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2 . S G H - X 1 0 0
C i r c u i t
X100 RF Circuit De s cription
1 . SGH -
1) RX PART
1. ASM(U100) ¡æ Switching Tx, Rx path for GSM900, DCS1800 by logic controlling.
2. ASM Control Logic (U104, U106) ¡æ Truth Table
GSM Tx Mode
DCS Tx Mode
GSM Rx Mode
DCS Rx Mode
3. FILTER
To convert Electromagnetic Field Wave to Acoustic Wave and then pass the specific frequency band.
- GSM FILTER (F101) ¡æ For filtering the frequency band between 925 ~ 960 MHz
- DCS FILTER (F102) ¡æ For filtering the frequency band 1805 and 1880 MHz.
4. VC-TCXO (OSC101)
To generate the 26MHz reference clock to drive the logic and RF. After additional process, the reference clock applies to
the U103 Rx IQ demodulator and Tx IQ modulator. The oscillator for RX IQ demodulator and Tx modulator are
controlled by serial data to select channel and use fast lock mode for GPRS high class operation.
5. Transceiver (U103)
The receiver front-end converts the aerial RF signal from EGSM, DCS bands down to a low intermediate frequency (IF)
of 100 kHz. The first stages are symmetrical low noise amplifiers (LNAs). They are matched to 50 ohm. The LNAs are
followed by an I, Q 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 U103 chip. OSC100 chip generates modulator
signal which power level is about 6.5dBm and fed into Power Amplifier(U101). The PA output power and power ramping
are well controlled by Auto Power Control circuit. We use offset PLL below
Modulation Spectrum
D e s c r i p t i o n
VC1
H
L
L
L
200kHz offset
30 kHz bandwidth
400kHz offset
30 kHz bandwidth
600kHz ~ 1.8MHz offset
30 kHz bandwidth
SAMSUNG Proprietary-Contents may change without notice
This Document can not be used without Samsung's authorization
VC2
L
H
L
L
GSM
DCS
GSM
DCS
GSM
DCS
2- 1
-35dBc
-35dBc
-66dBc
-65dBc
-75dBc
-68dBc
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