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that
reduces
the
amplitude
of
high-frequency
signals
(noise).
When
coupled,
the
sweep
time
changes
as
the
resolution
or
video
bandwidth,
or
span
changes
.
When
uncoupled,
the
UNCAL
indicator
appears
at
the
right
side
of
the
graticule
when
accuracy
is
aected
by
the
new
settings
.
Limiting
the
signal
level
at
the
mixer
input
controls
accuracy
by
avoiding
gain
compression.
T
o
limit
signal
levels
at
the
input
mixer
,
the
input
attenuation
is
coupled
to
the
reference
level.
When
coupled,
the
attenuation
increases
as
the
reference
level
increases
.
The
limit
can
be
changed
to
increase
dynamic
range
.
The
video
bandwidth
is
coupled
to
the
resolution
bandwidth,
and
the
resolution
bandwidth
is
also
coupled
to
the
span.
Set
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
VID
BW
AutoMan
and
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
RES
BW
AutoMan
to
automatic
to
establish
the
coupling.
Resolving
Closely
Spaced
Signals
Some
measurements
require
adjustment
of
the
resolution
bandwidth
(or
IF)
lter
.
The
spectrum
analyzer
traces
the
shape
of
its
IF
lter
as
it
tunes
past
a
signal.
Thus
,
if
two
equal-amplitude
signals
are
close
enough
in
frequency
,
the
lter
shapes
can
fall
on
top
of
one
another
and
appear
as
a
single
response
.
If
two
signals
are
not
equal
in
amplitude
but
are
still
close
together
,
the
smaller
signal
can
be
hidden
under
the
response
of
the
larger
one
.
T
o
resolve
two
signals
of
equal
amplitude
,
the
resolution
bandwidth
must
be
less
than
or
equal
to
the
frequency
separation
of
the
two
signals
.
F
or
example
,
to
resolve
two
signals
of
equal
amplitude
with
a
frequency
separation
of
1
kHz,
a
resolution
bandwidth
of
1
kHz
or
less
should
be
used.
Phase
noise
,
seen
along
the
lower
skirt
of
the
displayed
response
,
can
also
aect
resolution.
Viewing
Low-Level
Signals
Low-level
signals
hidden
by
the
analyzer
noise
oor
can
be
viewed
using
several
functions
,
all
accessed
by
NNNNNNNNNNNNNNNNNNNNNNN
BW,
Swp
.
Decrease
the
resolution
bandwidth
(
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
RES
BW
AutoMan
).
The
noise
oor
drops
10
dB
as
the
resolution
bandwidth
is
narrowed
by
a
factor
of
10.
However
,
to
maintain
amplitude
accuracy
,
the
sweep
time
should
be
set
to
automatic
to
activate
coupling.
Decrease
the
video
bandwidth
(
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
VID
BW
AutoMan
).
Again,
to
maintain
amplitude
accuracy
,
the
sweep
time
should
be
set
to
automatic
to
activate
coupling.
Use
video
averaging
(
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
VID
AVG
On
Off
).
The
video-averaging
function
averages
the
amplitude
values
contained
in
a
sweep
with
the
values
obtained
in
the
previous
sweep
.
Since
the
video-averaging
function
processes
stored
trace
data,
amplitude
accuracy
is
not
aected
by
the
sweep-time
setting.
Reduce
the
input
attenuation
(
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
ATTEN
AutoMan
).
Reduce
the
input
attenuation
with
caution.
Signals
that
are
not
displayed
in
narrow
spans
might
still
be
present
at
the
input.
Reducing
the
input
attenuation
increases
the
signal
level
to
the
spectrum
analyzer
internal
components
,
which
are
damaged
permanently
by
30
dBm
levels
or
greater
.
F
or
this
reason,
0
dB
input
attenuation
can
be
activated
with
the
numeric
keypad
only
.
Overview
1-13
Содержание 70000 series
Страница 42: ...Auxiliary Measurement Indicators Figure 1 8 Auxiliary Measurement Indicators Overview 1 19 ...
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Страница 346: ...Figure A 2 Simpli ed Lightwave Signal Analyzer Block Diagram Theory of Operation A 3 ...
Страница 366: ...Figure B 6 HP 70620A B Preampli er and HP 70621A Preampli er Front View Input and Output Ports B 11 ...
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