Neo_M680 GPRS Module Hardware User Guide
Copyright © Neoway Technology Co., Ltd
27
Figure 3-28
Reference design for antenna interface
On two
-
layer boards which cannot control resistance properly, the RF route should be as short and smooth
as possible and at a width of 0.5 mm; the RF is 0.5 mm away from the ground.
Figure 3-29 shows a two-layer board application. The RF is connected to GSC RF connector through traces
on PCB, which is connected to the antenna via cable.
Figure 3-29
RF layout reference
ESD protection is built in module. For special ESD protection, an ESD diode can be placed close to the
antenna. But ensure using a low junction capacitance ESD diode. The junction capacitance should be less
than 0.5 pF, otherwise the RF signal will be attenuated. RCLAMP0521P from Semtech, or ESD5V3U1U
from Infineon, can be used here.
On the PCB, keep the RF signals and RF components away from high-speed circuits, power supplies,
transformers, great inductors, the clock circuit of single-chip host, etc.
GPRS
Module
ANT
C1
GPRS_ANT
L2
L1
The RF traces are wide 0.5
mm; leave space at least 0.5
mm between the coppers.
Drill enough grounding holes.
Ensure that the ground pins on both
sides of the antenna are grounded
completely and they form a complete
circle with grounding copper.
