Exfo PSO-200 Optical Modulation Analyzer Uživatelský manuál Strana 262

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Measurement Definitions
254 PSO-200
Measurements for Constellation Charts
Phase Error
The phase error (EP) describes the deviation of phase from the ideal
reference vector, illustrated in the graph. It is computed according to:
IQ Gain Imbalance
The gain imbalance describes the ratio between the I and Q part of the
signal and is computed according to:
The diagram below illustrates a signal with IQ gain imbalance and the
corresponding ideal reference vectors.
In-Phase Error
The in-phase error (EI) is the rms deviation of the I component of the error
vectors, denoted I in the graph. It is calculated according to:
given in percent to the magnitude of the longest reference vector.
EP
rms
1
N
----
I
meas
n()
Q
meas
n()
----------------------


atan
I
ref
rn()
Q
ref
rn()
------------



atan



2
n 1=
N
deg=
GI 20
1
N
----
I
meas
n() I
ref
rn()
Q
meas
n() Q
ref
rn()
--------------------------------------



2
n 1=
N
log dB=
EI
rms
1
N
----
I
meas
n() I
ref
rn()

2
n 1=
N
100 %rms=
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