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NXP Semiconductors
UM10883
PN7462 family Quick Start Guide - Development Kit
UM10883
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© NXP B.V. 2018. All rights reserved.
User manual
COMPANY PUBLIC
Rev. 1.6 — 14 May 2018
319816
11 of 120
2.2.6 Antenna coil and related matching circuit
In general, there are two antenna tunings possible with PNEV7462B board:
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asymmetrical
-
symmetrical
The asymmetrical tuning is the standard tuning as taken from the existing NXP NFC
frontend design recommendations. It uses EMC cut off frequencies >17MHz, which
results in an asymmetrical transfer function, but shows a good detuning and loading
behavior. The asymmetrical transfer function has some disadvantages regarding the
pulse shapes and receiver performance, and requires a slightly reduced Q factor of the
antenna coil circuit itself.
Symmetrical coupling is used with DPC (Dynamic Power Control) feature of the PN7462
and offers an improved overall RF performance. This requires the antenna to be
“symmetrically” tuned and it requires the AGC to correlate with the driver current ITVDD.
and it requires the dynamic power control to be properly calibrated. The DPC Antenna
tuning (“symmetrical tuning with DPC) combines the advantages of enough field strength
at 4cm with the automatic power control to limit the maximum field strength at a close
distance. This tuning assures passing related EMVCo tests.
2.2.6.1 Default board antenna
Default 65x65 mm board antenna is designed to use symmetrical tuning (see Fig 9). This
antenna is not an optimal antenna as such, but intends to demonstrate the performance
and register settings of the PN7462 under typical design constraints like LCD or another
metallic object (e.g. PCB) inside the antenna area. Inside of the antenna area is filed of
10x10 fields simulating metallic object in real application.