LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
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/EDGE and UMTS band
upconverters and downconverters; with the help of these LO generation and distribution circuits, true
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: GSM850,
GSM900, DCS1800, and PCS1900. 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 onchip 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 UMTS PAM (U105: AWT6277R)
The UMTS PA output power is monitored by power detector circuits (U101 : RTR6275) . This detector
voltage can be used for transmitter calibration and monitor to meet RF system specification.
3. TECHNICAL BRIEF
- 27 -
[Figure 1.5] UMTS PAM, Duplexer, Coupler
20dB
8 dB
NA
C165
100p
C163
C160
22u
51
R124
L122
NA
100
R126
2
4
5
3
1
Q100
KRX102E
C162
0.01u
15nH
L123
2
RFIN
RFOUT
8
VCC1
1
10
VCC2
4
VMODE
VREF
5
AWT6277R
U105
GND1
3
GND2
6
7
GND3
9
GND4
GND5
11
5.6p
C169
C161
56p
SCDY0003403
50OHM
4
3
COUP
2
IN
1
OUT
C173
100p
U104
R123
68
C159
8.2p
1.8p
C170
L128
4.7nH
L124
3.3nH
L126
8.2nH
EFCH1950TDF1
FL104
G1
2
G2
3
G3
5
IN
1
O1
4
R125
100
1u
C164
FL103
ANT
2
1
GND1
GND2
4
8
GND3
GND4
9
GND5
6
GND6
3
7
RX
5
TX
SAYZY1G95EB0B00
WCDMA_2100_TX_OUT
PA_ON
VREG_TCXO_2.85V
+VPWR
PA_R1
PWR_DET
Содержание U990
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