LG GT500 - Page 63

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LGE Internal Use Only Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3. TECHNICAL DESCRIPTION
Figure 3-7-3. WCDMA Receiver Architecture
3.7.2.2. Receiver Part
The W-CDMA receiver architecture is a direct down-conversion Zero Intermediate Frequency (ZIF)
receiver with integrated low-pass channel filter, i.e. the front-end receiver converts the aerial RF signal
from W-CMDA band I down to a ZIF. The first stage consists of one single-ended low noise amplifier (LNA)
with a 16 dB gain step. This LNA is followed through an external filter by an IQ down-mixer which consists of
a mixer in parallel driven by quadrature out-of-phase LO signals. The In phase (I) and Quadrature phase (Q)
ZIF signal are then low pass filtered to provide protection from high frequency offset interferer fed into the
channel filter.
The front-end zero IF I and Q outputs are applied to the integrated low-pass channel filter with a provision
for 4 x 8 dB gain steps in front of the filter. The filter is a self-calibrated 6 pole, 2 zero filter with a cut-off
frequency around 2.15 MHz and a second order group delay compensation (2 poles, 2 zeroes). Once filtered,
the zero IF I and Q signals are further amplified with provision of 31 x 1 dB steps and DC offset
compensation.
The zero IF output buffer provides close rail-to-rail outputs signal.
GSM/EDGE
PA + Ant Sw.
ANT
VAPC
RADCLK
RADDAT
RADSTR
VBAT
2.75 V
VRAD
1.8 V
VIO
PA
PA
GSM850/
900 Input
DCS/PCS
Input
ESD
2.75 V
VRAD
LNA
LNA
LNA
LNA
LNA
A
D
A
D
0
90
LPF
+
ChP PhD
÷
N.M
VCO
LPF ChP PhD
÷
N.M
+
0
90
+
DAC
DAC
XO
DAC
VCO
VCO
LNA
LNA
WCDMA LB
WCDMA HB
WCDMA HB
WCDMA HB
CLK
DATA
STROBE
Serial
Control
WTxQB
WTxQA
WTxIB
WTxIA
GSM/EDGE
AM
DAC
RFCtrl1
RFCtrl2
RFCtrl1
RFCtrl2
GSM/
EDGE HB
GSM/
EDGE LB
WCDMA LB
WCDMA HB
WCDMA HB
GSM/EDGE
LB
GSM/EDGE
LB
GSM/EDGE
HB
GSM/EDGE
HB
WRxIA
WRxIB
WRxQB
WRxQA
EDataA
EDataB
EDataC
EDataStr
WCDMA/GSM/GPRS/EDGE TRX
MCLK
CLKREQ
MCLKSec
XO
XOn
XOp
26MHz
X-tal
VccWPA
VccWPA
Power
coupler
Power
coupler
VccWPA
VccWPA
Bias
DET
En
DET
Bias
DET
En
UL: 1920 – 1980 MHz
DL: 2110 – 2170 MHz
UL: 1749.9 – 1784.9 MHz
DL: 1844.9 – 1879.9 MHz
UL: 830 – 840 MHz
DL: 875 – 885 MHz
824 – 915 MHz
1710 – 1910 MHz
1930 – 1990 MHz
1805 – 1880 MHz
925 – 960 MHz
869 – 894 MHz
WDCDCREF
FB
Switch
PWM/PFM
En
Control
Logic
RFCtrl1