Only For Training And Service Purposes - LG MG370 Service Manual

3. TECHNICAL BRIEF
C400
10u
(2012 size)
R403
TX_RAMP
1K
L401
1.5nH
C411 C412
NA 1.8p
L402
2.7nH
C417 C418
NA 2.2p
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
C401 C402 C403 C404
12p 0.01u 33p 18p
C408
39p
15
DCS_PCS_OUT DCS_PCS_IN
11
U400
EGSM_OUT EGSM_IN
SKY77318
19
RSVD_GND ENABLE
21
P_GND
Figure 3-9-3. PAM (Power Amplifier Module) interface
C405 C406
27p 0.01u
3
4
18
TXON_PA
1
BS BAND_SEL
C414 C415
27p 27p
Copyright © 2007 LG Electronics. Inc. All right reserved.
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SC400
10
1 11
2 12
3 13
4 14
5 15
6 16
7 17
8 18
9 19
Shield CAN
C409
DCS_PCS_OUT
100p
R404 R405
NA NA
C416
GSM_OUT
100p
R406 R407
NA NA

Only for training and service purposes