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2. Circuit Description
2-1
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1. SGH-X480, SGH-X480C,SGH-X488 RFCircuitDescription
1)RX PART
1.ASM(F900)→SwitchingTx,RxpathforGSM900,DCS1800 and PCS1900 bylogic controlling.
2.ASMControlLogicTruthTable
VC1VC2VC3
Tx(GSM900)HL L
Tx(DCS1800/PCS1900)LHL
Rx(GSM900)LLL
Rx(DCS1800)LLL
Rx(PCS1900)L L H
3.SawFILTER
ToconvertElectromagneticFieldWavetoAcousticWave and then pass thespecificfrequency band.
-GSMFILTER(F800)→For filtering thefrequency band between 925 and 960 MHz.
-DCS FILTER(F800)→For filtering thefrequency band between 1805 and 1880 MHz
-PCS FILTER(F801)→For filtering thefrequency band between 1930 and 1990 MHz.
4.Crystal(U802)
To generatethe26MHzreference clockto drivethelogic and RF.
Afteradditionalprocess,thereference clockappliestotheU801 RxIQdemodulatorand TxIQmodulator.
Theoscillator forRXIQdemodulatorand Txmodulatorare controlled by serialdatatoselectchanneland usefast lock
modeforGPRShigh class operation.
5.Si4210 (U801)
Thereceivesection integratesfourdifferential-input lownoise amplifiersLNAs supporting theGSM850,EGSM900,
DCS1800 and PCS1900 bands.TheLNA inputsarematchedtothe150 ohmbalanced-outputSAWfiltersthrough externa
LCmatching network.
AquadratureImage-rejectmixerdownconvertstheRFsignal toa200 KHzintermediatefrequency(IF).Themixeroutput is
amplifiedwithananalog programmablegainamplifier(PGA)that iscontrolledwiththeAGAIN.ThequadratureIF? ?
isdigitizedwith high resolution analog-to-digitalconverts(ADC).
TheADCoutput isdownconvertedto baseband withadigitalquadratureLOsignal.Digitaldecimation and FIRfilters
performdigitalfiltering and removeADCquantization noise,blockersand reference interferers.
After filtering,thedigitaloutput is scaledwithadigitalPGA,whichiscontrolledwiththeDGAIN.DACsdrive a
differentialIand Qanalog signalontotheBIP,BIN,BQPand BQN pinstointerface tostandardanalog-inputbaseband
ICs.
