Mandatory Components; Rf Line To Antenna Matching - Silicon Laboratories Z-WAVE 700 Integration Manual

Instruction: Z-Wave Z-Wave 700 Integration Guide
Figure 8.1: Recommended RF matching component for the EFR32ZG14 gateway SoC: Murata LFD21868MMF5E233 IPD

8.1.1 MANDATORY COMPONENTS

Manufacturer
Murata
8.2

RF LINE TO ANTENNA MATCHING

Finding appropriate values for the components should be considered an iterative task. It is recommended to add a pi network for
matching as shown in Figure 8.2. The following matching strategy is proposed:
1. Calibrate your Vector Network Analyzer (VNA) for a frequency range larger than the intended bandwidth of the antenna.
2. Connect an RF coaxial cable to the RF line (for instance by soldering a pigtail to the line). Connect the RF coaxial cable to
a VNA to measure the reflection coefficient, S11, looking into the antenna through the matching network.
a. Be sure to have a good connection to the ground plane to get the best electrical performance and the highest
mechanical robustness during the measurement.
b. Make sure to route the pigtail towards the center of the PCB and then perpendicularly away from the PCB at the
center point. This will limit the effect of the cable on the measured data as much as possible.
3. Start out with no components on the antenna network shown in Figure 8.2:
a. The shunt components are not mounted.
b. The series component is not mounted.
4. Use line extension on the VNA to move the reference point to the footprint of R1 and R2.
a. This is achieved when the locus of the S-parameters in the Smith chart on the VNA have assembled in a point at
the right edge of the Smith chart.
5. Mount a 0 Ω resistor at R2 in Figure 8.2
6. Measure reflection coefficient for the frequency of interest (the frequency half way between the lowest frequency and
the highest frequency of the region of interest).
7. Use an online matching tool to calculate series and shunt component values to achieve 50 Ω match on the coaxial line.
8
U1B
EFR32ZG14
RF Crystal RF I/O
6
HFXTAL_N SUBGRF_OP
SUBGRF_IP
7
HFXTAL_P
RF Analog Power
SUBGRF_IN
5
RFVDD
SUBGRF_ON
Ground
13
RFVSS
EFR32ZG14
Applicable
L103
VDCDC
C107
C106
BLM03AX241SN1D
220N 56P
GND
U2
LFD21868MMF5E233
10
VDD
9 9
TXP
11 7
RXP
2
50R_RF_OUT
ANT
1
GND1
12 6 3
RXN GND2
4
GND3
10 8 5
TXN GND4
GND
Sub-GHz
matching
network
Table 8.1: IPD
Component Number
LFD21868MMF5E233
EOL issued
ZGM130S
Applicable
INS14487-3 | 2/2019