Radio Frequency Identification (RFID): Definitions

(some of the of terms used in RFID technology)

low-frequency tags
1. From 30 kHz to 300 kHz.

Low-frequency tags typical operate at 125 kHz or 134 kHz. The main disadvantages of low-frequency tags are they have to be read from within three feet and the rate of data transfer is slow.

They are less subject to interference than UHF tags.

2. Tags that operate at a frequency as low as 30 KHz or as high as 300 KHz, but most often at 125 KHz.

They can be read at no more than three feet and the data transfer rate is slow. This type of tag is widely used in retailing because it is relatively inexpensive.

medium-frequency tags
Tags that operate at a frequency of 300 KHz to three MHz.
memory (RFID)
The amount of data that can be stored on the microchip in an RFID tag.
memory block
Memory on the microchip in an RFID tag is usually divided into sections, which can be read or written to individually.

Some blocks might be locked, so data can't be overwritten, while others are not.

microwave tags
A term that is some time used to refer to RFID tags that operate at 5.8 GHz.

They have very high transfer rates and can be read from as far as 30 feet away, but they use a lot of power and are expensive. Some people refer to any tag that operates above about 415 MHz as a microwave tag.

A condition that exists when the data retrieved by the scanner or reader in the antenna is different from the corresponding data in the tag.
Changing the radio waves traveling between the reader and the transponder in ways that enable the transmission of information.

Waves be changed in a variety of ways that can be picked up by the reader and turned into the ones and zeroes of binary code.

Waves can be made higher or lower (amplitude modulation) or shifted forward (phase modulation).

The frequency can be varied (frequency modulation), or data can be contained in the duration of pulses (pulse-width modulation).

multiple access schemes
Methods of increasing the amount of data that can be transmitted wirelessly within the same frequency spectrum.

Some RFID readers use Time Division Multiple Access, or TDMA, meaning they read tags at different times to avoid interfering with one another.

An electronic device that allows a reader to have more than one antenna.

Each antenna scans the field in a preset order. This reduces the number of readers needed to cover a given area; such as, a dock door, and prevents the antennas from interfering with one another.

A device that supports multiple readers by checking each one in accordance with a scheduling scheme.
nano block
The term "Alien Technology" uses to describe its tiny microchips, which are about the width of three human hairs.
near-field communication
RFID reader antennas emit electromagnetic radiation (radio waves).

If an RFID tag is within full wavelength of the reader, it is said to be in the "near field."

If it is more than the distance of one full wavelength away, it is said to be in the "far field."

The near field signal decays as the cube of distance from the antenna, while the far field signal decays as the square of the distance from the antenna.

So passive RFID systems that rely on near-field communication (typically low- and high-frequency systems) have a shorter read range than those that use far field communication (UHF and microwave systems).

Unwanted ambient electrical signals or electromagnetic energy found in the operating environment of RFID equipment.

Noise can be caused by other RF devices, robots, electric motors and other machines.

nominal range
The read range at which the tag can be read reliably.
null spot
Area in the reader field that doesn't receive radio waves.

This is essentially the reader's blind spot. It is a phenomenon common to UHF systems.

List of Radio Frequency Identification or RFID articles.