SEW290 WCDMA Module
20
4.7
Antenna Interface
In
this
module
，
we
have
one
antenna
port
for
signal
transfer.
To
reduce
the
RF
trace
loss,
the
antenna
port
in
the
module
had
better
be
as
close
as
close
as
possible
to
the
antenna
pad
in
the
PCB.
For
maximum
transmitter
power
and
receiver
sensitivity
,
a
50
Ω
transmission
line
is
suggested
to
connect
the
antenna
pad
and
the
antenna
port
of
the
module.
In
addition,
the
RF
signal
will
be
impacted
by
high
data
rate.
We
strongly
suggest
USIM
signal
trace
to
be
short
as
possible
and
as
far
away
as
possible
from
the
RF
trace
and
power
line.
To
prevent
cross
coupling
,
signal
traces
on
your
PCB
must
not
be
routed
through
the
module
backside.
User can connect an antenna with coxial cable to the antenna connector. Please notice the dimension of the
coxial cable should match the module’s connector.
The external antenna must be matched properly to achieve
best performance regarding radiated power, DC-power consumption, modulation accuracy and harmonic
suppression. Antenna matching networks are not included on the SEW290 Module PCB and should be placed
in the host application.
4.7.1
Antenna Design Requirements
The Module's antenna applies to mobile equipment standards, 1
＜
VSWR
＜
2, input impedance is 50 ohm. Under
different environments, the antenna gain requirements are also different, in general, in-band gain is larger, with
external gain is small, the performance of the antenna is better.
Our FCC Grant imposes a maximum gain for the antenna subsystem: 2dBi for the cellular band and 2dBi for the
PCS band.
Warning:
Excessive gain could damage sensitive RF circuits and void the warranty.
4.7.2
Interference
Besides the antenna performance, the interference on the user board also affects the radio performance
(especially the TIS) of the module. To guarantee high performance of the module, the interference sources on the
user board must be properly controlled.
On the user board, there are various interference sources, such as the LCD, CPU, audio circuits, and power
supply. All the interference sources emit interference signals that affect the normal operation of the module. For
example, the module sensitivity can be decreased due to interference signals. Therefore, during the design, you
need to consider how to reduce the effects of interference sources on the module. You can take the following
measures: Use an LCD with optimized performance; shield the LCD interference signals; shield the signal cable
of the board; or design filter circuits.
4.8
LED Status Indicator
SEW290 provides a SIG_LED pin as LED status indicator. The interface can be configured as a programmable
current source, to drive the external indicator LED. Tune the resistance of R to tune LED's brightness.
