TIM-5H
-
Hardware
Integration
Manual
Appendix
GPS.G5-MS5-07015-A-1
u-blox
proprietary
Page 42
your position is our focus
B Antennas
Even
the
best
receiver
cannot
bring
back
what
has
been
lost
at
the
antenna.
The
importance
of
the
attention
paid
to
this
part
of
a
GPS/GALILEO
system
cannot
be
stated
highly
enough.
B.1 Selecting the right Antenna
Several
different
antenna
designs
are
available
on
the
GPS/GALILEO
applications
market.
The
GPS/GALILEO
L1
signal
is
right-hand
circular
polarized
(RHCP).
This
results
in
a
style
of
antenna
that
is
different
from
the
well-
known
whip
antennas
used
for
linear
polarized
signals.
The
foremost
antennas
for
GPS/GALILEO
application
designs
are
the
patch
antennas
as
shown
in
Figure 25: Patch Antennas, EMTAC Technology Corp.
Another
style
is
the
quadrifilar
helix
antenna
shown
in
The
actual
geometric
size
of
both
antenna
designs
depends
on
the
dielectric
that
fills
the
space
between
the
active
parts
of
the
antenna.
If
the
antenna
is
only
loaded
with
air
it
will
be
comparatively
large,
high
dielectric
constant
ceramics
result
in
a
much
smaller
form
factor.
The
smaller
the
dimensions
of
the
antenna,
the
more
performance
critical
tight
manufacturing
tolerances
become.
Furthermore,
a
smaller
antenna
will
present
a
smaller
aperture
to
collect
the
signal
energy
from
sky
resulting
in
a
lower
overall
gain
of
the
antenna.
This
is
the
result
of
pure
physics
and
there
is
no
“magic”
to
get
around
this
problem.
Amplifying
the
signal
after
the
antenna
will
not
improve
the
signal
to
noise
ratio.
Figure 26: Quadrifilar Helix Antenna, Sarantel, Ltd.
In
contrast
to
helix
antennas,
patch
antennas
require
a
ground
plane
for
operation.
Helix
antennas
can
be
designed
for
use
with
or
without
a
ground
plane.
For
precision
applications
such
as
surveying
or
timing,
some
very
high
caliber
antenna
systems
exist.
Common
to
these
designs
are
large
size,
high
power
consumption
and
high
cost.
These
designs
are
highly
optimized
to
suppress
multi-path
signals
reflected
from
the
ground
(choke
ring
antennas,
multi-path
limiting
antennas,
MLA).
