LG VX5400, Service Manual

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CHAPTER 3. Circuit Description
1. RF Transmit/Receive Part
1.1 Overview
The Tx and Rx part employs the Direct-Conversion system. The Tx and Rx frequencies are respectively
824.04~848.97 and 869.04~893.97 for cellular and 1850~1910 and 1930~1990 for PCS. The block diagram is
shown in [Figure 1-1]. RF signals received through the antenna are seperated by the Quintplexer.
RF Signal fed into the low noise amplifier (LNA) through the Quintplexer. Then, they are fed into RFR6000. In
RFR6000, 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, RFT6100 receives OQPSK-modulated anlaog signal from the MSM6100.
The RFT6100 connects directly with MSM6100 using an analog baseband interface. In RFT6100, the baseband
quadrature signals are upconverted to the Cellular or PCS frequency bands and amplified to provide signal drive
capability to the power amp.
After that, the RF signal is amplified by the Power Amp in order to have enough power for radiation. Finally,
the RF signal is sent out to the cell site via the antenna after going through the Quintplexer.
[Figure 1-1] Block Diagram Of VX5400
Only for training and serving purposes
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