NXP Semiconductors
AN145715
PN544 Antenna Design Guide
145715
© NXP B.V. 2006. All rights reserved.
Application Note
Rev. 1.5 — 28th August 2009
36 of 43
The series equivalent resistance of the antenna at the operating frequency f
op
=
13.56MHz can be calculated out of the characteristic circuit.
Fig. 31 Series equivalent resistance calculation
(
)
)
56
.
13
(
2
56
.
13
)
(
)
56
.
13
(
2
MHz
R
L
f
R
R
fres
fres
R
MHz
R
p
a
op
s
a
p
p
⋅
⋅
⋅
+
=
=
π
The parallel equivalent circuit always has to be calculated by means of the series
equivalent circuit using equation
88H88H
(19).
The parallel resistance R
p
(fres) obtained by measurements has to be calculated to the
parallel equivalent value at 13.56MHz. This is accomplished in equation
89H89H84H
(21).
R
a
in equation
90H90H85H
(22) is then calculated by using R
p
(13.56Mhz).
8.3
22B22B
PULSE shape check
The following pulse shape checks are a quick way for investigating the shaping of
the generated RF-field. Chapter
91H91H86H
8.5 points out the pulse shape timings according
to ISO/IEC18092:2004. Please note that always to the latest version of
ISO/IEC18902 is referenced.
The correct measurement techniques needs to be carried out in ISO/IEC 22536
(NFCIP – RF Interface Test methods) and/or ISO/IEC 10373-6 (Identification cards –
Test methods) and ISO/IEC14443!
The Q-factor can be checked by using the fact that the Q-factor has a direct influence on
the edges of the modulation shape.
An oscilloscope with a bandwidth of at least 50MHz has to be used to carry out the
module shape measurements (
92H92H87H
Fig 39).
R
a
L
a
C
a
R
s
L
a
C
a
R
p
