12
Hardware Design
UC-00-M48 EN R1.1
3.2
Antenna Feed Design
UM960L just supports feeding the antennal from the outside of the module rather than
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.
UM960L
ANT_IN
ANT
VCC_RF
GND
C2
ANT_BIAS
L1
C1
D1
D2
Figure 3-2 UM960L External Antenna Feed Reference Circuit
Remarks:
L1: feed inductor, 68nH RF inductor in 0603 package is recommended.
C1: decoupling capacitor, it is recommended to connect two capacitors of
100nF/100pF in parallel.
C2: DC blocking capacitor, recommended 100pF capacitor.
Not recommended to take VCC_RF as ANT_BIAS to feed the antenna (VCC_RF is not
optimized for the anti-lightning strike and anti-surge due to the compact size of the
module).
D1: ESD diode, choose the ESD protection device that supports high frequency
signals (above 2000 MHz).
