What are the components of an RFID system and of an individual RFID tag, and how is a passive tag powered?

A system has a reader, an antenna, and a passive tag; a tag itself is chip + antenna + packaging. A passive tag draws power contactlessly from the reader's field via electromagnetic induction.

A typical RFID system has three parts: the reader, the antenna, and the passive tag. Energy is transferred contactlessly via electromagnetic induction — the passive tag has no battery and is energised by the reader's field.

An individual RFID tag has three tightly-coupled elements:

• Chip: stores the information about the physical object; has small memory and a logic unit to process commands.
• Antenna: transmits the data to a reader via radio waves; antenna size largely determines the tag's range.
• Packaging: encases chip and antenna so the label can be attached to objects and protected from the environment.

Tags vary enormously in size and form — from coin-sized chips to thin, flexible labels.

Tip: "Passive" = no battery; the tag literally harvests the energy to power its chip from the reader's electromagnetic field. That's why read range is short and antenna size matters so much.