Lo Generation And Distribution Circuits; Off-Chip Rf Components - LG KU380 Service Manual

3.4 LO generation and distribution circuits

The integrated LO generation and distribution circuits are driven by internal VCOs to support various
modes to yield highly flexible quadrature LO outputs that drive all GSM and UMTS band upconverters
and downconverters; with the help of these LO generation and distribution circuits, zero-IF architecture
is employed in all GSM and UMTS band receivers and transmitters to translate the signal directly from
RF to baseband and from baseband to RF.
Two fully functional fractional-N synthesizers, including VCOs and loop filters, are integrated within the
RTR6275 IC. The first synthesizer (PLL1) creates the transceiver LOs that support the UMTS
2100/1900/1800 transmitter, and all four GSM band receivers and transmitters including: GSM 850,
GSM 900, GSM 1800, and GSM 1900. The second synthesizer (PLL2) provides the LO for the UMTS
2100/1900/1800 receiver. An external TCXO input signal is required to provide the synthesizer
frequency reference to which the PLL is phase and frequency locked. The RTR6275 IC integrates
most of PLL loop filter components on-chip except two off-chip loop filter series capacitors, and
significantly reduces off-chip component requirement. With the integrated fractional-N PLL
synthesizers, the RTR6275 has the advantages of more flexible loop bandwidth control, fast lock time,
and low-integrated phase error

3.5 Off-chip RF Components

3.5.1 WCDMA PAM (U104: AWT6277R)
The UMTS PA output power is monitored by l power detector circuits(U101 : RTR6275) .
This detector voltage can be used for transmitter calibration and monitor to meet RF system
WCDMA
L123
1.8nH
FL102
4 1
PGND RX
3 2
ANT TX
ACMD-7602
L126
12nH
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
NEAR TO PAM
+VPWR
C155
10p
3.9p
C154
C157
NA
20dB
U103
CP0402A1950DNTR
PWR_DET
R122
R123 R124
47
130 130
7dB
[Figure 1.5] WCDMA PAM, Duplexer, Coupler
3. TECHNICAL BRIEF
NEAR TO PAM
+VPWR
C149 C151 C152
4.7u
1u 1u
AWT6277R U104
11
GND5
10 1
VCC2 VCC1
9 2
GND4 RFIN
8 3
RFOUT GND1
7 4
GND3 VMODE
6 5
GND2 VREF
L127 NEAR TO PAM
15nH
C158
100p
- 25 -
C148
8.2p
FL101
EFCH1950TDF1
4 5
O1 G3
1
L122
L121 IN
G2 G1
NA
5.6nH
3 2
PA_R0
TR100
KRX102U
PA_ON
VREG_TCXO_2.85V
C162
100p
L131
2 2nH
LGE Internal Use Only