beverages. Typical LF RFID applications include access control and animal tagging

  • High frequency, or HF, (13.56 MHz)

    characterized by moderate data speed, mid range (up to about 1 m). High-frequency tags work fairly well on objects made of metal and can work around goods with medium to high water content. Typical HF RFID applications include tracking library books, patient flow tracking, and transit tickets.

  • Ultra-high frequency, or UHF, (433, and 860-960 MHz)

    UHF frequencies typically offer much better read range (inches to 50+ ft. depending on the RFID system setup) and can transfer data faster (i.e. read many more tags per second) than low- and high-frequencies. However, because UHF radio waves have a shorter wavelength, their signal is more likely to be attenuated (or weakened) and they cannot pass through metal or water. Due to their high data transfer rate, UHF RFID tags are well suited for many items at once, such as boxes of goods as they pass through a dock door into a warehouse or racers as they cross a finish line. Also, due to the longer read range, other common UHF RFID applications include electronic toll collection and parking access control.

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