ITPEC FE Morning April 2018 Question 72

The reader/writer's electromagnetic field powers the tags in range so they can send their data — how an RFID system communicates.

An RFID tag holds an IC chip and an antenna. A passive tag has no battery: the radio field generated by the reader/writer induces enough power in the antenna to run the chip, which then sends its ID and data back by radio. The reading is contactless, works through packaging, and can cover several tags at once. (Active tags carry their own battery for longer range, but the reader-to-tag model is the same.)

Answer (b)

Why not others:

• •(a) — tags only answer a reader; they do not talk to each other or form a mesh network, which describes sensor networks such as ZigBee
• •(c) — computing longitude and latitude from several satellites is GPS; an RF tag has no positioning function
• •(d) — RFID is wireless by definition, so there is no wired connection, and the radio link relies on error checking such as a CRC to stay reliable

Key rule: RFID is contactless reading by a reader/writer whose field powers passive tags; it has no tag-to-tag networking and no positioning.

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