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How does RFID work?

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Quick answer

RFID uses radio waves to identify objects. A reader sends a signal that powers a tag, which then sends back a unique code. This allows contactless tracking and data capture without line-of-sight, enabling fast inventory, access control, and supply chain management.

RFID (Radio Frequency Identification) works by using radio waves to automatically identify and track tags attached to objects. A reader emits a radio signal that powers a tag, which then transmits back its unique identifier.

Step by step

  1. A reader emits a continuous radio signal at a set frequency, forming an electromagnetic field.
  2. When an RFID tag enters this field, its antenna captures the radio waves and converts them into electrical energy.
  3. The tag's microchip uses this energy to retrieve its stored unique identifier and other data.
  4. The tag modulates the radio waves by changing how it reflects them, encoding the identifier in the signal.
  5. The reader receives the reflected signal, demodulates it, and extracts the tag's data.
  6. The reader sends the data to a connected computer system, which processes it for tracking or authentication.

Key things to understand

  1. An RFID system consists of a reader, a tag, and a computer system that processes the data.
  2. The reader emits a radio signal at a specific frequency, creating an electromagnetic field.
  3. When a tag enters this field, it harvests energy from the radio waves to power its internal chip.
  4. The tag's chip then modulates the radio waves with its unique identification number and sends it back.
  5. The reader captures this reflected signal, decodes it, and passes the ID to a database for action.

Labelled diagram

  1. Reader

    Emits radio waves and creates an electromagnetic field.

  2. Tag

    Enters field, harvests energy to power its chip.

  3. Signal

    Tag modulates waves with its unique ID.

  4. Reader

    Receives and decodes the reflected signal.

  5. Database

    Stores and processes the ID for action.

How RFID Works

Real-world examples

  • In retail stores like Walmart, RFID tags on clothing and products allow employees to scan entire shelves at once for inventory.
  • Library books often contain RFID tags so librarians can check out multiple books instantly and prevent theft.
  • Contactless payment cards like credit cards use RFID technology to transmit payment information when tapped on a reader.
  • Livestock farmers fit animals with RFID ear tags or implanted microchips to track their health and movement from birth to market.

Common mistake

✗ Myth: RFID tags contain batteries and constantly transmit signals.

✓ Fact: Most RFID tags are passive and have no battery; they only transmit when powered by a reader's radio waves. Active tags with batteries exist but are less common.

People also ask

What is RFID used for?
RFID is used for automated tracking and identification in many fields. Common applications include inventory management in retail, access control for buildings, contactless payments, passport verification, and tracking livestock or assets in supply chains.
How does an RFID tag get power?
Passive RFID tags get power from the radio waves emitted by the reader. The tag's antenna captures the electromagnetic energy and converts it into electricity to power the chip, which then sends back its data.
What is the range of RFID?
RFID range varies by frequency and power. Low-frequency tags work up to about 10 cm, high-frequency up to 1 meter, and ultra-high-frequency can reach 12 meters or more. Active tags with batteries can transmit over 100 meters.
What is the difference between active and passive RFID?
Passive tags have no battery and rely on the reader's signal for power, making them cheap and small. Active tags contain a battery, allowing them to transmit over longer distances and store more data, but they are larger and more expensive.
Can RFID tags be read through walls or other materials?
RFID signals can penetrate some materials like plastic, paper, and wood, but are blocked by metals and liquids. Low-frequency systems cope better near liquids and metal, while higher-frequency systems, especially UHF, are more affected by these materials.
How is RFID different from barcodes?
Barcodes require line-of-sight and are read one at a time, while RFID tags can be read without direct visibility and multiple tags can be read simultaneously. RFID also allows data to be updated, whereas barcodes are static.
Is RFID safe for humans and pets?
RFID uses low-power radio waves that are generally considered safe and do not cause harm. The levels are much lower than those from mobile phones, and there is no evidence of health risks from normal exposure.

Part of the guide: How the Internet Works →