Only For Training And Service Purposes - LG GT500 Service Manual

3. TECHNICAL DESCRIPTION
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.
ANT
ESD
GSM/EDGE
PA + Ant Sw.
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
LGE Internal Use Only
1930 – 1990 MHz
1805 – 1880 MHz
925 – 960 MHz
869 – 894 MHz
VAPC
GSM850/
824 – 915 MHz
900 Input
PA
DCS/PCS
1710 – 1910 MHz
Input
PA
VBAT
PWM/PFM
VccWPA
Switch
FB
Power
coupler
DET
Power
coupler
DET
2.75 V
VRAD
DET
Figure 3-7-3. WCDMA Receiver Architecture
WCDMA/GSM/GPRS/EDGE TRX
GSM/EDGE
HB
LNA
GSM/EDGE
HB
LNA
GSM/EDGE
LB
LNA
GSM/EDGE
LB
LNA
WCDMA HB
LNA
WCDMA HB
LNA
WCDMA LB
LNA
GSM/
EDGE LB
GSM/
EDGE HB
WDCDCREF
DAC
En RFCtrl1
GSM/EDGE
Control
Logic
AM +
VccWPA
RFCtrl1
RFCtrl1
RFCtrl2
RFCtrl2
Bias En
WCDMA HB
VccWPA
WCDMA HB
WCDMA HB
Bias En
WCDMA LB
VccWPA
XOn
XO
XOp
26MHz
X-tal
- 64 - Copyright © 2009 LG Electronics. Inc. All right reserved.
WRxIA
WRxIB
0
90
WRxQA
WRxQB
EDataStr
A
EDataA
D
EDataC
A
EDataB
D
VCO
÷
VCO
N.M
+
XO
LPF ChP PhD
DAC
DAC
DAC
CLK
Serial DATA
LPF ChP PhD
STROBE
Control
÷
VCO
N.M
WTxIA
WTxIB
0
+
90
WTxQA
WTxQB
MCLK
MCLKSec
CLKREQ

Only for training and service purposes

2.75 V
VRAD
1.8 V
VIO
RADCLK
RADDAT
RADSTR