AN2866 Datasheet, PDF (1/24 Pages) STMicroelectronics – RFID tags extract all of their power

AN2866
Application note
How to design a 13.56 MHz
customized tag antenna
Introduction
RFID (radio-frequency identification) tags extract all of their power from the reader’s field.
The tags’ and reader’s antennas form a system of coupled inductances as shown in
Figure 1. The loop antenna of the tag acts as a transformer’s secondary.
The efficient transfer of energy from the reader to the tag depends on the precision of the
parallel resonant RLC loop antennas tuned to the carrier frequency (usually 13.56 MHz).
The purpose of this application note is to give a step-by-step procedure to easily design a
customized tag antenna.
Figure 1. RFID tag coupled to a reader’s magnetic field
Tag
Reader
Figure 2. An antenna designed for a specific chip and frequency
ai15802
Chip
Antenna
ai15802
January 2009
Rev 1
1/24
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