NXP Semiconductors PN544, Руководство по конструкции

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NXP Semiconductors
AN145715
PN544 Antenna Design Guide
145715 © NXP B.V. 2006. All rights reserved.
Application Note Rev. 1.5 — 28th August 2009 35 of 43
connection points) before each measurement. Please refer to device manual on how to
carry out these steps.
Settings: S11
Chart: Smith Z
Start frequency: 1 MHz
Stop frequency: above self-resonance frequency of the antenna
8.2.3
46B46B
Series equivalent circuit
The following characteristic circuit elements can be determined by measurements at
characteristic points (see also
86H86H
Fig 35 for series equivalent circuit).
R
s
Equivalent resistance at f = 1MHz
L
a
Equivalent inductance at f = 1MHz
R
p
Equivalent resistance at the self-resonance frequency
f
ra
Self-resonance frequency of the antenna
The antenna capacitance C
a
can be calculated with:
( )
a ra
a
L f
C
2
2
1
⋅ ⋅
=
π
The following
87H87H83H
Fig 37 shows simulation results to determine the characteristic circuit.
a. R
s
= 0.82Ohm, L
a
= 2.99 µH b. R
p
= 18kOhm, f
ra
= 29.14MHz
Fig. 30 Simulation results for characteristic circuit