Time Domain
Operation (Option
010)
With
Option
010,
the
analyzer can
transform frequency
domain data
to the
time domain
or
time
domain
data
to
the
frequency
domain.
In
normal
operation,
the
analyzer
measures
the characteristics
of a
test device
as a
function
of
frequency
.
Using
a
mathematical
technique
(the
inverse F
ourier transform),
the analyzer
transforms
frequency
domain
information
into the
time domain,
with time
as the
horizontal
display
axis
.
Response
values
(measured
on the
vertical axis)
now appear
separated
in
time
or
distance
,
providing
valuable
insight
into the
behavior of
the test
device
beyond
simple
frequency
characteristics
.
Note
An HP
8753D
can
be
ordered
with
Option
010,
or
the
option
can
be
added
at
a
later
date
using
the
HP
85019B
time
domain
retroît
kit.
The
transform used
by the
analyzer resembles
time
domain
reîectometry
(TDR)
measurements
.
TDR
measurements,
however,
are
made
by
launching
an
impulse
or
step
into
the
test
device
and
observing
the
response in
time
with
a
receiver
similar
to
an
oscilloscope
.
In
contrast,
the
analyzer
makes
swept
frequency
response
measurements
,
and
mathematically
transforms
the
data
into
a
TDR-like
display
.
The
Transform
Menu
The
analyzer's
transform
menu
can
be
accessed by
pressing
4
SYSTEM
5
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TRANSFORM
MENU
.
This
menu
consists
of
the
following
softkeys:
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TRANSFORM
ON
off
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SET
FREQ
LOW
PASS
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LOW PASS
IMPULSE
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LOW
PASS
STEP
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BANDPASS
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WINDOW
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SPECIFY GATE
The analyzer has three frequency-to-time transform modes:
Time domain bandpass mode
is designed to measure band-limited devices and is
the easiest
mode to use
. This mode simulates the time domain response of
an impulse input.
Time domain low pass step mode
simulates the time domain response of a
step input. As in
a traditional TDR measurement, the distance to the discontinuity in the test device
, and the
type of discontinuity (resistive
, capacitive
, inductive) can be determined.
Time domain low pass impulse mode
simulates the time domain response of an impulse
input (like the bandpass mode). Both low pass modes yield better time domain resolution for
a given frequency span than does the bandpass mode. In addition, when using the low pass
modes, you can determine the type of discontinuity. However, these modes have certain
limitations that are deîned in \Time domain low pass," later in this section.
Application and Operation Concepts 6-117
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