基于单片机的数字时钟设计--外文翻译(19)

Abstract Virtually complete charge transfer can be achieved with charge coupleddevices(CCDs)intheburiedchannelconfigurationbecausetheburiedchannelCCDintroduces no transfer noise. However, conventional charge detectors incorporatedinto CCDs have a comparably large noise, which consists of thermal noise and 1/fnoisefromMOS transistorin theoutputchargedetectors.

10Low-NoiseElectronicImagingwithDouble-GateFETs

Fig.10.23Inputpulsesand

outputsignalwaveformsof

detector.(a)Saturationsignal

withoutfeedbackloop.(b)

Compressedsignalwith

negativefeedback.(c)

Saturationsignalwith

negativefeedback

loop237

cycleofthehorizontalCCDdrivingpulse,respectively.Withthecapacitance-coupledfeedbackloop,thesaturationchargelevelisincreasedbyafactorof5,andthedynamicrangeisimprovedto94dB,maintainingtheeffectivereadoutnoiseof1.0electronrms.

ThecharacteristicsoftheimagesensorwiththenewdetectorareshowninTable10.1.TheverylowdarkcurrentisrealizedbytheburiedphotodiodestructureandthepinnedoperationoftheV-CCD.Inthepinnedoperation,thesurfaceemissionunderthetransferelectrodes,onwhichthelow-levelvoltageoftransferpulseisapplied,issuppressedbecauseholesareaccumulatedthere.

10.3.4SignalProcessing

Theoutputsignalincludesthelarge1=fnoisegeneratedbytheMOStransistorsoftheon-chipdetector.Figure10.25showsthenoisespectrumoftheon-chipdetectorwithoutthefeedbackloop.The1=fnoisegeneratesaveryconspicuousstreaknoiseinthereproducedimageinspiteofitssmallnoisepower.The1=fnoiseshouldthereforebesuppressedtorealizealow-noiseimagesensor.Anoisereductionsignalprocessingtechniquecalledalternategaininversion(AGI)isproposedtosolvetheproblem.Thisprocessingisabletosuppressnotonlythe1=fnoisebutalsothekTC

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