NEO-5
-
Hardware
Integration
Manual
Preliminary
Product
Testing
GPS.G5-MS5-08003-A2
u-blox
proprietary
Page 50
C.3.2 Shielding Sets of Sub-System Assembly
Yet
another
problem
arises
if
multiple
building
blocks
are
combined
in
a
single
system.
shows
a
possible
scenario.
In
this
case,
the
supply
current
traveling
through
the
inductive
ground
connection
between
the
two
sub-systems
will
cause
a
voltage
difference
between
the
two
shields
of
the
sub-system.
The
shield
of
the
other
system
will
then
act
as
a
transmitting
antenna,
radiating
with
respect
to
the
ground
and
shield
of
the
GPS/GALILEO
receiver
and
the
attached
antenna.
Some
other
Electronics
GPS/GALILEO
Receiver
Antenna
Radiation
from
Shield
Ground
Connection
Return
Current
Voltage
Difference
Coaxial
antenna
cable
Figure 38: Two shielded sub-systems, connected by a “poor” ground
This
situation
can
be
avoided
by
ensuring
a
low
inductivity
ground
connection
between
the
two
shields.
But
now,
it
might
be
difficult
to
control
the
path
of
the
ground
return
currents
to
the
power
supply
since
the
shield
is
probably
connected
to
the
supply
ground
at
more
than
one
location.
The
preferred
solution
is
shown
in
Again,
it
is
important
to
have
a
good
(i.e.
low
inductance)
interconnection
between
the
outer
shield
and
the
shielding
ground
of
the
GPS/GALILEO
receiver.
Some
other
Electronics
GPS/GALILEO
Receiver
Power
Supply
Ground
Connection
Antenna
Connection
of
shielding
grounds
Coaxial
antenna
cable
Figure 39: Proper shielding of a sub-system assembly
It
is
clear
that
the
situation
illustrated
in
can
become
complex
if
the
component
“Some
other
electronics”
contains
another
wireless
transmitter
system
with
a
second
antenna,
which
is
referenced
to
the
systems
shielding
ground.
As
already
pointed
out,
in
a
setup
like
this
it
is
important
to
keep
the
shield
free
from
supply
currents
with
high
frequency
spectral
content.
If
there
are
to
be
additional
connections
to
the
shielding
ground,
these
should
be
of
a
highly
inductive
nature.
