LG 410G Service Manual page 26

VBAT
C407
C406
0.01u
0.01u
L411
C415 3.3nH
0.5p
L410
2.7nH
C419
DNI
Figure 3-9-2. PAM (Power Amplifier Module) interface
The digital transmitter architecture is based on a fractional-N sigma-delta synthesizer for constant
envelope GMSK modulation. This configuration allows a very low power design with a reduced
external component count.
The modulation is transferred between baseband- and RF-part of the PMB7880 via a digital
interface signal into the digital modulator. The following Gaussian filter shapes the digital data
stream for the GMSK modulation. Additionally a pre-distortion filter compensates the attenuation of
the PLL transfer function resulting in a very low distortion at the transmit output. The filtered digital
data stream is scaled appropriately and added to the channel word.
This sum is fed into the MASH modulator. The output of the MASH modulator is a sequence of
integer divider values representing the high resolution fractional input signal. This sequence
controls the MMD (multi modulus divider) at a sample rate of 26MHz. Thus a tightly controlled
frequency modulation of the VCO is achieved.
Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes
ECCH0003002
C2012JF1A106ZT
C408 C405
C409
0.01u
39p 10u
15 3
DCS_PCS_OUT DCS_PCS_IN
C417
11 4
U400
EGSM_OUT EGSM_IN
1p
SKY77318
19 18
RSVD_GND ENABLE
21 1
P_GND BS
C421
0.5p
R400
15K
C400
close to DBB
68p
L400
3.3nH
C402
1.5p
R403
10
C414
1.5p
C422 C423
0.5p 27p
-23-
- 27 -
3. H/W Circuit Description
TX_RAMP
TXHB
C403
VDDRF1
1.5p L401
1nH
C410
15p
C412
180p
L403
18nH
C413
TXLB
L404 47p C418
DNI
10nH
R404 47
PA_EN
R405 47
PA_BAND
LGE Internal Use Only