AN3255 datasheet(13/24 Pages) STMICROELECTRONICS

13 / 24 page

AN3255

Application description

Doc ID 17784 Rev 1

13/24

The efficiency of data transfers between the RFID reader and tag depends on the tuning of

their respective antenna. This is done by adjusting the following components:

●

CS is the serial capacitance used to adapt the impedance of the reader antenna RLC

equivalent circuit:

CS = C8 + C8’

●

CP is the parallel capacitance used to tune the resonant frequency of the reader RLC

equivalent circuit:

CP = C7 + C7’

●

RS is the serial resistor used to fine tune the quality factor of the reader RLC resonant

equivalent circuit:

RS = R8

Refer to application note AN1806 for details on how to design a reader antenna and infer the

values of CP, CS and RS. This document is associated with a software tool using the Grover

method to calculate the inductance of rectangular planar antennas.

Warning:

The values of CS, CP, and RS are dependant. Tuning one of

them impacts the 2 others. The best compromise must be

found to achieve a good tuning for the reader antenna (refer

to AN1806).

AN3255 数据表(PDF) 13 Page - STMicroelectronics