LG LG-UD90c, Service Manual

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LG-KG90C
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1. RF Transmit/Receive Part
1.1 Overview
The Tx and Rx part employs the Direct-Conversion system. The Tx and Rx frequencies are
824.04~848.97 and 869.04~893.97. RF signals received through the antenna are seperated by the
duplexer.
RF Signal fed into the YGHF-D010A(RF onechip module). The RF signal is changed into baseband
signal directly. Then, this signal is changed into digital signal by the analog to digital converter (ADC,
A/D Converter), and the digital circuit part of the MSM(Mobile Station Modem) 6100 processes the
data from ADC. The digital processing part is a demodulator.
In the case of transmission, YGHF-D010A receives OQPSK-modulated anlaog signal from the
MSM6100.
The YGHF-D010A connects directly with MSM6100 using an analog baseband interface.
In YGHF-D010A, the baseband quadrature signals are upconverted to the Cellular frequency bands
and amplified in order to have enough power for radiation. Finally, the RF signal is sent out to the cell
site via the antenna.
1.2 Description of RF Part Circuit
1.2.1 RF onechip Module ( YGHF-D010A)
The RF SPM is a fully intergrated RF module for mobile handsets execpt V-TCXO. This module can
be operated in CDMA & GPS mode. This module adopted ZIF(Zero IF) chipsets that include the
VCO’s, PLLs, up/down mixers, LNA, base band LPF, and Transmitter AGC amplifier. Also additional
components are fully intergrated such as BPF, power amplifier, duplexer, swithchs. Receiver LNA
used operates 4-stepped gain control. IN addition the receiver can be controllable IP2 and automatic
DC-offset calibration. This module includes transmitter base band amplifier, up-converter, drive
amplifier. The transmitter power can be controllable greater than 85dB dynamic rages and operated
under 2.8V supply voltage except the power amplifier. The two types of filter is used for this module.
One is Tx/Rx BPFs made by CSP(Chip Scale Package) technoloty. The other is Saw Duplexer that
has high isolation and attenuation.
CHAPTER 3. Circuit Description
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