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5. Circuit Description
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5-1
< RF Circuit Description of SGH-D807 >
1. FEM (DUF400)
==> Switching Tx, Rx path for GSM850, EGSM900, DCS1800 and PCS1900
controlled by logic.
Integration of GSM850, EGSM900, DCS1800 and PCS1900 RX SAW Filters.
To convert Electromagnetic Field Wave to Acoustic Wave and the pass the specific
frequency band.
- for filtering the frequency band 824 ~ 849 / 869 ~ 894 MHz
- for filtering the frequency band 880 ~ 915 / 925 ~ 960 MHz
- for filtering the frequency band 1710 ~ 1785 / 1805 ~ 1880 MHz
- for filtering the frequency band 1850 ~ 1910 / 1930 ~ 1990 MHz
2. FEM Control Logic
==> Truth Table
VC1
VC2
VC3
GSM850 Rx Mode
L
L
H
EGSM900 Rx Mode
L
L
L
GSM850/EGSM900 Tx Mode
L
H
L
DCS/PCS Rx Mode
L
L
L
DCS/PCS Tx Mode
H
L
L
3. VC-TCXO(TCX400)
==> To generate the 26 MHz reference clock to drive the logic and RF.
After additional process, the reference clock applies to the U401 VCXOB pin
to modulate TXIQ and demodulate RXIQ.
4. HD155154NP (U405)
==> The HD155154NP is a RF tranceiver IC for GS850, EGSM900 DCS1800
and PCS1900 QUAD band cellular systems, and incorporates EDGE tranceiver
capabillity, and integrates most of the low power silicon functions of a tranceiver.
The HD155154NP incorporates triple RF LNAs, direct conversion mixers which
are IQ demodulator, an auto offset calibrated programmable gain amplifier with
baseband filter for both IQ chains, RF architecture for the transmitter.
Moreover the HD155154NP includes power mode controller to optimize the power
consumption. These functions can operate down to 2.7V and are housed in a
48-pin DPE QFN SMD package.