HP 8753D - Page 328

Figure
6-43.
Load
Match
E
LF
The
measured
value
,
S
21M
,
consists
of
signal
components
that
vary
as
a
function
of
the
relationship
between
E
SF
and
S
11A
as
well
as
E
LF
and
S
22A
,
so
the
input
and
output
reection
coecients
of
the
test
device
must
be
measured
and
stored
for
use
in
the S
21A
error-correction
computation.
Thus
,
the
test
setup
is
calibrated as
described above
for
reection
to
establish
the
directivity
,
E
DF
,
source
match,
E
SF
,
and
reection
frequency
response
,
E
RF
,
terms
for
the
reection
measurements
.
Now
that
a
calibrated
port
is
available
for
reection
measurements,
the
thru
is
connected
and
load
match,
E
LF
,
is
determined
by
measuring
the
reection
coecient
of
the
thru connection.
Transmission
signal
path
frequency response
is
then
measured
with
the
thru
connected.
The
data
is
corrected
for source
and
load
match
eects
,
then
stored
as
transmission
frequency
response
,
E
TF
.
Note
It
is
very
important
that
the
exact
electrical
length
of
the
thru
be known.
Most
calibration
kits assume
azero
length thru.
For
some
connection
types
such
as
Type-N,
this
implies one
male and
one female
port.
If
the
test
system
requires
a
non-zero
length
thru, for
example,
one with
two
male
test
ports
,
the
exact
electrical
delay
of
the thru
adapter must
be used
to modify
the
built-in
calibration kit
denition of
the
thru.
Isolation,
E
XF
,
represents the
part
of
the
incident
signal
that
appears
at
the
receiver
without
actually passing through the test device (see
Figure 6-44). Isolation is measured with the test
set in the transmission conguration and with terminations
installed at the points where the
test device will be connected.
Application and Operation Concepts 6-61