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2. SGH-E330 Circuit Description
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2-1
1. SGH-
E330
RF Circuit Description
1) RX PART
1. ASM(U103)
→
Switching Tx, Rx path for GSM900, DCS1800 by logic controlling.
2. ASM Control Logic (U103)
→
Truth Table
VC1
VC2
GSM Tx Mode
H
L
DCS Tx Mode
L
H
GSM Rx Mode
L
L
DCS Rx Mode
L
L
3. FILTER
To convert Electromagnetic Field Wave to Acoustic Wave and then pass the specific frequency band.
- GSM FILTER (F100)
→
For filtering the frequency band between 925 and 960 MHz
- DCS FILTER (F101)
→
For filtering the frequency band between 1805 and 1880 MHz.
4. VC-TCXO (OSC100)
This module generates the 26MHz reference clock to drive the logic and RF. 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.
5. 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). They are matched to 50 ohm. 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) TX PART
Baseband IQ signal fed into offset PLL, this function is included inside of U100 chip. OSC101 chip generates modulator
signal which power level is about 6.5dBm and fed into Power Amplifier(U102). The PA output power and power ramping
are well controlled by Auto Power Control circuit. We use offset PLL below table.
Modulation Spectrum
200kHz offset
30 kHz bandwidth
GSM
-35dBc
DCS
-35dBc
400kHz offset
30 kHz bandwidth
GSM
-66dBc
DCS
-65dBc
600kHz ~ 1.8MHz offset
30 kHz bandwidth
GSM
-75dBc
DCS
-68dBc
