1.
Follow
the procedure
in \Measuring
Electrical Length."
2.
To
increase the
scale resolution,
press:
4
SCALE
REF
5
N
N
N
N
N
N
NN
NN
NN
NN
NN
NN
N
N
N
N
N
N
N
N
N
N
N
SCALE
DIV
and
turn
the front
panel knob
or enter
avalue
from the
front panel
keypad.
3.
T
o
use
the
marker
statistics
to
measure
the
maximum
peak-to-peak
deviation
from
linear
phase
,
press:
4
MARKER F
CTN
5
NN
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
NN
NN
NN
N
N
N
N
N
N
N
N
N
N
N
N
N
N
MKR
MODE
MENU
NN
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
NN
NN
N
STATS
ON
4.
A
ctivate
and
adjust
the
electrical
delay
to
obtain
a
minimum
peak-to-peak
value.
Note
It
is possible
to use
delta
markers
to
measure
peak-to-peak
deviation
in
only
one
portion of
the trace
,
see
\T
o
Calculate
the
Statistics
of
the
Measurement
Data"
located earlier
in this
Chapter
.
Figure
2-31. Deviation
From
Linear
Phase
Example
Measurement
Group Delay
The phase
linearity of
many
devices
is
specied
in
terms
of
group
or
envelope
delay
.
The analyzer
can translate
this
information
into
a
related
parameter
,
group
delay
.
Group
delay is
the transmission
time through
your
device
under
test
as
a
function
of
frequency
.
Mathematically,
it is
the derivative
of
the
phase
response
which
can
be
approximated
by
the
following ratio:
0
1
/(360 * 1F)
where 1
is the dierence in phase at two frequencies separated by 1F
. The quantity 1F is
commonly called the \aperture" of the measurement. The analyzer calculates group delay from
its phase response measurements
.
The default aperture is the total frequency span
divided by the number of points across the
display (i.e
. 201 points or 0.5% of the
total span in this example).
1. Continue with the same instrument settings and measurements as
in the previous procedure
,
\Deviation from Linear Phase."
2. To view the measurement in delay format, as shown in Figure 2-32, press:
4
FORMAT
5
NNNNNNNNNNNNNNNNN
DELAY
4
SCALE REF
5
NNNNNNNNNNNNNNNNNNNNNNNNNNNNN
SCALE DIV
4
*
54
*
5
Making Measurements 2-33
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