ST ST25R3911B, Руководство пользователя

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Antenna matching UM2042
20/25 DocID029132 Rev 3
3 Antenna matching
The default matching network assembled enables VHBR operation up to 3.4 Mbps.
Components for an optional NFC Forum matching are placed on the board. Exchanging the
components as indicated in
Table 1 will increase the Q factor of the antenna system. VHBR
communication at 3.4 Mbps and 1.7 Mbps bit rate will not be supported anymore, but the
read range for lower data rate applications will increase, up to 20%.
The matching impedance will remain the same when switching between the two matchings.
VHBR matching
The VHBR matching is designed with a target Q-Factor of 8. The matching impedance is
around 12.8 + j5
Ω . The HW based AAT algorithm will typically adjust to an AAT value of 8
(see Figure 13 ).
Figure 13. VHBR matching with an AAT setting of 8
NFC Forum matching
The NFC Forum matching is designed with a target Q-Factor of 16.
To switch to the NFC Forum matching the user needs to change the components listed in
Table 1 .