Agilent Technologies 4395A - Page 395

Spectrum
Measurement
Basics
Spectrum Measurement
Basics
Detection
Modes
The
analyzer
displays the
value measured
at the
display point
specied by
NOP.
However,
analyzer
sweeps
with
the
resolution
specied
by RBW
. Detection
chooses one
level measured
between
display
points
for
displaying
the
trace.
One of
three detection
modes can
be
selected:
P
ositive
P
eak
Mode
Negative
P
eak Modes
Sample
Mode
These
modes
are
as
described in
the following
subsections.
Positive
and Negative
Peak
Modes
P
ositive
and negative
peak modes
store
signal
maximums
and
minimums
between
the
display
points
,
respectively
,
in
a
data
array.
Sample
Mode
In
the
sample
mode
,
the
signal
value
at
the
display point
is placed
in a
data array
.
Sample
mode
is
used
to
measure
noise
level.
Swept
Spectrum
Analyzers
versus
FFT
Analyzers
Usually
,
two
analyzers
are
used
to
analyze waveforms
transformed
from
the
time
domain
test
signal
to
the
frequency
domain;
one
is
a
swept spectrum
analyzer
and
the
other
is
an
FFT
analyzer
.
When
measuring signals
over
a
wide
frequency
span
with
a
wide
RBW
,
swept
spectrum
analyzers
are better
than FFT
analyzers
.
This
is
true
because
the
FFT
analyzer
requires
a
large
memory
and a
fast AD
converter
to
measure
the
signal
and
therefore
,
is
not
practical.
When
measuring
signals
with
narrow
RBW
,
FFT
analyzers
are
better
than
swept
spectrum
analyzers
because
the
swept
spectrum
analyzer
requires
much
more
time
to
measure
(sweep)
the
signal.
The
FFT
analyzer
can
measure
the
signal
in
very
short
time
.
In
spectrum
analyzer
mode
,
the
4395A
operates
as
a
step
FFT
analyzer
which
supports
high-speed
sweep
throughout
the
entire
RBW
.
Basic Measurement Theory A-19