HP 8753D - Page 210

Frequency
Drift
Minute
changes
in
frequency
accuracy
and
stability
can
occur
as
a result
of temperature
and
aging
(on
the
order
of
parts
per
million).
If you
require greater
frequency accuracy
,do
the
following:
Override
the
internal
crystal
with
a
high-stability
external
source,
frequency standard,
or (if
your
analyzer
is
equipped
with
Option
1D5)
use
the
internal
frequency standard.
P
erformance
V
erication
Y
ou
should
periodically check
the accuracy
of the
analyzer
measurements
,
by
doing
the
following:
perform
a measurement
verication at
least once
per
year
Refer
to the
HP 8753D
Service Guide
for
the
measurement
verication
procedure
.
Reference
Plane
and
P
ort
Extensions
Use
the
port
extension
feature
to
compensate
for
the
phase
shift
of
an
extended
measurement
reference
plane
,
due
to
such
additions
as
cables
,
adapters
,
and
xtures
,
after
completing
an
error-correction
procedure
(or
when
there
is
no
active
correction).
Using
port
extensions
is
similar
to
using
electrical
delay
.
However
, using
port extensions
is
the
preferred
method
of
compensating
for
test
xture
phase
shift.
T
able
5-1 explains
the dierence
between
port
extensions
and
electrical
delay
.
T
able
5-1.
Dierences
between
PORT
EXTENSIONS
and
ELECTRICAL
DELAY
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PORT
EXTENSIONS
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ELECTRICAL
DELAY
Main
Eect
The
end
of
a
cable
becomes
the
test
port
plane
for all
S-parameter measurements
.
Compensates
for
the
electrical
length
of
a
cable.
Set
the
cable's
electrical length
x1
for
transmission.
Set
the
cable's
electrical
length
x
2
for
reection.
Measurements
Aected
All
S-parameters
.
Only
the
currently
selected
S-parameter
.
Electrical
Compensation
Intelligently
compensates
for 1
times
or
2
times the cable's electrical delay
, depending
on which S-parameter
is computed.
Only
compensates
for electrical
length.
You can activate a port extension by pressing
4
CAL
5
NNNNNNNNNNNNNN
MORE
NNNNNNNNNNNNNNNNN
NNNNNNNNNNNNNNNNNNNNNNNNN
NNNNN
PORT EXTENSIONS
NNNNNNNNNNNNNNNNN
NNNNNNNNNNNNNNNNNNNNNNNN
EXTENSIONS ON
.
Then enter the delay to the reference plane
.
Optimizing Measurement Results 5-3