HP 8753D - Page 367

Alternate and
Chop Sweep
Modes
Y
ou can
select the
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ALTERNATE
Aand
B or
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CHOP
A and
B softkey
within the
Correction
More
menu
to
activate
either one
or the
other sweep
modes.
For
information about
sweep
types
,
refer
to
\Sweep
Type Menu,"
located earlier
in this
chapter.
Alternate
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ALTERNATE
A
and
B
measures
only
one
input
per frequency
sweep,
in order
to
reduce
unwanted
signals
,
such
as
crosstalk
from
sampler
A
to
B
when
measuring
B/R.
Thus
,
this mode
optimizes
the
dynamic
range
for
all
four
S-parameter
measurements
.
The
disadvantages
of
this
mode
are
associated
with
simultaneous
transmission/reection
measurements
or
full
two-port
calibrations:
this
mode
takes
twice
as
long
as
the chop
mode to
make
these
measurements
.
Chop
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CHOP
A
and
B
is
the
default
measurement
mode
.
This
mode
measures
both
inputs
A
and
B
during each
sweep.
Thus
,
if
each
channel
is
measuring
a
dierent
parameter
and
both
channels
are displayed,
the chop
mode oers
the
fastest
measurement
time
.
This
is
the
preferred
measurement mode
for full
two-port
calibrations
because
both
inputs
remain
active
.
The disadvantage
of this
mode
is
that
in
measurements
of
high
rejection
devices
greater
than
85 dB
,such
as
lters
with
a
low-loss
passband,
maximum
dynamic
range
may
not
be
achieved.
Figure
6-56
shows
the
alternate
sweep
mode
(bold
trace)
overlaying
the
chop
sweep
mode
in
a
band-pass
lter
measurement.
Note
the
dierence
in
the
crosstalk
levels
between
the
two
modes
.
Figure 6-56. Alternate and Chop Sweeps Overlaid
6-100 Application and Operation Concepts