NXP Semiconductors
AN11740
PN5180 Antenna design
AN11740
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Application note
COMPANY PUBLIC
Rev. 1.1 — 19 June 2018
345311
24 of 62
(1) Antenna impedance tuned and measured between TX1 and TX2
Fig 20. ITVDD versus antenna impedance
4.2 Antenna for reader mode
If the PN5180 is used in pure reader mode only, i.e. the PN5180 is not used in card
mode or as passive P2P target, the ANT1 and ANT2 pins do not need to be used.
In such case the CAntx are not used, and the corresponding design is done without
considering the PLM (passive load modulation).
In this document the focus is on the asymmetrical antenna tuning. The principle of the
tuning and matching of the symmetrical antenna tuning is very similar, using the same
tuning steps. However, the detailed specifics related to the symmetrical antenna tuning
and especially to the related DTC can be found in [14].
4.2.1 Antenna matching
For the proper antenna design the antenna impedance must be measured using an
impedance analyzer or VNA (vector network analyzer). Such a VNA can be a high-end
tool from Agilent or Rohde & Schwarz (like the R&S ZVL (see
Ref. [7]
), as normally used
in this document), but might be a cheap alternative with less accuracy like e.g. the
miniVNA Pro (see [8]). In any case the analyzer needs to be able to measure the
impedance in magnitude and phase (vector).
Such VNA can be used to measure the antenna coil as well as the antenna impedance
including the matching circuit.
The antenna matching is done with the following steps:
8. Measure the antenna coil
9. Define target impedance and Q-factor
10. Define the EMC filter
