Agilent Technologies 4395A - Page 240

Measuring
the
Carrier
to Noise
Ratio
Time
Gated
Spectrum
Analysis
The
time
gated
spectrum
analysis
function
can
be
used
to
measure any
one of
several signals
separated
in
time
(for
example
,
burst modulated,
pulsed RF
,and
time multiplexed).
Using the
gated
sweep
function
allows
the
analyzer
to measure
the spectrum
of a
specic part
of the
signal
or
separate
signals
,
and
mask out
interfering or
transient signals
.In
the gated
sweep
mode
,
the
analyzer
is
triggered
to
start
and
interrupt
sweep selectively
by an
external trigger
signal.
By
controlling
the
external
trigger
signal,
the
analyzer
measures
only the
signals that
are
present
when
the
analyzer
sweeps
.
The
gate
sweep
is
controlled
by
the following
factors:
Trigger
polarity
,
which
determines
which
positive or
negative edge
(level) causes
triggering
Gate
trigger
mode
,
which
selects
one of
two modes
(EDGE or
LEVEL)
Gate
Delay
,
which
determines how
long after
the trigger
signal
the
gate
actually
becomes
active
.
Gate
Length,
which
determines
how long
the gate
is on.
Gate
Trigger
Mode
Two
gate
trigger
modes
(EDGE
and
LEVEL)
are
provided for
the
gate
trigger
to
match
the
trigger
signal
used.
Edge
Mode
.
The
edge
mode
allows
you
to
position
the
gate
relative
to
either
the
rising
or
falling
edge
of
a
TTL
trigger
signal.
The
edge
initiates
the
gate
delay
.
F
or
the
edge
mode
,
the
gate
sweep
is
controlled
by
the
following
factors:
Trigger
polarity
,
which
selects
the
edge
(positive
or
negative)
to
initiate
the
start
point of
the
gate
sweep
.
At
the
start
point,
the
edge
initiates
the
gate
delay
.
Gate
Delay
,
which
determines
how
long
after
the
trigger
signal
the
gate
actually
becomes
active
.
Gate
Length,
which
determines
how
long
the
gate
is
on.
Figure 8-21. Edge Mode
8-38 Analyzing the Measurement Results