HP 8753D - Page 354

line
standard becomes
the measurement
reference and,
therefore
,
has
to
be
assumed
ideal
(or
known
and dened
precisely).
At
this point,
the
forward
and
reverse
directivity
(E
DF
and
E
DR
),
transmission tracking
(E
TF
and
E
TR
),
and reection
tracking
(E
RF
and
E
RR
)
terms may
be
derived
from
the
TRL
error
terms
. This
leaves
the
isolation
(E
XF
and
E
XR
),
source match
(E
SF
and
E
SR
)
and load
match
(E
LF
and
E
LR
)
terms to
discuss.
Isolation
Two
additional
measurements
are
required
to
solve
for
the
isolation
terms
(E
XF
and
E
XR
).
Isolation
is
characterized
in
the
same
manner
as
the
Full
2-port
calibration.
F
orward
and
reverse
isolation
are
measured
as
the
leakage
(or
crosstalk)
from
port
1
to port
2 with
each port
terminated.
The
isolation
part
of
the
calibration
is
generally
only
necessary
when
measuring
high
loss
devices
(greater
than
70
dB).
Note
If
an
isolation
calibration
is performed,
the xture
leakage must
be the
same
during
the
isolation
calibration and
the measurement.
Figure 6-52.
8-term TRL
error model
and generalized
coecients
Application and Operation Concepts 6-87