R&S FSV-K70, Руководство пользователя

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Brief Description of Vector Signal Analysis
R&S
®
FSV-K70
56 Operating Manual 1176.7578.02 ─ 09
Note that the gain imbalance is not estimated (and cannot be compensated for) in a
BPSK signal.
Preconditions for Gain Imbalance and Quadrature Error measurements
The distortions "gain imbalance" and "quadrature error" can only be measured without
ambiguity, if the following two conditions are fullfilled:
●
a pattern is detected
●
the modulation is a non-differential, non-rotating QAM or PSK
Otherwise, only the measurement parameter "IQ Imbalance", which is a combination of
the gain imbalance and the quadrature error, is significant.
Quadrature Error
Figure 2-53: Effect of Quadrature Error
The quadrature error is another modulation error which is shown in figure Figure 2-53 .
In this diagram, the I and Q components of the modulated carrier are of identical ampli-
tude but the phase between the two components deviates from 90°.
This error also distorts the coordinates. In the example in figure Figure 2-53 the Q axis
is shifted.
Note that the quadrature error is not estimated (and cannot be compensated for) in a
BPSK signal.
I/Q Imbalance
The effect of quadrature error and gain imbalance are combined to form the error
parameter I/Q imbalance.
 


j
Q I
j
Q I
lin
e g g
e g g
B
 
 

Signal Model, Estimation and Modulation Errors