Anritsu 37 C Series, Руководство по эксплуатации, Страница: 187 / 603

In the discussion on calibration we saw that the calibration compo-
nents establish the reference plane and determine the quality of the
measurement. If we have a good Open, Short and Z
0
load to place at
the end of a microstrip line, we can calibrate the system at the point of
measurement.
Figure 8-24 shows some of the special test-fixture calibration stan-
dards that are available.
These special calibration kits are far from perfect, but they are supe-
rior to our perfect transmission line assumption.
You may also have heard of the probe stations built to permit on-wafer
calibration measurements.
The Open, Short, termination approach provides three known stan-
dards that permit the analyzer to solve for three unknowns (Figure
8-25).
37XXXC OM 8-27
MEASUREMENTS ACTIVE DEVICE
APPROACH NUMBER 1
CALIBRATE THE FIXTURE
Special Calibration Devices Re-
quired
SPECIAL CALIBRATION DEVICES
PROBLEMS
Opens Are Difficult-Radiation Ef-
fects
Good Terminations Are Hard to
Find,
20-30 db Is Often the Best That We
Can Do and This Determines the
“Effective Directivity”
ON-WAFER CALIBRATION
Calibration Standards Are on a
Wafer
T H R U L I N E
O F F S E T S H O R T
O P E N
O F F S E T S H O R T
5 0 O H M
1 8 0 / 8 2 - S C 2 4 0 / 5 2 - S C
2 4 0 / 5 2 - O C
Figure 8-24. Special Test Fixtures
O P E N C I R C U I T
( I N A I R )
5 0 O H M
T E R M I N A T I O N
S H O R T
C I R C U I T
P R O B E
5 0 O H M
T H R O U G H L I N E
P R O B E
P R O B E
1 0 0 O H M
1 0 0 O H M
P R O B E P R O B E
Figure 8-25. Solving for Unknowns