Specifications

Another important parameter we can measure when
phase information is available is group delay. In
linear devices, the phase change through the DUT is
linear-with-frequency. Thus, doubling the frequency
also doubles the phase change. An important mea
-
surement, especially for communications system
users, is the rate of change-of-phase-vs.-frequency
(group delay). If the rate of phase-change-vs.-fre
-
quency is not constant, the DUT is nonlinear. This
nonlinearity can create distortion in communica
-
tions systems.
Measurement
Error
Correction
Since we can measure microwave signals in both
magnitude and phase, it is possible to correct for six
major error terms:
q
Source Test Port Match
q
Load Test Port Match
q Directivity
q Isolation
q Transmission Frequency Response
q Reflection Frequency Response
We can correct for each of these six error terms in
both the forward and reverse directions, hence the
name 12-term error correction. Since 12-term error
correction requires both forward and reverse mea-
surement information, the test set must be revers-
ing. “Reversing” means that it must be able to apply
the measurement signal in either the forward or re
-
verse direction.
To accomplish this error correction, we measure the
magnitude and phase of each error signal
(Figure 3-19). Magnitude and phase information ap
-
pear as a vector that is mathematically applied to
the stimulus signal. This process is termed vector er
-
ror correction.
NETWORK ANALYZERS, NETWORK
A PRIMER ANALYZERS
MS462XX OM 3-11
VECTOR ERROR CORRECTION
THEN THE RESULTANT VECTOR IS
APPLIED MATHEMATICALLY, HENCE
MAGNITUDE AND PHASE OF
EACH ERROR SIGNAL IS MEASURED
MAG
PHASE
Figure 3-19. Magnitude and Phase
Measurements