Nordic 3 - Matching Network; Antenna; Nfc

6 Hardware description: Smart Remote 3 nRF52 product example
Doc. ID 4374_139 v1.1
Page 52
C15
10
µ
F
C13
10nF
MIC_CLK
MIC_DOUT
R13
100R
C29
15pF
C28
15pF
MIC_DOUT
MIC_CLK
C22
10
µ
F
C21
10nF
R7
100R
C24
15pF
C23
15pF
FB1
600R/0.5A
FB2
600R/0.5A
VIO_PDM
SB9
SB11
SB10
VDD
3
LR
2
CLK
1
DOUT
4
GND
5
U3
MP34DB02
VDD
3
LR
2
CLK
1
DOUT
4
GND
5
U2
MP34DB02
Figure 40: Digital microphones schematic
6.3.8 Matching network
The matching network is made up of discrete components and the impedance is tuned to 50 Ω.
6.3.9 Antenna
The antenna is of meander type, and is integrated in the PCB layout.
The antenna is tuned to be resonant at 2.44 GHz, and the impedance is matching the 50 Ω output from the
matching network. The antenna in this design is tuned for this layout only, and with the same plastic casing.
If the layout and/or the casing is changed, it is likely the antenna must be re-tuned. The antenna can be re-
tuned by adjusting the values of C14, R17, and L4. The exact values of the components must be determined
by measurements with a vector network analyzer.
X1
32MHz
C1
12pF
C2
12pF
C7
100pF
XC1
XC2
P0.22
P0.23
P0.24
SWDCLK
SWDIO
RF
C3
0.8pF
C8
100nF
L1
3.9nH
VSS
31
ANT
30
DEC2
32
DEC3
33
XC1
34
XC2
35
VDD
36
SWDCLK
25
SWDIO
26
P0.22
27
P0.23
28
P0.24
29
U1
nRF52832-QFAA
VDD
DEC3
DEC2
C6
N.C.
24
2322
IR_REC
IR_LED
ICM-20608_INT
C14
1.0pF
ANT
Antenna
R17
0R
L4
1.8nH
Figure 41: Matching network and antenna circuit
6.3.10 NFC
NFC connector circuitry.