WA_DEV_W228_PTS_002 Rev
001
Page 86 of 108
Product Technical Specification &
Customer Design Guidelines
RF Interface
The
RF
interface
allows
the
transmission
of
radio
frequency
(RF)
signals
from
the
WISMO228
to
an
external
antenna.
This
interface
has
a
nominal
impedance
of
50
Ω
and
a
DC
resistance
of
0
Ω
.
RF Connection
The
RF
input/output
of
the
WISMO228
is
through
one
of
the
castellation
pins
(Pin
21,
ANT),
with
grounded
castellation
pins
at
both
sides.
This
castellation
pin
must
be
connected
to
a
50
Ω
RF
line
in
order
to
protect
the
antenna
line
from
the
noise
coming
from
baseband
signals.
Figure 45. Example of a 50
Ω
RF Line
The
50
Ω
RF
line
is
surrounded
by
two
ground
planes
in
order
to
protect
the
antenna
line
from
noise.
The
length
of
the
line
shouldn’t
be
too
long
(no
more
than
a
few
centimeters)
because
of
RF
insertion
loss.
The
width
of
the
line
must
be
calculated
in
order
to
ensure
a
50
Ω
characteristic
impedance.
For
this
same
reason,
the
embedded
RF
line
should
likewise
be
kept
about
1cm
away
from
any
(noisy)
baseband
signal
in
order
to
ensure
a
good
RX
sensitivity
level.
The
other
end
of
the
50
Ω
RF
line
can
be
connected
to
an
RF
connector
or
to
a
soldering
pad
in
order
to
connect
an
antenna.
It
is
also
possible
to
use
an
antenna
chip
or
to
design
a
PCB
antenna
directly
on
the
application
board.
The
ANT
pin
of
the
WISMO228
is
ESD
protected
for
both
±
4KV
contact
and
±
8KV
air
discharge.
Note:
The correct antenna cable and connector should be chosen in order to minimize loss in the frequency
bands used for GSM800, EGSM900, DCS1800 and PCS1900.
Castellation pin
for ANT
50
Ω
RF line
Содержание WISMO228
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