RFID stands for “radio-frequency identification,” It refers to a technology in which a reader captures digital data encoded in RFID tags or smart labels using radio waves. In the same way, as information from a tag or sticker is retrieved by a computer and stored in a database, RFID technology is equivalent to barcoding.

Electromagnetic fields are used in radio-frequency identification to classify and trace tags attached to objects automatically. A wireless transponder, a radio receiver, and a transmitter make up an RFID system.

RFID technology automates data storage, reducing human error and initiative significantly. RFID technology enables tag reading without the need for line-of-sight or item-by-item scanning. RFID readers can read several RFID tags at the same time, which improves performance.


Types of RFID Tags

RFID tags can be grouped based on a range of frequencies they use to communicate and transfer data and information. There are three categories of RFID tags:

  • Low-Frequency LF
  • High-Frequency HF
  • Ultra High-Frequency UHF

Radio Frequency Spectrum

The electromagnetic spectrum is made up of different wavelengths of vibrations caused by electromagnetic radiation. A segment of the electromagnetic spectrum wherein electromagnetic waves can be produced by electrical power fed to an antenna is known as the radio frequency spectrum.

RFID technology is used in systems that include staff monitoring or identification, as well as access control. Today’s cards use a variety of RFID frequency ranges, including 125 kHz low-frequency proximity, 13.56 MHz high-frequency smart cards, and 860-960 MHz ultra-high frequency cards (UHF).

Electromagnetic Spectrum

Low-Frequency LF

Low-Frequency LF RFID systems have higher read times and narrower reading ranges than UHF or HF tags, but their longer wavelength makes them less vulnerable to interference from liquids and metals. They’re mostly used in applications where an RFID sticker is affixed to a metal layer, storing and managing beer kegs or vehicles.

The Low-Frequency LF RFID tags lie between 30 kHz and 300 kHz, with larger wavelengths reaching up to 2400 meters.

Entry monitoring, asset detection, washing, animal recognition, automotive surveillance, vehicle immobilizers, healthcare, and multiple point-of-sale applications (such as Mobil/Exxon SpeedPass) are applications of LF RFID systems.

High-Frequency HF

Inductive coupling design is used in High-Frequency HF RFID tags, which are typically passive and don’t require a power supply or battery. HF RFID tags have a more comprehensive read range and more storage, making them ideal for cataloging library materials or using amusement park tagging wristbands. HF bands have anti-collision features, allowing a single reader to read several tags at the same time.

The HF band lies between 3 MHz to 30 kHz, but it consists of a much slower wavelength than the LF band up to 22 meters only.

High-Frequency HF RFID systems are primarily used in access control applications, data transfer applications, and ticketing applications.

Ultra High-Frequency UHF

The UHF RFID systems cover the spectrum of frequencies from 300 MHz to 30 GHz. Ultra-High Frequency UHF RFID frequency bands are RFID tags that run in this high-frequency range. 433 MHz and 860 to 960 MHz are the most common frequencies used by UHF RFID tags and readers.

The far-field radiative coupling theory, also known as backscatter coupling, is used in these tags. As compared to LF and HF RFID tags, UHF RFID bands have a much longer read range.

Ultra High-Frequency UHF RFID tags are suitable for applications that require reading many objects at once, such as crates of merchandise passing through a factory door or racers crossing a finish line, due to their high data transfer rates.

RFID tags are available in a variety of styles, forms, and sizes. A tag is created to be used for a certain application or group of applications. Tags are divided into four groups based on how they receive power, the frequency at which they run, the protocol they use, and the different functionalities they provide. Now let’s categorize types of RFID tags based on the power source.

Passive RFID Tags

Until they transmit a radio signal from a reader, passive tags are inactive. The reader’s signal is used to flip on the tag and send a data signal back to the reader. The benefits include a wider variety of shapes, sizes, and textures (both inlays and rough tags), as well as a reduced cost per tag and longer operating life.

File monitoring, race scheduling, supply chain management, retail inventory tracking, smart labels, and other technologies use passive tags.

Semi-Passive Tags

Semi-passive tags are also known as semi-active or battery-assisted passive (BAP) tags. They work on the same principles as passive tags, but they have a battery that extends the contact range, tag memory, and in some situations, sensors.

Semi-passive RFID systems or BAP tags are distinguished from passive and active tags by the presence of a battery and the absence of an onboard transmitter, which allows them to accommodate external functionality without expanding read range.

Semi-passive systems are better designed for applications where additional features such as environmental detection are required. The tagged objects must stay within the range of the reader due to these characteristics.

Active RFID Tags

Active RFID systems are comprised of a transmitter (either a transponder or a beacon) and a power supply integrated into a single device. The transmitter is powered by the battery when sending data to an RFID reader. They typically relay data at higher frequencies (850-950 MHz is common), and the tags can be read from distances of up to 100 feet and at faster speeds.

Although new applications for active frequency bands emerge daily, the oil and gas industry, shipping and logistics, transportation, mining, and high-value manufacturing are the most common industries where active RFID tags are used. Active RFID systems are also used for livestock tracking.

Active RFID

Passive vs. Semi-Passive vs. Active RFID

Advantages of Passive RFID:

  • Low Cost
  • Lightweight
  • Less Noise
  • Greater lifetime

Dis-Advantages of Passive RFID:

  • Short Range
  • Low Storage
  • No Sensors
  • Requires Readers

Advantages of Semi-Passive RFID:

  • Medium Range
  • Active Components
  • Moderate Costs
  • Less Noise

Dis-Advantages of Semi-Passive RFID:

  • Requires Readers
  • Limited Lifetime

Advantages of Active RFID:

  • Long Range
  • Low Power Readers
  • More Components
  • Less Interference

Dis-Advantages of Active RFID:

  • High Costs
  • Low Lifetime
  • Noisy
  • Large and Heavy
Passive vs Semi-Passive vs Active RFID Tag

How to Choose Your RFID System

It’s not easy to choose the right tag. It necessitates a detailed understanding of how tags and interrogators operate and the business procedures carried out on the tagged items. Certain conditions must be weighed to select the kind of RFID solution that fits better for a given device, such as:

  • Cost
  • Tag Type
  • Operating Frequencies
  • Tag Size and Materials to be tagged
  • Tag mounting method
  • Read Rates and Range
  • Environmental Conditions