Circuit Description - Samsung SGH-E330N Service Manual

2. Circuit Description

2-1. SGH-E330N RF Circuit Description
2-1-1. RX PART
- ASM(U103) ¡ æ
Switching Tx, Rx path for GSM900, DCS1800, PCS1900 by logic controlling.
- ASM Control Logic (U103) ¡ æ
GSM Tx Mode
DCS Tx Mode
PCS Tx Mode
GSM Rx Mode
DCS Rx Mode
PCS Rx Mode
- FILTER
To convert Electromagnetic Field Wave to Acoustic Wave and then pass the specific frequency band.
- GSM FILTER (F100) ¡ æ
- DCS FILTER (F102) ¡ æ
- PCS FILTER (F101) ¡ æ
- VC-TCXO (OSC100)
This module generates the 26MHz reference clock to drive the logic and RF. After division by two a reference clock of
13MHz is supplied to the other parts of the system through the pin CLKOUT. After additional process, the reference
clock applies to the U100 Rx IQ demodulator and Tx IQ modulator. And then, the oscillator is controlled by serial data
to select channel and use fast lock mode for GPRS high class operation.
- Transceiver (U100)
The receiver front-end which amplifies the GSM, DCS aerial signal, converts the chosen channel down to a low IF signal
of 100 kHz. The first stages are symmetrical low noise amplifiers (LNAs). The LNAs are followed by an IQ down mixer.
It consists of two mixers in parallel but driven by quadrature out of phase LO signals. The In phase (I) and Quadrature
phase (Q) IF signals are low pass filtered to provide protection from high frequency offset interferes. The low IF I and Q
signals are then fed into the channel filter. The front-end low IF I and Q outputs enter the integrated bandpass channel
filter with provision for five 8 dB gain steps in front of the filter.
2-1-2. TX PART
I and Q baseband signals are applied to the IQ modulator that shifts the modulation spectrum up to the transmit IF. It is
designed for low harmonic distortion, low carrier leakage and high image rejection to keep the phase error as small as
possible.
Truth Table
VC1
H
L
H
L
L
L
For filtering the frequency band between 869 and 894 MHz
For filtering the frequency band between 1805 and 1880 MHz.
For filtering the frequency band between 1930 and 1990 MHz.
SAMSUNG Proprietary-Contents may change without notice
This Document can not be used with out Samsung' s authorization
VC2 VC3
L L
H L
L L
L L
L L
L H
2- 1