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2. SGH-P400 Circuit Description
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1. SGH-P400 RF Circuit Description
1) RX PART
1. ASM(U1005)
ð
510
Switching Tx, Rx path for GSM900, DCS1800 and PCS1900 by logic
controlling.
2. ASM Control Logic (U701, U702, U703)
ð
Truth Table
VC1
VC2
VC3
GSM Tx Mode
H
L
L
DCS /PCS Tx Mode
L
H
L
PCS Rx Mode
L
L
H
GSM / DCS Rx Mode
L
L
L
3. FILTER
To convert Electromagnetic Field Wave to Acoustic Wave and then pass the
specific frequency band.
- GSM FILTER (C1003,C1004,L1001)
ð
For filtering the frequency band between 925 ~ 960 MHz
- DCS FILTER (C1005,C1006,L1002)
ð
For filtering the frequency band 1805 and 1880 MHz.
- PCS SAW FILTER (F1003,C1009,C1010,L1006)
ð
For filtering the frequency band
between 1930 and 1990 MHz
4. TC-VCXO (OSC801)
To generate the 13MHz reference clock to drive the logic and RF.
After additional process, the reference clock is applied to the U900 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.