Lg Electronics LGC800W ユーザーズマニュアル

The RF transceiver (transmitter and receiver) employs Super-Heterodyne system. The frequency ranges of

transmitter and receiver are 824.640~848.370 MHz and 869.640~893.370 MHz respectively. The block diagram

of this mobile phone is shown in figure 1.

RF signals received from the antenna are fed into the mixer through the duplexer. Mixer converts RF signals into

intermediate frequency (IF) signals by mixing RF signals with signals from local Oscillator (VCO). IF signals are

sent to AGC (Auto Gain Controller) contained in the IFR (Internediate Frequency Receiver) through bandpass

filter (BPF). The signals are converted to baseband signals and finally sent to MSM.

In the case of transmission, IFT (Internediate Frequency Transmitter) receives modulated digital signals from the

MSM and creates analog baseband signals using the digital/analog converter (DAC, D/A Converter). Baseband

signals are changed into IF siganls, and these signals are fed into Mixer after adjusting the gain with AGC in IFT.

If signals are converted into RF signals in the Mixer, and the gain of  signals are adjusted once more by RF

AGC. RF signals are amplified by drive anmplifier and, thereafter, fed into Power Amplifier. Amplified signals

are sent out to the cell site via the antenna after going through the isolator and duplexer.

Block Diagram of RF Tansmitter and Receiver Circuit

 CHAPTER 3. Circuit Description

RX, PLL

IFT3000

IFR3000

M

S

M

3

0

0

0

VCO/PLL

DPX

ANT

CP

PAM

CODEC
TX

IFT/IFR

ISO

PA