Agilent Technologies 4395A - Page 350

System
Error
Model
System Error
Model
Any
measurement
result
is
the vector
sum of
the actual
test device
response plus
all error
terms
.
The
precise
eect of
each error
term depends
upon its
magnitude and
phase relationship
to
the
actual
test
device response
. When
the phase
of an
error response
is not
known, phase
is
assumed
to
be
worst case
(0 or
180 degrees).
Random errors
such as
noise and
connector
repeatability
are
generally
combined
in a
root-sum-of the
squares (RSS)
manner.
The
error
term
related
to
thermal
drift
is combined
on a
typical basis
as shown
in
each
uncertainty
equation
given
in
the
following
paragraphs.
Figure
11-23
shows
the
error model
for the
analyzer with
the 85046A/B
S-parameter
test
set.
This
error
model
shows
the relationship
of the
various error
sources in
the
forward
direction
and can
be used
to analyze
overall measurement
performance
.
The
model
for
signal
ow
in
the
reverse
direction
is similar
. Note
the appearance
of
the
dynamic
accuracy
,
noise
errors
,
switch
errors
,
and connector
repeatability terms
in both
the
reection
and
transmission
portions
of
the
model.
Figure 11-23.
4395A/85046A
System Error
Model
T
able
11-2.
P
arameters
of
System
error
Model
A
= Dynamic
A
ccuracy
U
=
Multiplexer
Switching
Uncertainty
(
A
m
=
Magnitude
Dynamic
A
ccuracy) (
U
m
=
Magnitude
Multiplexer
Switching
Uncertainty)
( A
p
= Phase Dynamic A
ccuracy) ( U
p
= Phase Multiplexer Switching Uncertainty)
N
l
= Noise Floor
M
s
= Residual Source Match
N
h
= High Level Noise
M
l
= Residual Load Match
T
sw
= Switch Tracking
C = Residual Crosstalk
M
sw
= Switch P
ort Match
T
r
= Residual Reection Tracking
R
r1
=P
ort 1 Reection Repeatability
T
t
= Residual Transmission Tracking
R
r2
=P
ort 2 Reection Repeatability
S
r1
=P
ort 1 Cable Reection Stability
R
t1
=P
ort 1 Transmission Repeatability
S
r2
=P
ort 2 Cable Reection Stability
R
t2
=Port 2 Transmission Repeatability S
t1
=Port 1 Cable Transmission Stability
T
rd
= Reection Tracking Drift S
t2
=Port 2 Cable Transmission Stability
T
td
= Transmission Tracking Drift D = Residual Directivity
For measurement of one-port devices, set the crosstalk (C), load match (M
l
), transmission tracking (T
t
),
transmission tracking drift (T
td
), port 2 connector repeatability (R
r2
,R
t2
), and port 2 cable stability (S
r2
,S
t2
)
error terms to zero.
11-34 Specications and Supplemental Characteristics