Changing
Signal
P
ath
After
Calibration
If
an
y
attenuator
or
other
external
equipmen
t
is
c
hanged
after
calibration,
the
measuremen
t
results
cannot
b e
sp ecied
except
b
y
y
our
o
wn
estimation
of
the
error
con
tribution
of
the
c
hange.
F
or
example,
when
the
p ort
attenuation
is
c
hanged
with
correction
On,
the
CA
UTION:
CORRECTION
MA
Y
BE
INV
ALID
is
display
ed.
The
op erator
m
ust
judge
whether
the
error
is
tolerable
in
the
particular
application
and
ho
w
to
comp ensate
for
the
c
hange.
The
only
reason
to
c
hange
the
in
ternal
attenuators
or
external
equipmen
t
b et
w
een
calibration
and
measuremen
t
is
to
maximize
the
lev
els
under
b oth
conditions,
th
us
minimizing
uncertain
t
y
due
to
noise.
Many
factors
will
en
ter
in
to
the
decision
of
whether
it
is
more
accurate
to
calibrate
at
a
low
signal
lev
el
without
c
hanging
the
setup,
or
c
hange
the
setup
to
optimize
lev
els
for
b oth
calibration
and
measuremen
t.
Changing
the
P
ort
1
or
the
P
ort
2
attenuator
do es
not
seriously
c
hange
the
test
set
mismatch,
directivit
y
,
or
isolation
c
haracteristics,
but
will
c
hange
the
frequency
resp onse
magnitude
and
phase.
This
dierence
in
the
frequency
resp onse
b et
w
een
calibration
and
measuremen
t
can
b e
normalized
using
the
HP
8510
trace
memories.
The
application
question
is:
Do
es
increasing
the
signal
lev
els
during
calibration
improv
e
the
calibration
enough
to
risk
greater
error
con
tributions
p ossible
b
y
c
hanging
the
setup?
Set
the
A
ttenuators
If
only
the
P
ort
1
or
P
ort
2
attenuators
are
c
hanged,
the
follo
wing
pro cedure
can
minimize
the
errors.
1.
Connect
a
short
or
a
thru
and
set
the
P
ort
1
and
P
ort
2
attenuators
for
b est
IF
signal
lev
els
during
calibration.
2.
P
erform
the
appropriate
measuremen
t
calibration.
3.
With
an
appropriate
standard
connected,
set
the
P
ort
1
and
P
ort
2
attenuators
to
the
setting
required
for
op erating
the
test
device.
If
y
ou
view
the
resp onse
of
a
short
circuit,
notice
that
c
hanging
the
P
ort
1
attenuators
has
negligible
eect
on
the
S
11
marker
reading,
and
that
c
hanging
P
ort
2
attenuators
has
negligible
eect
on
the
S
22
marker
reading.
This
is
due
to
the
w
a
y
that
the
attenuators
are
paired.
Both
the
reference
and
the
test
signal
are
c
hanged
an
appro
ximately
equal
amoun
t.
Ho
w
ev
er,
when
viewing
S
21
or
S
12
,
c
hanging
the
P
ort
1
or
P
ort
2
attenuators
osets
the
marker
reading
b
y
the
dierence
in
the
P
ort
1
and
P
ort
2
v
alues.
Store
Trace
Memories
The
main
frequency
resp onse
eects
of
c
hanging
the
attenuators
can
b e
comp ensated
for
b
y
using
the
HP
8510
trace
memories
and
trace
mathematics
as
follows.
1.
Connect
the
thru
used
for
calibration.
Set
the
p ort
attenuators
to
the
v
alue
used
for
measuremen
t
of
the
device.
Rec
hec
k
the
user
parameter
lev
els
then
press
4
S
21
5.
2.
Press
4
DISPLA
Y
5
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
DATA
!MEMORY
to
store
the
S
21
trace
in
default
trace
memory
1.
This
trace
is
the
frequency
resp onse
dierence
of
the
S
21
signal
path
b et
w
een
calibration
and
measuremen
t.
10-6
High
P
o
w
er
Measurements
Содержание 8510
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Страница 12: ...Figure 1 1 HP 8510 Pulsed RF Network Analyzer System Introduction 1 3 ...
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Страница 17: ...Figure 2 2 HP 85110A S Parameter Test Set Signal Flow 2 4 System Description ...
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Страница 27: ...Figure 5 1 System Cable Connections 5 2 Operating the HP 8510 for Pulsed RF Measurements ...
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Страница 72: ...Figure 11 1 Option 008 Domain Stimulus and System Menus Reference Data 11 5 ...
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