UC-00-M33 EN R1.0 Hardware Design 15
3.2 Antenna Feed Design
UM981 just supports feeding the antenna from the outside of the module rather than
from the inside. It is recommended to use devices with high power and that can
withstand high voltage. Gas discharge tube, varistor, TVS tube and other high-power
protective devices may also be used in the power supply circuit to further protect the
module from lightning strike and surge.
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 UM981 External Antenna Feed Reference Circuit
Notes:
1. L1: feed inductor, 68 nH RF inductor in 0603 package is recommended
2. C1: decoupling capacitor, recommended to connect two capacitors of
100 nF/100 pF in parallel
3. C2: DC blocking capacitor, recommended 100 pF capacitor
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