NXP Semiconductors
AN11740
PN5180 Antenna design
AN11740
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Application note
COMPANY PUBLIC
Rev. 1.1 — 19 June 2018
345311
52 of 62
Note:
The HPCF should typically be set to 0 for higher bit rates. For the standard bit
rates (106 kbit/s) the HPCF of 2 or even 3 might improve the performance,
especially under noisy environmental conditions.
MinLevel can be seen as a threshold value for the subcarrier signal on I and Q channel.
The sub carrier signal must exceed the threshold to be taken into account by the PN5180
decoder.
Note:
The MinLevel is dynamically adapted inside the PN5180, i.e. with a very high
level of subcarrier signal the Minlevel is automatically increased internally to
increase the signal to noise ratio.
Min_Level_P can be seen as a threshold for the decoded BPSK signal (BPSK_SUM).
The BPSK signal must exceed the Min_Level_P to be taken into account be the PN5180
data decoder.
Note:
The Min_Level_P setting is not relevant for type A at 106kbit/s at all, but only for
BPSK.
Note:
The unfiltered I and Q channel signals are always present, while the filtered I and
Q signals only apply, when the Rx is active (RxActive).
4.6.3 Noise check
The Fig 47a shows a Q channel signal and the card response LMA (at the
ReferencePICC input) using a type B setting without card response and without noise.
The Fig 47b shows the same test case with the same settings, but in this case some
external noise is coupled into the circuit.
The example as shown in Fig 47b and Fig 48b uses a LCD, which is placed very closely
to the antenna coil. The LCD driver generates current peaks, which couple magnetically
into the antenna coil.
a. No card response, no noise
b. No card response, external noise
Fig 47. Type B without Card response
