Radio; Rf Section; Description Of The Rf Matching; Rf Section Power Supply - Silicon Laboratories BG22 Explorer Kit User Manual

5. Radio

5.1 RF Section

This section gives a short introduction to the RF section of the BRD4108A board.
The schematic of the RF section is shown in the figure below.
Supply
Filtering
VDCDC
R4
0R
C11
100N
NM
GND
R5
0R
C18
100N
NM
GND

5.1.1 Description of the RF Matching

The impedance of the RF port of the EFR32BG22 is matched to 50 Ohm. The RF2G4_IO pin is connected to a four-element impedance
matching and harmonic filter circuitry, and a DC blocking capacitor.
Note: Due to the thicker PCB stack-up, the radiated level of the 5th harmonic has been increased. Therefore, compared to the 3-ele-
ment L-C-L matching networks presented in the
plied on the BRD4108A board has an additional small value capacitor in the C3 position, and small modification of the C4 capcitor was
also required. With these changes, the suppression of the radiated 5th harmonic was improved, and so its level is under the relevant
regulation limit.
The on-board ceramic antenna is also matched to 50 Ohm by its impedance matching components and connected to the EFR32BG22.

5.1.2 RF Section Power Supply

On the BRD4108A, the supply for the radio (RFVDD) and the power amplifier (PAVDD) is connected to the on-chip DC-DC converter.
By default, the DC-DC converter provides 1.8 V for the entire RF section (for details, see the BRD4108A schematic).
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High
Frequency
Crystal
U1B
EFR32BG22
RF Cr ys t a l RF I / O
9
HFXTAL_I RF2G4_IO
2 X1
4
38.4 MHz
10
HFXTAL_O
GND
RF Ana l og Powe r Gr ound
12
RFVDD
C12
PA Powe r
120P 15
PAVDD
GND
C19
120P
GND
Figure 5.1. Schematic of the RF Section
AN930.2: EFR32 Series 2 2.4 GHz Matching Guide
2.4 GHz
Matching
Network
L1 L2
CC1
2N7 3N0
14
18P
C3 C4 C5
0P1 1P2
NM
13
RFVSS
GND
UG509: BG22 Explorer Kit User's Guide
Chip Antenna and
Antenna Matching Network
Z7 ANT1
1 2
IN GND
4 3
1P6 GND GND
2450AT18D0100
Z8
Z9
16N
NM
application note, the matching ap-
Radio
Rev. 1.1 | 15