Rainbow Electronics AT88RF1354 - Manual (Page 14)

14
13.56 MHz Type B RF Reader
8547A −RFID−10/08
7. Typical Application
7.1. Operating Principle
Contactless RF smart cards operating at 13.56 Mhz are powered by and communicate with the reader via inductive
coupling of the reader antenna to the card antenna. The two loop antennas effectively form a transformer.
An alternating magnetic field is produced by sinusoidal current flowing thru the reader antenna loop. When the card
enters the alternating magnetic field, an alternating current (AC) is induced in the card loop antenna. The PICC
integrated circuit contains a rectifier and power regulator to convert the AC to direct current (DC) to power the
integrated circuit.
The reader amplitude modulates the RF field to send information to the card. The PICC contains a demodulator to
convert the amplitude modulation to digital signals. The data from the reader is clocked in, decoded and processed
by the integrated circuit.
The card communicates with the reader by modulating the load on the card antenna, which also modulates the load
on reader antenna. ISO/IEC 14443 PICCs use a 847.5 khz subcarrier for load modulation, which allows the reader to
filter the subcarrier frequency off of the reader antenna and decode the data.
Figure 3. The card antenna and reader antenna effectively form a transformer
IC
READER