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If the antenna feed supply ANT_BIAS and the module’s main supply VCC use the
same power rail, the ESD, surge and overvoltage from the antenna will have an
effect on VCC, which may cause damage to the module. Therefore, it is
recommended to design an independent power rail for the ANT_BIAS to reduce the
possibility of module damage.
Figure 3-2 UM980 External Antenna Feed Reference Circuit
Notes:
L1: feed inductor, 68 nH RF inductor in 0603 package is recommended
C1: decoupling capacitor, recommended to connect two capacitors of
100 nF/100 pF in parallel
C2: DC blocking capacitor, recommended 100 pF capacitor
It is not recommended to take VCC_RF as ANT_BIAS to feed the antenna (VCC_RF is
not optimized for anti-lightning strike, anti-surge and over current protection due to
the compact size of the module)
D1: ESD diode, choose the ESD protection device that supports high frequency
signals (above 2000 MHz)
D2: TVS diode, choose the TVS diode with appropriate clamping specification
according to the requirement of feed voltage and antenna withstand voltage
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