your position is our focus
2.7 Active vs. Passive Antenna
ceiver
cannot
provide
e
Time-To-First-Fix
(TTFF).
Therefore, good sky visibility is very important.
ge
Carrier-To-Noise-Ratio
(C/No)
of
the
average
of
the
C/No
ratio
of
as.
First
some
general
issues:
•
A
GPS
receiver
needs
to
receive
signals
from
as
many
satellites
as
possible.
A
GPS
re
optimal
performance
in
narrow
streets
between
high
buildings
(i.e.
in
urban
canyons),
in
underground
parking
lots
or
if
objects
cover
the
ant nna.
Poor
sky
visibility
may
result
in
position
drift
or
a
prolonged
•
A
GPS
receiver
will
only
achieve
the
specified
performance
if
the
avera
the
strongest
satellites
reaches
at
least
44
dBHz.
In
a
well-designed
system,
high
elevation
satellites
should
be
in
the
range
between
44
dBHz
and
about
50
dBHz.
With
a
standard
off-
the-shelf
active
antenna,
47
dBHz
should
easily
be
achieved.
Even the best receiver can’t make up for
signal loss due to a poor antenna, in-band jamming or a bad RF-board design.
Table
4
looks
at
some
of
the
issues
to
consider
when
selecting
active
or
passive
antenn
Active Antenna
Passive Antenna
Active
antenna
connected
to
the
GPS
module.
Passive
patch
antennas,
chip
antennas
or
helical
antennas
connected
with
a
micro
strip
or
strip
line
to
the
GPS
module.
A
wide
range
of
active
patch
or
helical
antennas
are
available
on
the
market.
They
differ
in
size,
sensitivity
and
power
consumption
•
Passive
patch
antennas
or
helical
antennas
are
available
in
different
form
factors
and
sensitivities
•
Needs
more
power
than
a
passive
antenna
•
Antenna
must
be
connected
with
a
care
designed
micro
strip
or
strip
line
to
the
GP
fully
S
e
antenna
must
e
sensitivity
of
the
GPS
antenna
to
ting
circuits
or
general
signal
jamming.
module
to
ensure
a
good
GPS
performance.
•
The
PCB
design
with
a
passiv
consider
th
other
radia
•
Due
to
the
proximity
of
antenna,
GPS
and
other
circuits,
in-band
jamming
may
become
electronic
a
critical
issue.
Table 4: Active vs. Passive Antenna
you
are
not
an
expert
in
RF
designs
and
place
the
antenna
away
from
Note
Take
an
active
antenna,
if
noise
emitting
circuits.
GPS
Modules
-
System
Integration
Manual
(SIM)
(incl.
Reference
Design)
System
Consideration
GPS.G4-MS4-05007-A1
Page 42
