Shanghai SIMCom Wireless Solutions Limited 8PSA301 Benutzerhandbuch
Smart Machine Smart Decision
25
1uF
VBAT
VIB_DRV
Module
Vibrator
0R
Figure 25: Vibrator reference circuit
Antenna Interface
SIM8905A provides two antenna interfaces including MAIN antenna and DRX antenna. To ensure good RF
performance, users should meet the following requirements:
●
Keep the RF traces at 50
Ω.
●
Maintain a complete and continuous reference ground plane from antenna pin to the RF connector.
●
The RF traces should be away from any other noisy traces.
●
Keep the RF traces as short as possible.
MAIN Antenna reference circuit
The recommended circuit is shown as below:
RF connector
(optional)
C1
Module
87
ANT_MAIN
GND
C2
88
R1
Matching circuit
MAIN ANT
86
GND
Figure 26: MAIN antenna recommended circuit
R1, C1 and C2 are antenna matching components in Figure 27, the value of these components are determined
according to the antenna tuning results. By default, R1 is 0
Ω, C1 and C2 are reserved. The RF connector in Figure
27 is used to ensure the accuracy and convenience of the conduction testing, so SIMCOM suggest keeping it. If
considering Low-Cost BOM, user can cancel the connector.