Smart Machine Smart Decision
Figure 50: GSM simple antenna matching circuit
Normally R101 is 0Ω, C101 and C102 are not mounted.
4.19.2. Bluetooth Antenna Interface (Only SIM800H)
The SIM800H module provides a Bluetooth antenna pad named BT_ANT.
The external antenna must be matched properly to achieve best
performance, so the matching circuit is necessary,
the connection is recommended as in the following figure:
Figure 51: Bluetooth antenna matching circuit
R201, C201, C202 are the matching circuit, the value should be defined by the antenna design. Normally R201 is
1.2nH, C202 is 1.5pF and C201 are not mounted.
There are some suggestions for placing components and RF trace lying for GSM and Bluetooth RF traces:
z The RF connector is used for conducted test, so keep it as close to pin GSM_ANT as possible;
z Antenna matching circuit should be closed to the antenna;
z Keep the RF traces as 50Ω;
z The RF traces should be kept far away from the high frequency signals and strong disturbing source.
4.19.3. FM Antenna Interface
SIM800H&SIM800L_Hardware Design_V2.02 53
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The module provides 2 FM antenna pad named FM_ANTP and FM_ANTN, these are difference signal. The FM
antenna interface circuit is recommended as following:
