your position is our focus
4.3.3 Active Antenna Bias Power
ion
ption of LEA-4M. For LEA-4M and NEO-4S
nsider
the
This sect
only applies to TIM-4x and LEA-4x receivers with the exce
refer to Section 4.3.3.1.
There
are
two
ways
to
supply
the
bias
voltage
to
pin
V_ANT
.
It
can
be
supplied
externally
(please
co
datasheet
specification)
or
internally.
For
Internal
supply,
the
VCC_RF
output
must
be
connected
to
V_ANT
to
supply
the
antenna
with
a
filtered
supply
voltage.
However,
the
voltage
specification
of
the
antenna
has
to
match
the
actual
supply
voltage
of
the
ANTARIS
®
4
GPS
Receiver
(e.g.
3.0
V).
Active Antenna
Active Antenna
ANTARIS GPS Module
GND
RF_IN
GND
ANTARIS GPS Module
GND
RF_IN
GND
V_ANT
VCC_RF
LNA
external
supply
antenna
voltage
V_ANT
VCC_RF
LNA
R_BIAS
R_BIAS
Figure 61: Supplying Antenna bias voltage
Since
the
bias
voltage
is
fed
into
the
most
sensitive
part
of
the
receiver,
i.e.
the
RF
input,
this
supply
should
be
virtually
free
of
noise.
Usually,
low
frequency
noise
is
less
critical
than
digital
noise
with
spurious
frequencies
with
harmonics
up
to
the
GPS
band
of
1.575
GHz.
Therefore,
it
is
not
recommended
to
use
digital
supply
nets
to
feed
pin
V_ANT
.
An
internal
switch
(under
control
of
the
ANTARIS
®
4
GPS
software)
can
shutdown
the
supply
to
the
external
antenna
whenever
it
is
not
needed.
This
feature
helps
to
reduce
power
consumption
when
the
GPS
receiver
is
in
Sleep
Mode.
4.3.3.1
Antenna Bias Voltage for LEA-4M and NEO-4S
his section only applies to LEA-4M and NEO-4S For all other receivers, refer to Section 4.3.3.
EO-4S
and
LEA-4M
do
not
provide
the
antenna
bias
voltage
for
active
antennas
on
the
RF_IN
pin.
It
is
therefore
essary
to
provide
this
voltage
outside
the
module
via
an
inductor
as
indicated
in
Figure 62
.
u-blox
S-36NX).
Alternative
parts
are
feasible
if
the
inductor’s
resonant
frequency
matches
the
GPS
frequency
of
1575.4MHz.
T
N
nec
recommends
using
an
inductor
from
Coilcraft
(0402C
Low Noise Amplifier
Active Antenna
RF_IN
VCC_RF
GND
GND
Figure 62: Recommended wiring for active antennas
Passive
antennas
can
directly
be
connected
to
the
RF_IN
pin
of
LEA-4M
and
NEO-4S.
No
inductor
is
required
in
this
case.
Note
Please
refer
to
section
3.6.6
for
layout
recommendations
for
the
antenna
bias
voltage
inductor.
GPS
Modules
-
System
Integration
Manual
(SIM)
(incl.
Reference
Design)
Receiver
Description
GPS.G4-MS4-05007-A1
Page 74
