微弱信號(hào)檢測(cè)技術(shù)

1、dttf2)(222| )(|1limTTdttfTT dttxTTTx01lim dttxTTTx0221lim dttxTTxTx2021lim222xxxniinxttttT121TTxxtxxPxTlim)(xxxtxxPxpx)(lim)(0 22221axexp dttxtxTRTTTxx221lim dttytxTRTTTxy22*1lim 22221lim0 xTxxdttxTRTT deRfSfjxxxx2 dfefSRfjxxxx2 deRfSfjxyxy2 dfefSRfjxyxy2 22)()(1lim022TTdffsdttxTRxTxx dffGGf001NS)(信

2、號(hào)中含有的噪聲功率信號(hào)功率信噪比SNRiiooNSNS)S(輸入端信噪比輸出端信噪比信噪改善比NIR熱噪聲熱噪聲功率譜密度在很寬的功率譜密度在很寬的頻率范圍內(nèi)恒定，為頻率范圍內(nèi)恒定，為白噪聲白噪聲散粒噪聲散粒噪聲低頻噪聲低頻噪聲頻率增加，功率譜減頻率增加，功率譜減小。由于功率譜密度小。由于功率譜密度與頻率有關(guān)，所以也與頻率有關(guān)，所以也叫色噪聲叫色噪聲接觸噪聲接觸噪聲fkTREt4fqIIdcsh2q: 電子電荷，電子電荷，q=1.610-19CIdc: 平均直流電流平均直流電流(A)f: 系統(tǒng)帶寬系統(tǒng)帶寬(Hz)dcdcshIqIfI101066. 52 fKfStE lhffffEEEffK

3、dffKdffSRhlhltttln)0(2fKIfIdcf21222122xxxxx22212xxx2212)(xxx2111RREI2122RREI221222122212)(RREEIII I1R2R1E2EdttxtxdttxtxRRxx)()( )()()()( )()(1lim)()(22TTdttxtxTRRTxx )()(1lim)(22TTdttytxTRTxy )()(1lim)(22TTdttxtyTRTyxdttxtydttytxRxy)()( )()()(dttytxdttxtyRyx)()( )()()( yxxyRR *yxxyRR txtxsin0 )(sin)

4、sin(1lim)(2200TTdttxtxTRTx)cos(2 0)cos(21lim 2020 xTxTT )22cos(21lim)cos(21lim )22cos()cos(21lim 222222202020TTTTTTdttxTdtxTdttxTTTTl見(jiàn)見(jiàn))(R0l見(jiàn)見(jiàn) tntStfiii)(tfi)(R)(R)(R)(R )()()()( )()()()(1lim )()()()(1lim )()(1lim)(nnnssnss222222222222TTTTTTTTTTTTdttntndttstndttntsdttstsTdttntstntsTdttftfTRiiiiiiiii

5、iiiii0)()(nssnRR)()(ssRR0)(limnnR txtxsin0)()()(nnxxRRRcos21)(20 xR tntStf11 tStf22)(R)(R )()()(1lim )()(1lim)(2212222s212112nssTTTTTTdttstntsTdttftfTR0)(2nsR)()(2112ssRR窄窄帶帶濾濾波波放放大大)(1tU)(2tU)(1tUs)(tUO輸入信號(hào)參考信號(hào)鎖定放大器原理 )cos(2 )()cos( )()cos(2 )()(1)(212212121210220UUKdtttUUTKdttUtUKTtUiiiOsvTsvTsvsv

6、K21)sin()()sin()(22221111tUtUtUtUss ：脈沖寬度：信號(hào)周期式中其余，20msT100T 0 2nT2nT 1000msTTtS已知：混有噪聲已知：混有噪聲n(t)的脈沖信號(hào)的脈沖信號(hào)f(t)，f(t)=s(t)+n(t)，其中其中n(t)為幅值在為幅值在-1,1區(qū)間的白噪聲。區(qū)間的白噪聲。計(jì)算自相關(guān)檢測(cè)計(jì)算自相關(guān)檢測(cè)輸出信號(hào)，并作圖。采樣點(diǎn)數(shù)輸出信號(hào)，并作圖。采樣點(diǎn)數(shù)2048，采頻自定。，采頻自定。 tptftfsTtTtTttT 5t tt tT: 被取樣信號(hào)周期t:取樣步進(jìn)值UiUotTNntfi1)(TtTNtntTNntffi加長(zhǎng)倍數(shù))()()(tntftfs)()()(iTtniTtfiTtfkksk)()(1iTtmfiTtfksmiks)()()()(2121tnmtnmiTtniTtnmikmik)(tnininksksoutmoutmSNRmNSmtni