Service manual

WLAN TX Measurements
R&S
®
FSV-K91/91n/91ac/91p
34Operating Manual 1176.7649.02 ─ 04
 




1
0
REAL
1
ˆ
N
v
I
r(v)
N
o
(24) (3 - 16)
 




1
0
IMAG
1
ˆ
N
v
Q
r(v)
N
o
(25) (3 - 17)
where r(v) is the measurement signal which has been corrected with the estimates of
the timing-, frequency- and phase offset, but not with the estimates of the IQ-imbalance
and IQ-offset
With these values the IQ-imbalance of the I-branch and the IQ-imbalance of the Q-
branch are estimated in a non-linear estimation in a second step:
 




1
0
ˆ
REAL
1
ˆ
N
v
II
or(v)
N
g
(26) (3 - 18)
 




1
0
ˆ
IMAG
1
ˆ
N
v
QQ
or(v)
N
g
(27) (3 - 19)
Finally, the mean error vector magnitude can be calculated with a non-data-aided cal-
culation:
(28) (3 - 20)
The instant error vector magnitude is the error signal magnitude normalized by the root
mean square value of the estimate of the measurement signal power:
(29) (3 - 21)
The advantage of this method is that no estimate of the reference signal is needed, but
the IQ-offset and IQ-imbalance values are not estimated in a joint estimation proce-
dure. Therefore, each estimation parameter is disturbing the estimation of the other
Signal Processing of the IEEE 802.11b Application