RF9678 データシートの表示（PDF） - RF Micro Devices
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RF9678 Datasheet PDF : 16 Pages
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Preliminary
RF9678
Ref Lvl
-3 dBm
-10
-20
-30
-40
-50
Marker 1 [T1]
-21.97 dBm
380.01503006 MHz
RBW 30 kHz
VBW 300 kHz
SWT
2s
RF Att
Unit
20 dB
dBm
1 [T1]
-21.97 dBm A
380.01503006 MHz
CH PWR
-2.62 dBm
1
ACP Up
-50.30 dB
ACP Low
-49.72 dB
1RM
EXT
-60
-70
-80
-90
cl1
-100
C0
cl1
C0
cu1
cu1
Center 380 MHz
Date:
6.FEB.2001 00:47:49
1.46848 MHz/
Span 14.6848 MHz
Figure 4. W-CDMA Spectral Plot
5
Adjusted Performance
In theory, an ideal quadrature modulator will completely suppress the carrier and sideband signals. In practice, due to
process and packaging effects, real quadrature modulators lack the balance necessary to completely cancel the carrier
and sideband signals. The imbalance caused by process and packaging effects is usually very small and may be cor-
rected by preadjusting the input signals to the modulator. This process of adjusting the input signals to minimize the car-
rier and sideband suppression is known as optimization.
Sideband suppression results from the summing together of the I and Q channel mixer outputs. In an ideal quadrature
modulator, at the summing point the sideband signals from the I and Q mixers are 180° out of phase and have equal
magnitudes. In a real modulator, the amplitude and phase are not exactly balanced and 100% cancellation does not
occur. The problem is corrected by introducing amplitude and phase corrections before applying a signal to the modula-
tor. Maximum sideband suppression is achieved when the amplitude and phase errors introduced by the modulator are
compensated for.
Complete carrier suppression occurs when there is no DC offset between the mixer signal input and the mixer reference
voltage (i.e., ISIG+ and ISIG-). In real devices, zero DC offset is difficult to achieve. This problem is corrected by intro-
ducing a DC offset of equal and opposite magnitude before applying the signal to the modulator. The internal error is
thereby canceled and maximum carrier suppression is achieved.
Rev A4 010622
5-97
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