SimCom SIM900 Reference Design Manual page 15

SIM900 Reference Design Guide Notes
9) RF trace between SMT module RF pad with the RF test connector, RF trace between RF
test connector with the antenna matching circuit, RF trace between the antenna matching
circuit with the antenna feed PAD all should be controlled to 50 Ohm
10) All layers under the antenna feed pad should be copper keep out.
11) Do not layout RF trace in orthogonal
12) When layout surface Microstrip Transmission Line or offset Stripline Transmission
Line , 3W rule should be followed, that means the distance between reference GND with
RF trace should three times more than the width of RF trace.
SIM900_AN_Reference Design Guide_V1.01
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01.27.2010