Antenna Interface - SimCom SIM900D Hardware Design

4.15 Antenna Interface

SIM900D provides a RF antenna interface. The customer's antenna should be located in the customer's main
board and connect to module's antenna pad through microstrip line or other type RF trace which impendence must
be controlled in 50Ω. To facilitate the antenna tuning and certification test, a RF connector and an antenna
matching circuit should be added. The following figure is the recommended circuit.
MODULE
In this figure, the components R101,R102,C101 and C102 is used for antenna matching, the components' value
only can be got after the antenna tuning. Usually, matching components' value is provided by antenna vendor, the
default value of R101 and R102 are 0Ω, and reserve the place of C101 and C102 without soldering.
The RF test connector in above figure is used for conducted RF performance test, and should be placed as close as
possible to the module's RF_ANT pin. The traces in bold type should be treated as 50Ω impedance controlled line
in PCB layout. For details about radio frequency trace layout, please refer to document [8].
SIM900D_Hardware Design_V2.02
RF test connector
GND
59
RF_ANT
60
GND 61
Figure 37: Antenna matching circuit
Matching circuit
R101
J102
C101 C102
40
Smart Machine Smart Decision
Antenna feed pad
J101
R102
2012-05-07