Avago ALM-1912 GPS前端接收方案

AvagoALM-1912GPS前端接收方案Avago公司的ALM-1912是GPS前端模块,包括有GPSFBAR滤波器和高增益低噪音放大器(LNA).ALM-1912具有非常低的噪音和极好Cell/PCS/WLAN频带抑制,在1.575GHz,Vdd=2.7V和Idd=6mA时,增益为19.3dB,NF=1.62dB,IIP3=+1.5dBm,IP1dB=-8dBm,主要用作GPS前端模块.本文介绍了ALM-1912主要特性和指标,应用电路,演示和应用电路元件表以及演示和应用电路框图与S参数测量参考平面.

AvagoTechnologies’ALM-1912isaGPSfront-endmodulethatcombinesaGPSFBARfilterwithhigh-gainlow-noiseamplifier(LNA).TheLNAusesAvagoTechnologies’proprietaryGaAsEnhancement-modepHEMTprocesstoachievehighgainwithverylownoisefigureandhighlinearity.Noisefiguredistributionisverytightlycontrolled.

ACMOS-compatibleshutdownpinisincludedeitherforturningtheLNAon/offorforcurrentadjustment.ThefilteruseAvagoTechnologies’leading-edgeFBARfilterforlowGPSbandinsertionlossandexceptionalrejectionatCellular,PCSandWLANbandfrequencies.

Thelownoisefigureandhighgain,coupledwithlowcurrentconsumptionmakeitsuitableforuseincriticallow-powerGPSapplicationsorduringlow-batterysituations.

ALM-1912主要特性:

VeryLowNoiseFigure

ExceptionalCell/PCS/WLAN-Bandrejection

Lowexternalcomponentcount

Fully-matchedatRFinputandRFoutput

Shutdowncurrent:<1uA

CMOScompatibleshutdownpin(SD)

ESD:>3kVatRFinpin

2.9x2.0x0.95mmsize

Adjustablebiascurrentviasingleexternalresistor/voltage

Lead-freeandHalogenfree

Specifications(Typicalperformance@25℃)

At1.575GHz,Vdd=2.7V,Idd=6mA

Gain=19.3dB

NF=1.62dB

IIP3=+1.5dBm

IP1dB=-8dBm

S11=-9.5dB

S22=-13.5dB

Cell-BandRejection:>57dBc

PCS-BandRejection:>53dBc

WLAN-BandRejection:>52dBc

ALM-1912应用:

GPSFront-endModule

图1.ALM-1912应用电路

图2.ALM-1912演示和应用电路元件表

图3.ALM-1912演示和应用电路框图

Notes

ThemoduleisfullymatchedattheinputandoutputRFpins.Boththesepinsalsohavebuilt-incouplingandDC-blockingcapacitors.Bestnoiseperformanceisobtainedusinghigh-Qwirewoundinductors.Thiscircuitdemonstratesthatlownoisefiguresareobtainablewithstandard0402chipinductors.

C2andL2formamatchingnetworkthataffectsthefrequencyresponseandlinearityoftheLNA,thesecanbetunedtooptimizegainandreturnloss.

L1andR1isolatesthedemoboardfromexternaldisturbancesduringmeasurement.Itisnotneededinactualapplication.Likewise,C1andC3mitigatetheeffectofexternalnoisepickupontheVddandVsdlinesrespectively.Thesecomponentsarenotrequiredinactualoperation.

BiascontrolisachievedbyeithervaryingtheVsdvoltagewith/withoutR2,orfixingtheVsdvoltagetoVddandadjustingR2forthedesiredcurrent.

R2=4.7Kohmwillresult6mAwhenVdd=Vsd=2.7V.R2=2.7Kohmfor4mAw