January 2009

Rev 1

1/24

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

Figure 2.

An antenna designed for a specific chip and frequency

ai15802

Tag

Reader

ai15802

Antenna

Chip

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