HP 8753D - Page 396

increased
impulse width.
The eect
of windowing
on
the
step
stimulus
(low
pass
mode
only)
is
a
reduction of
overshoot
and
ringing
at
the
expense
of
increased
rise
time
.
To
select a
window,
press
4
SYSTEM
5
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TRANSFORM MENU
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WINDOW .
A menu
is presented
that
allows
the
selection
of three
window types
(see T
able 6-11
).
T
able
6-11.
Impulse
Width, Sidelobe
Level, and
Windowing V
alues
Window
Type
Impulse
Sidelobe
Level
Low
P
ass
Impulse
Width
(50%)
Step
Sidelobe
Level
Step
Rise
Time
(10
-
90%)
Minimum 0
13
dB
0.60/Freq
Span
0
21
dB
0.45/Freq
Span
Normal 0
44
dB
0.98/Freq
Span
0
60
dB
0.99/Freq
Span
Maximum 0
75
dB
1.39/Freq
Span
0
70
dB
1.48/Freq
Span
NOTE: The
bandpass mode
simulates an
impulse
stimulus
.
Bandpass
impulse
width
is
twice
that
of
low
pass
impulse
width.
The
bandpass
impulse
sidelobe
levels
are
the
same
as
low
pass impulse
sidelobe levels
.
Choose
one
of
the
three
window
shapes
listed
in
T
able
6-11
.
Or
you
can
use
the
knob
to
select
any
windowing
pulse
width
(or
rise
time
for
a
step
stimulus)
between
the
softkey
values
.
The
time domain
stimulus
sidelobe
levels
depend
only
on
the
window
selected.
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MINIMUM
is
essentially
no
window
.
Consequently
,
it
gives
the
highest
sidelobes
.
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NORMAL
(the
preset
mode)
gives
reduced
sidelobes
and
is
the
mode
most
often
used.
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MAXIMUM window
gives
the
minimum
sidelobes
,
providing
the
greatest
dynamic range
.
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USE
MEMORY
on
OFF
remembers
a
user-specied
window
pulse
width
(or
step
rise
time)
dierent
from
the
standard
window
values
.
A
window
is
activated
only
for
viewing a
time domain
response,
and does
not
aect
a
displayed
frequency
domain
response
.
Figure
6-71
shows
the typical
eects of
windowing on
the time
domain response
of a
short
circuit
reection
measurement.
Application and Operation Concepts 6-129