HP 8753D - Page 125

Non-coaxial Measurements
The
capability
of
making
non-coaxial measurements
is available
with the
HP 8753
family of
analyzers
with
TRL*
(thru-reect-line)
or
LRM*
(line-reect-match) calibration.
For
indepth
information
on
TRL*/LRM*
calibration,
refer
to
Chapter 6,
\Application and
Operation
Concepts
."
Non-coaxial,
on-wafer
measurements
present
a unique
set of
challenges for
error correction
in
the
analyzer:
The
close
spacing
between
the
microwave
probes makes
it dicult
to maintain
a
high
degree
of
isolation
between
the
input
and
the output.
The
type
of device
measured on-wafer
is often
not always
a
simple
two-port.
It
may
be dicult
to make
repeatable on-wafer
contacts due
to
the
size
of
the
device
contact
pads
.
Due
to
the simplicity
of the
calibration standards
, TRL*
or
LRM*
calibrations
may
be
used
for
non-coaxial
applications
such
as on-wafer
measurements.
This
type
of
calibration
with
time
domain
gating
and
a
variety
of probe
styles
can
provide
optimal
accuracy
in
on-wafer
measurements
.
At
frequencies
where
on-wafer
calibration
standards
are
available
,
SOL
T
calibrations
can
also
be
done
and
may
be
preferred
due
to
the
better
accuracy
of
the
SOLT
calibration
method.
F
or
information
on
how
to
perform
TRL*
or
LRM*
calibrations,
refer to
the
section
\TRL*
and
TRM*
Error-Correction"
in
Chapter
5,
\Optimizing
Measurement
Results
."
2-76 Making Measurements