Sharp SD-AT1000W Spécifications télécharger pdf (Page 105)

Maxiva UAX

October 17, 2013

3‐37

888‐2693‐004 WARNING:Disconnectprimarypower priortoservicing.

Note

If this limit is too low, in-band and out-of-band intermodulation products will increase due to the signal

clipping. If the limit is too high, the RTAC nonlinear corrector performance may be degraded due to high

peak stretch. Also high peaks could cause nuisance overdrive faults in some transmitter systems.

STEP 1 Inthe’RTAC’SetupScreen1,onleftFigure3‐34onpage3‐33,setRTACLinear

andNon‐Linearfunctionsto’Bypass’.

STEP 2 TheRFoutputshouldbesettothelevelrequiredfortransmitteroperation.

STEP 3 IntheRTAC‘PeakReduction’subwindowofRTACSetupScreen3,onleft

Figure3‐35onpage3‐35,ve

rifythattheNon‐LinearRangeandMaxCrest

Factorindica

torsdisplay‘Enabled’.

STEP 4 IntheRTAC’PeakReduction’subwindowstartwiththeNon‐LinearRangeat

thedefaultvalue.SeeTable3‐25onpage3‐36.

STEP 5 WithbothRTACcorrectorsbypassed,theexciterRFoutputadjacentchannel

noiseshouldbe50dBto55dBbelowtheinbandsignallevel.

AstheNonlinear(Correction)Rangevalueisreduced,thefirstsignofadjacentchannelintermodulationproduct

increasewillbeverysubtle,withthefirstsignoftenbeingincreasednoiseintheareajustoutsidethein‐band

channelbandpass

TheRT

ACnonlinearcorrectoroccasionallygeneratespeaksashighas18dBabovetheaverageoutputlevel.

Therefore,thepeakpoweroutputfromtheexcitermustbelimitedinordertoprotectthefollowingamplifierstages.

STEP 6

Endofprocedure.

3.7.5.2 MaxCrestFactorSetup

TheMax(Maximum)CrestFactorsettinglimitsthepeaktoaverageRFoutputpowerratio(7.8to17.8dB)atthe

outputoftheex citer.ThisdirectlylimitsthetransmitterRFoutputpeaktoaveragepowerratio.TheCrestFactorof

thetransmittedsignalisdeterminedbythissettingandbythepeakc

ompressionoftheamplifiersystem.

• Ifthelimitissettoolow,clippingwillgenerateout‐of‐bandintermodulationproductsintheex citer’soutput

andmayaffecttheperformanceoftheRTACnon‐linearcorrection.

• Ifsettoohigh,itcouldallownuisanceover drivetripsinsometransmittermodels,becausethehighampli‐

tudepe

akscouldoverdrivethePAmodules.

Nuisanceov

erdrivetripscanbeavoidedbysettingtheMaxCrestFactorparametersectionoftheRTACPeak

ReductionsubwindowinRTACSetupScreen3,onleftFigure3‐35onpa

ge3‐35.

Nuisanceover

drivetripswilltypicallyoccurwithin30minutesto1houraftertransmitteroperationwithRTACisfirst

started.Ifthishappens,performthefollowing:

STEP 1

Thissetupisperformedwiththetransmitteroperatingatfullpowerand

RTACLinearandNon‐LinearfunctionssettoAdapt.

STEP 2 StartwiththeMaxCrestFactoratthedefaultvalue.SeeTable3‐25on

page3‐36.

STEP 3 ReducetheMaxCrestFactorby0.2dB.

STEP 4 Waitforonehourtoseeiffurtheroverdrivetripsoccur.Iftheydo,reduceby

another0.2dB.

STEP 5 Repeatsteps3&4untiloverdrivetripscease.

STEP 6 Excessivereductionwilleffectthelinearitycorrectionofthetransmitter.

AfterMaxCrestFactorhasbeenadjusted,observetheadjacentchannel

responsetoensurethatitstillexceedsthetransmitteroutputsignalmask

requirements.

STEP 7 Endofprocedure.

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