Specifications

Understanding
the
Calibration
System
Measurement errors must be reduced by a process
that uses calibration standards. The standards most
commonly used are Opens, Shorts, and Z
0
(Charac
-
teristic Impedance) Loads. In conjunction with a
through connection, these standards can correct for
the major errors in a microwave test system. These
errors are Directivity, Source Match, Load Match,
Isolation, and Frequency Tracking (reflection and
transmission).
Calibration also corrects for many internal system
errors, such as RF leakage, IF leakage, and system
component interaction.
Random errors such as noise, temperature, connec
-
tor repeatability, DUT sensitive leakages, frequency
repeatability, and calibration variables are not com
-
pletely correctable. However, some of them can be
minimized by careful control. For instance: tempera-
ture effects can be reduced by room temperature
control, calibration variables can be reduced
through improved technique and training, and fre-
quency 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 com-
pensated by vector error correction.
In general, transmission measurement errors are
source match, load match, and tracking; while re
-
flection measurement errors are source match,
directivity, and tracking.
MEASUREMENT CALIBRATION MEASUREMENT
DISCUSSION CALIBRATION
7-6 MS462XX OM
ERRORS REDUCED BY CALIBRATION
l
Directivity
l
Source Match
l
Load Match
l
Frequency Sensitivity (Tracking)
l
Isolation
INTERNAL SYSTEM ERRORS
l
RF Leakage
l
IF Leakage
l
System Interaction
RANDOM ERRORS
l Frequency
l Repeatability
l Noise
l
Connector Repeatability
l
Temperature/Environmental
Changes
l
Calibration Variables
TRANSMISSION MEASUREMENT
ERRORS
l
Source Match
l
Load Match
l
Tracking