HP 8753D - Page 357

The
TRL
Calibration
Procedure
Requirements
for TRL
Standards
When
building a
set
of
TRL
standards
for
a
microstrip
or
xture
environment,
the
requirements
for
each of
these
standard
types
must
be
satised.
Types
Requirements
THRU
(Zero
length)
No
loss
.
Characteristic
impedance
(Z
0
)
need
not
be
known.
S
21
=
S
12
=
1
6
0

S
11
=
S
22
=
0
THRU
(Non-zero
length)
Z
0
of
the
thru
must
be
the
same
as
the
line
.
(If
they
are
not
the
same,
the
average
impedance
is
used.)
Attenuation
of
the
thru
need
not
be
known.
If
the
thru
is
used
to
set
the
reference
plane
,
the
insertion
phase
or
electrical
length
must
be
well-known
and
specied.
If
a
non-zero
length
thru
is
specied
to
have
zero
delay
,
the
reference
plane
is
established
in
the
middle
of
the
thru.
REFLECT Reection
coecient
(0
)
magnitude
is
optimally
1.0,
but
need
not
be
known.
Phase
of
0
must
known
and
specied
to
within
6
1/4
wavelength
or
6 90

.
During
computation
of
the
error
model,
the
root choice
in
the
solution
of
a
quadratic
equation
is
based
on
the
reection
data. An
error
in
denition
would
show
up
as
a
180

error
in
the
measured
phase
.
0
must
be
identical
on
both
ports
.
If
the
reect
is
used
to
set
the
reference
plane,
the
phase
response
must
be
well-known
and specied.
LINE/MA
TCH
(LINE)
Z
0
of
the line
establishes the
reference
impedance
of
the
measurement
(i.e
.S
11
=
S
22
=
0). The
calibration impedance
is dened
to
be
the
same
as
Z
0
of
the line
.If
the Z
0
is
known but
not the
desired value
(i.e
.,
not
equal
to
50
),
the
SYSTEMS
Z
0
selection
under
the
TRL/LRM
options
menu
is
used.
Insertion
phase
of
the
line
must
not
be
the
same
as
the
thru
(zero
length
or
non-zero
length).
The
dierence
between
the
thru
and
line
must
be
between
(20

and
160

)
6 n
x180

.
Measurement uncertainty
will increase
signicantly
when
the
insertion phase
nears
0
or
an
integer
multiple
of
180

.
Optimal line length is 1/4 wavelength or 90

of insertion phase relative to
the thru at the middle of the desired frequency span.
Usable bandwidth for a single thru/line pair is 8:1 (frequency span:start
frequency).
Multiple thru/line pairs (Z
0
assumed identical) can be used to extend the
bandwidth to the extent transmission lines are available
.
Attenuation of the line need not be known.
Insertion phase must be known and specied within
6 1/4 wavelength or 6 90

.
LINE/MATCH
(MATCH)
Z
0
of the match establishes the reference impedance of the measurement.
0 must be identical on both ports.
6-90 Application and Operation Concepts