Radio Frequency Identification (RFID): Definitions

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.

The read range at which the tag can be read reliably.

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.

An Auto-ID Center-designed system for looking up unique Electronic Product Codes and pointing computers to information about the item associated with the code.

ONS is similar to the Domain Name Service, which points computers to sites on the internet.

Capability of a tag to operate in any orientation.

Also called a field-programmable tag.

An RFID tag that can be written to once and read many times (see WORM).

1. The position of a tag antenna vis-a-vis a reader antenna. 2. Alignment of the tag with respect to the reader or tag.

1. An RFID tag without a battery. 2. A tag that contains no internal power source.

A small square reader antenna made from a solid piece of metal or foil.

The ability of a particular radio frequency to pass through non-metallic materials.

Low-frequency systems have better penetration than UHF systems.

Also called a phantom transaction or false read.

When a reader reports the presence of a tag that doesn't exist.

An Auto-ID Center-designed method of describing products in a way computers can understand.

PML is based on the widely accepted eXtensible Markup Language used to share data over the internet in a format all computers can use.

The idea is to create a computer language that companies can use to describe products so that computer can search for, say, all "softdrinks" in inventory.

A server that responds to requests for Physical Markup Language (PML) files related to individual Electronic Product Codes.

The PML files and servers will be maintained by the manufacturer of the item. The name PML server has been replaced by EPC Information Service.

The amount of RF energy radiated from a reader or an active tag.

The higher the power output, the longer the read range, but most governments regulate power levels to avoid interference with other devices.