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2. Circuit Description
2-1
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2-1. SGH-E750 RF Circuit Description
2-1-1. RX PART
- FEM(MODULE100)
→
Switching Tx, Rx path for GSM900, DCS1800 and PCS1900 by logic controlling.
- FEM Control Logic (MODULE100)
→
Truth Table
VC1
VC2
VC3
Tx Mode (GSM900)
H
L
L
Tx Mode (DCS1800/1900)
L
H
L(H)
Rx Mode (GSM900)
L
L
L
Rx Mode (DCS1800)
L
L
L
Rx Mode (PCS1900)
L
L
H
- VC-TCXO-2146C6(26MHz) (OSC100)
This module generates the 26MHz reference clock to drive the logic and RF.
It is turned on when the supply voltage is applied.
After buffering a reference clock of 26MHz is supplied to the other parts of the system through the transceiver pin
VCXOOUT1.
- Transceiver (U100)
This chip is a RF transceiver IC for GSM850/900, DCS1800, and PCS1900 Quad band cellular system, and incorporates
GPRS transceiver capability, and integrates most of the low power silicon functions of a transceiver.
It incorporates triple RF LNAs, direct conversion mixers which are IQ demodulator, an auto offset calibrated
programmable gain amplifier with baseband filter for IQ chains, RF synthesizer, a I/Q modulator, offset PLL, IF
synthesizer, and the circuits which are needed polar loop architecture for the transmitter.
2-1-2. TX PART
Transmitter of the transceiver is capable of GMSK and 8-PSK modulation, providing support for conventional GSM and
GPRS. The modulated signal out of the transceiver is fed into Power Amplifer Module(U101). PAM output signal is
radiated to the air through FEM(MODULE1) and antenna.