微弱信号检测技术-课件.ppt

1、-2-3-4-5-6-7dttf2)(222|)(|1limTTdttfTT-8 dttxTTTx01lim dttxTTTx0221lim dttxTTxTx2021lim222xxxniinxttttT121TTxxtxxPxTlim)(xxxtxxPxpx)(lim)(0-10 22221axexp dttxtxTRTTTxx221lim dttytxTRTTTxy22*1lim 22221lim0 xTxxdttxTRTT deRfSfjxxxx2 dfefSRfjxxxx2 deRfSfjxyxy2 dfefSRfjxyxy2 22)()(1lim022TTdffsdttxTRxTx

2、x-13 dffGGf001-14NS)(信号中含有的噪声功率信号功率信噪比SNRiiooNSNS)S(输入端信噪比输出端信噪比信噪改善比NIR-16热噪声热噪声功率谱密度在很宽的功率谱密度在很宽的频率范围内恒定，为频率范围内恒定，为白噪声白噪声散粒噪声散粒噪声低频噪声低频噪声频率增加，功率谱减频率增加，功率谱减小。由于功率谱密度小。由于功率谱密度与频率有关，所以也与频率有关，所以也叫色噪声叫色噪声接触噪声接触噪声fkTREt4-18-19fqIIdcsh2q:电子电荷，电子电荷，q=1.610-19CIdc:平均直流电流平均直流电流(A)f:系统带宽系统带宽(Hz)dcdcshIqIfI10

3、1066.52 fKfStE lhffffEEEffKdffKdffSRhlhltttln)0(2fKIfIdcf-2321222122xxxxx22212xxx2212)(xxx-242111RREI2122RREI221222122212)(RREEIII I1R2R1E2E-25-26-29dttxtxdttxtxRRxx)()()()()()()()(1lim)()(22TTdttxtxTRRTxx)()(1lim)(22TTdttytxTRTxy)()(1lim)(22TTdttxtyTRTyxdttxtydttytxRxy)()()()()(dttytxdttxtyRyx)()()

4、()()(-31 yxxyRR*yxxyRR txtxsin0 )(sin)sin(1lim)(2200TTdttxtxTRTx)cos(2 0)cos(21lim 2020 xTxTT)22cos(21lim)cos(21lim )22cos()cos(21lim 222222202020TTTTTTdttxTdtxTdttxTTTTl见见-33)(R0l见见 tntStfiii)(tfi)(R)(R)(R)(R )()()()()()()()(1lim )()()()(1lim )()(1lim)(nnnssnss222222222222TTTTTTTTTTTTdttntndttstndt

5、tntsdttstsTdttntstntsTdttftfTRiiiiiiiiiiiiii0)()(nssnRR)()(ssRR0)(limnnR txtxsin0)()()(nnxxRRRcos21)(20 xR-37-38 tntStf11 tStf22-39)(R)(R )()()(1lim )()(1lim)(2212222s212112nssTTTTTTdttstntsTdttftfTR0)(2nsR)()(2112ssRR-40窄窄带带滤滤波波放放大大)(1tU)(2tU)(1tUs)(tUO输入信号参考信号锁定放大器原理 )cos(2 )()cos()()cos(2 )()(1)(

6、212212121210220UUKdtttUUTKdttUtUKTtUiiiOsvTsvTsvsvK21)sin()()sin()(22221111tUtUtUtUss-42-43-44-45-46：脉冲宽度：信号周期式中其余，20msT100T 0 2nT2nT 1000msTTtS已知：混有噪声已知：混有噪声n(t)的脉冲信号的脉冲信号f(t)，f(t)=s(t)+n(t)，其中其中n(t)为幅值在为幅值在-1,1区间的白噪声。区间的白噪声。计算自相关检测计算自相关检测输出信号，并作图。采样点数输出信号，并作图。采样点数2048，采频自定。，采频自定。-49-50-51-53 tptftfsTtTtTttT 5t tt tT:被取样信号周期t:取样步进值UiUotTNntfi1)(TtTNtntTNntffi加长倍数-60-63)()()(tntftfs)()()(iTtniTtfiTtfkksk)()(1iTtmfiTtfksmiks)()()()(2121tnmtnmiTtniTtnmikmik)(tnininksksoutmoutmSNRmNSmtniTtfmtnmiTtmfNSSNR )()()()(|mSNRSNRSNIRinoutmm|tTsmnSNIR 为信号最高频率，mmgffT4431.0-70smnSNIR-7236max1010 SNIR-77