CDM-750 Advanced High-Speed Trunking Modem
Revision 2
Appendix D
MN-CDM750
D–3
This
performance
is
achieved
through
advanced
signal
processing
algorithms
that
provide
superior
cancellation
while
tracking
and
compensating
for
the
following
common
link
impairments:
1)
Time
varying
delay:
In
addition
to
the
static
delays
of
the
electronics
and
the
round
‐
trip
delay
associated
with
propagation
to
the
satellite
and
back,
there
is
a
time
‐
varying
component
due
to
movement
of
the
satellite.
The
CnC
module
tracks
and
compensates
for
this
variation.
2)
Frequency
offset
and
drift:
Common
sources
are
satellite
Doppler
shift,
up
and
down
converter
frequency
uncertainties,
and
other
drift
associated
with
the
electronics
in
the
CDM
‐
750
itself.
The
CnC
module
tracks
and
compensates
for
this
frequency
offset
and
drift.
3)
Atmospheric
effects:
Fading
and
scintillation
can
affect
amplitude,
phase,
and
spectral
composition
of
the
signal
and
the
degree
to
which
it
correlates
with
the
original
signal.
The
CnC
module
tracks
and
compensates
for
these
atmospheric
related
impairments.
4)
Link
Asymmetries:
Various
asymmetries
in
the
forward
and
return
link
can
produce
differences
in
the
relative
power
of
the
two
received
signal
components.
These
can
be
both
deterministic
(static)
or
random
(and
time
varying).
An
example
of
the
former
would
be
the
differences
resulting
from
antenna
size/gain
variations
between
the
two
ends
of
the
link.
An
example
of
the
latter
would
be
transient
power
differences
due
to
different
levels
of
atmospheric
fading
in
the
uplinks.
CnC
compensates
for
the
asymmetries,
up
to
a
certain
extent.
Figure D-1. Conceptual Block Diagram
Содержание CDM-750
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Страница 224: ...CDM 750 Advanced High Speed Trunking Modem Revision 2 Appendix A MN CDM750 A 4 Notes...
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