LG VX5400, Service Manual

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the power amplifier are sent to the Quintplexer.
1.4 Description of Frequency Synthesizer Circuit
1.4.1 Voltage Control Temperature Compensation Crystal Oscillator (VCTCXO, X100)
The temperature variation of mobile phone can be compensated by VCTCXO. The reference frequency of a
mobile phone is 19.2 MHz. The receiver frequency tuning signals called TRK_LO_ADJ from MSM as 0.5
V~2.5 V DC via R and C filter in order to generate the reference frequency of 19.2 MHz and input it into the
frequency synthesizer. Frequency stability depending on temperature is
±
2.0 ppm.
1.4.2 Voltage Controlled Oscillator (VCO, U110)
The external VCO signal is processed by the LO generation and distribution circuits in RFR6000 to create the
PCS and Cellular quadrature downconverter’s LO signals. Likewise, the internal VCO signal of RFR6000 is
processed to create the GPS quadrature downconverter’s LO signal. In all cases, the LO signals applied at the
mixer ports are at the frequency different than the VCO frequency. This assures that the VCO frequency is
different than the RF frequency, an important consideration for Zero-IF processing. The VCO frequency used
are 1715.56~1768.89 MHz for PCS and 1738.08~1787.94 MHz for cellular.
2. Digital/Voice Processing Part
2.1 Overview
The digital/voice processing part processes the user's commands and processes all the digital and voice signal
processing in order to operate in the phone. The digital/voice processing part is made up of a keypad/LCD,
receptacle part, voice processing part, mobile station modem part, memory part, and power supply part.
2.2 Configuration
2.2.1 Keypad/LCD and Receptacle Part
This is used to transmit keypad signals to MSM6100. It is made up of a keypad backlight part that illuminates
the keypad, LCD part that displays the operation status onto the screen, and a receptacle that receives and sends
out voice and data with external sources.
LGE Internal Use Only Copyright@2007 LG Electronics. Inc. All right reserved.
-28-
Only for training and serving purposes
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