Anritsu 37 C Series, Operation Manual, Page: 123 / 603

ables are not completely correctable. However, some of them can be
minimized by careful control. For instance: temperature effects can be
reduced by room temperature control, calibration variables can be re-
duced through improved technique and training, and frequency errors
can be virtually eliminated by the fully synthesized internal source.
We know that adapters and cables degrade the basic directivity of the
system, but these errors are compensated by vector error correction.
In general, transmission measurement errors are source match, load
match, and tracking; while reflection measurement errors are source
match, directivity, and tracking.
Error modeling and flowgraphs are techniques used to analyze the er-
rors in a system. Error models describe the errors, while flowgraphs
show how these errors influence the system. Error models (Figure 7-5)
can become quite complex.
The 37XXXC offers a selection of calibration possibilities depending on
the user’s needs. These possibilities are as follows:
q
Frequency Response
q
Reflection Only—1 Port
q
1 Path, 2 Port
q
12 Term—2 Port, Both Directions
These calibration types are described below.
Frequency Response: Corrects for one or both of the transmission er-
ror terms associated with measurements of S21, S12, or both
DISCUSSION MEASUREMENT CALIBRATION
7-6 37XXXC OM
RANDOM ERRORS
Frequency
Repeatability
Noise
Connector Repeatability
Temperature/Environmental
Changes
Calibration Variables
TRANSMISSION MEASUREMENT
ERRORS
Source Match
Load Match
Tracking
INTERNAL SYSTEM ERRORS
RF Leakage
IF Leakage
System Interaction
DIRECTIVITY, SOURCE MATCH,
AND TRACKING ERRORS
DISTORTED MEASUREMENT
S
11M
E
D
S
11A
E
S
Figure 7-5. Example of Error Modeling
ERRORS REDUCED BY CALIBRATION
Directivity
Source Match
Load Match
Frequency Sensitivity (Tracking)
Isolation