Lo Generation And Distribution Circuits; Off-Chip Rf Components; Only For Training And Service Purposes - LG KS20 Operating Instructions 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/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: 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 (U503: ACPM-7381)
The UMTS PA output power is monitored by l power detector circuits(U500 : RTR6275).
This detector voltage can be used for transmitter calibration and monitor to meet RF system
specification.
FL503
L520 C553
1
RX_WCDMA_2100 RX PGND
1nH 2
33p TX ANT
ACMD-7602
C554
SDMY0001301
3p
Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

4
3
VPWR
(1608)
U502
C560
33p
SCDY0003402
33p C561
C563
1.5p
20dB
R518
51
R519
75
R520 R521
91 91
10dB
[Figure 1.5] WCDMA PAM, Duplexer, Coupler
SMPY0015501
C555 C556 C557
10u
220p 100p
ACPM-7381 U503
11
PGND
10 1
VCC2 VCC1
9 2
GND3 RFIN
8 3
RFOUT VMODE1
7 4
GND2 VMODE0
6 5
C564 GND1 VEN
NA C565
C566 100p
100p
As close as possible
PWR_DET
- 25 -
3. TECHNICAL BRIEF
4 5 L522
C559
C558 L521
O1 G3 1
IN
G2 G1
2.7nH
33p 33p 4.7nH
3 2
L524
10nH
10nH
L523
FL504
EFCH1950TDF1
WCDMA_PA_R0
WCDMA_PA_ON
LGE Internal Use Only
WCDMA_2100_TX_OUT