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Figure 49: 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 RF_ANT as possible;
z
Antenna matching circuit should be closed to the antenna;
z
Keep the RF traces as 50
Ω
;
z
The RF traces should be kept far away from the high frequency signals and strong disturbing source.
4.19.3.
FM Antenna Interface
The module provides 2 FM antenna pad named FM_ANT_P and FM_ANT_N, these are difference signal. The
FM antenna interface circuit is recommended as following:
Figure 50: FM antenna matching circuit
Normally, R301\R302\R303\R304 are 0
Ω
, C301\C302\C303\C304 are not mounted.
The earphone is often used for FM antenna, as an example, the pin GND of the 3.5mm earphone is connected to
the FM interface. The circuit is recommended as following:
Figure 51: GND pin of the earphone use to be the FM antenna interface
Normally, R301\R303 are 0
Ω
, C301\C302\C303\C304\L301 are not mounted.
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Содержание SIM800H
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