Only For Training And Service Purposes - LG CP150 Service Manual

3. HW Circuit Description
VBAT
C407 C408
C406 C409
0.01u 0.01u
0.01u 39p
L411
C415 3.3nH C417
0.5p 1p
L410
C419 2.7nH C421
DNI 0.5p
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.
LGE Internal Use Only
C400
68p
ECCH0003002
C2012JF1A106ZT
C405
10u
15 3
DCS_PCS_OUT DCS_PCS_IN
11 4
U400
EGSM_OUT EGSM_IN
SKY77318
19 18
RSVD_GND ENABLE
21 1
P_GND BS
C422
0.5p
Figure 3-9-2. PAM (Power Amplifier Module) interface
R400
15K
close to DBB
L400
3.3nH
C402
1.5p
R403
10
C414
1.5p
C423
27p
Copyright © 2008 LG Electronics. Inc. All right reserved.
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TX_RAMP
TXHB
C403
VDDRF1
L401
1.5p
1nH
C410
15p
C412
180p
L403
18nH
C413
TXLB
L404 47p C418
DNI
10nH
R404 47
PA_EN
R405 47
PA_BAND

Only for training and service purposes