How RFID (Radio Frequency Identification) Works

radio-frequency identification (RFID) graphic

How RFID (Radio Frequency Identification) Works

RFID (radio frequency identification) is a form of wireless communication that incorporates the use of electromagnetic or electrostatic coupling in the radio frequency portion of the electromagnetic spectrum to uniquely identify an object, animal or person. Use cases for RFID technology include healthcare, manufacturing, inventory management, shipping, retail sales and home use. Let’s check out how RFID works.

Types of RFID tags

RFID tags are made up of an integrated circuit (IC), an antenna and a substrate. The part of an RFID tag that encodes identifying information is called the RFID inlay.

There are two main types of RFID tags: active RFID and passive RFID. An active RFID tag has its own power source, often a battery. A passive RFID tag, on the other hand, does not require batteries; rather it receives its power from the reading antenna, whose electromagnetic wave induces a current in the RFID tag’s antenna. There are also semi-passive RFID tags, meaning a battery runs the circuitry while communication is powered by the RFID reader.

Low power, embedded non-volatile memory plays an important role in every RFID system. RFID tags typically hold less than 2,000 KB of data, including a unique identifier/serial number. Tags can be read-only or read-write, where data can be added by the reader or existing data overwritten.

The read range for RFID tags varies based on factors including type of tag, type of reader, RFID frequency, and interference in the surrounding environment or from other RFID tags and readers. Generally speaking, active RFID tags have a longer read range than passive RFID tags due to the stronger power source.

RFID frequencies

There are three main types of RFID systems: low frequency (LF), high frequency (HF) and ultra-high frequency (UHF). Microwave RFID is also available. Frequencies vary greatly by country and region.

  • Low-frequency RFID systems range from 30 KHz to 500 KHz, though the typical frequency is 125 KHz. LF RFID has short transmission ranges, generally anywhere from a few inches to less than six feet.
  • High-frequency RFID systems range from 3 MHz to 30 MHz, with the typical HF frequency being 13.56 MHz. The standard range is anywhere from a few inches to several feet.
  • UHF RFID systems range from 300 MHz to 960 MHz, with the typical frequency of 433 MHz and can generally be read from 25-plus feet away.
  • Microwave RFID systems run at 2.45 GHz and can be read from more than 30-plus feet away.

The frequency used will depend on the RFID application, with actual obtained distances sometimes varying considerably from what might be expected. For example, when the U.S. State Department announced it was to issue electronic passports enabled with an RFID chip, it said the chips would only be able to be read from approximately four inches away. However, the State Department was soon confronted with evidence that RFID readers could skim the information from the RFID tags from much farther than 4 inches, some claiming upward of 33 feet away, proving the difference between advertised and actual range can vary immensely.

If read longer ranges are needed, using particular tags with additional power can boost read ranges to 300-plus feet.

RFID frequencies and ranges

RFID applications and use cases

RFID dates back to the 1940s; it was used more frequently in the 1970s. For a long time, however, the high cost of the tags and readers prohibited widespread commercial use. As hardware costs have decreased, RFID adoption has also increased.

The most common RFID application is for tracking and management. This includes pet and livestock tracking, inventory management and asset tracking, cargo and supply chain logistics, and vehicle tracking. RFID can also be used in retail for advertising customer service and loss control; in the supply chain for improved visibility and distribution; and in security situations for access control.

Multiple industries use RFID applications, including healthcare, manufacturing, retail, business and home use.

RFID vs. barcodes

Using RFID as an alternative for barcodes is increasing in use. Among its benefits, RFID can identify individual objects, animals or people without direct line of sight, can identify many items — often a thousand or more — simultaneously, and can scan items anywhere from inches to feet away depending on the type of tag and RFID reader. Read time for RFID tags is typically less than 100 milliseconds.

Barcodes, on the other hand, require direct line of sight and closer proximity than an RFID tag. They also take longer to read, generally ½ second or more per tag. Because barcodes represent a product type versus an individual object represented by an RFID tag, additional information cannot be gleaned from them. In addition, barcodes are not read-write, and because they are printed on the outside of the object are limited in terms of reuse thanks to wear and tear. RFID tags are more rugged and better protected, often in a plastic cover. However, RFID tags cost more than a printed barcode.


Near-field communication (NFC) allows data to be exchanged between devices by using short-range, high-frequency wireless communication technology. NFC combines the interface of a smartcard and reader into a single device.

Radio Frequency ID Near Field Communication
Uni-directional Bi-directional
Range up to 100m Range less than 0.2m
LF/HF/UHF/Microwave 13.56 MHz
Continuous sampling No continuous sampling
Bit rate varies with frequency Up to 424 kbit/s
Power rate varies with frequency <15 milliamperes

RFID challenges

RFID is prone to two main issues: reader collision and tag collision. Reader collision, when a signal from one RFID reader interferes with a second reader, can be prevented by using an anti-collision protocol to make RFID tags take turns transmitting to their appropriate reader.

Tag collision occurs when too many tags confuse an RFID reader by transmitting data at the same time. Choosing a reader that gathers tag info one at a time will prevent this issue.

RFID security and privacy

A common RFID security or privacy concern is that RFID tag data can be read by anyone with a compatible reader. Additionally, tags can often be read after the item leaves the store or supply chain. Tags can also be read without the user’s knowledge, and if the tag has a unique serial number, it can be associated to a consumer. While a privacy concern for individuals, in military or medical settings this can be a national security concern or life-or-death matter.

Because RFID tags do not have a lot of compute power, they are unable to accommodate encryption, such as might be used in a challenge-response authentication system. One exception to this, however, is specific to the RFID tags used in passports, basic access control (BAC). Here, the chip has sufficient compute power to decode an encrypted token from the reader, thus proving the validity of the reader. At the reader, in turn, information printed on the passport is machine-scanned and used to derive a key for the passport. There are three pieces of information used — the passport number, the birth date of the passport holder and the passport’s expiration date — along with a checksum digit for each of the three. Researchers have pointed out that this means passports are protected by a password with considerably less entropy than is normally used in e-commerce, and further that the key is static for the life of the passport, so that once an entity has had one-time access to the printed key information, the passport is readable with or without the consent of the passport bearer until the passport expires. The U.S. State Department, which adopted the BAC system in 2007, additionally has added an anti-skimming material to electronic passports to mitigate the threat of undetected attempts to steal users’ personal information.

RFID standards

There are a number of guidelines and specifications for RFID technology, with the main ones being the International Organization for Standardization (ISO), Electronics Product Code Global Incorporated (EPCglobal) and International Electrotechnical Commission (IEC).

Each radio frequency has associated standards, including ISO 14223 and ISO/IEC 18000-2 for LF RFID, ISO 15693 and ISO/IEC 14443 for HF RFID, and ISO 18000-6C for UHF RFID.

Next-generation RFID use

RFID systems are becoming increasingly used to support internet of things deployments. Combining the technology with smart sensors and/or GPS technology allows sensor data including temperature, movement and location to be wirelessly transmitted.

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