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1、ADC与DAC 衡量指标:衡量指标:静态指标:DNL,INL;动态指标:SNR,SINAD,THD,ENOB,IMD,etc.动态指标(1)静态指标反映的特点有限,主要是慢速变化特性,也称之为DC传输特性,对于高速D/A,A/D来说,更需要AC传输特性来表征,反映不同频率信号的响应。主要反映了D/A,A/D器件的高速工作情况下的性能,诸如,VEDIODAC,TXDAC,TXADC等,动态指标(2)SNR:SignaltoNoiseRatioSINAD:SignaltoNoiseAndDistortionRatioTHD:TotalHarmonicDistortionENOB:Effective
2、NumberOfBitsSFDR:Spurious-FreeDynamicRangeTwo-toneIMD.FrequencyDomainAnalysisFt(M)FrequencyMagnitudeSH2H3H4H5NoiseHarmonicsFundamentalSignalSpurious动态特性的测试方法(1)对于DAC来说,相对简单一些,通过编程产生单频信号,然后将输出的信号发送到频谱分析仪。动态特性的测试方法(2)DUT(ADC)AnalogSourceDigitalCaptureDataProcessing(FFT)SinusoidalWaveFrequencySpectrumn
3、bitsClockSourceRXADC测试环境要求(1)Inputsignalrequests:1:Qualityofsignal:SNR,THD.2:Amplitude,frequencyandcommonvoltageofsignal.3:fourorthogonaldifferentialsignals;RXADC测试环境要求(2)Howtoselectsamplenumbers-coherentsamplingFin/Fsample=Ncycle/Nrecord,Fin:PeriodicinputsignalFsample:SamplingfrequencyoftheADCNcycl
4、e:IntegernumberofcycleswithinthesamplingwindowNrecord:NumberofdatapointsinthesamplingwindoworFFTCoherentsamplingUncoherentsamplingWindowingRXADC测试环境要求(3)在rxadc的测试中,Fin=Ncycle*Fsample/NrecordFin (kHz)Fsamp (kHz)NrecordNcycle10.3819270.8336002340.1736270.8336008960.0347270.833600133RXADC测试环境要求(4)Spect
5、ralleakagesamplesequencenotmeetscoherentsamplingWindowingminimizesspectralleakageWindowfunctionWindowtypes:Rectangular,Hamming,Hanning,BlackmanHowtoselectwindowfunction:1:-3dBbandwidth;2:-6dBbandwidth3:maximumside-lobelevel4:side-loberoll-offrateBlackmanwindows-singletonetestWindowsfunctionWindowsfu
6、nctionCalculation(1):FFTPs=sumPf(m-k):1:Pf(m+k);Pdc=sumPf(1:k);Ph=sumPh(2:n);Ph(i)=sumPh(i-1:i+1);Pn=sum(Pf)-Ps-PdcPh;Signalbin的选择:Calculation(2):FFTS/N=10*log(Ps/Pn);SINAD=10*logPs/(Pn+Ph);THD=10*log(Ph/Ps);SFDR=10*logPs/Pmax.spuriousLevel;ENOB=(SINAD-1.763)/6.02SignalbinS/N=10*log(Ps/Pn);=S/N=10*logPs(1+)/Pn(1-10%)=10*log10/9+log(Ps/Pn)=0.46+S/NI/QmatchAnidealsinusoidalI/Qsignalpair:y(t)=Aexp(i(t+)=Acos(t+)+iAsin(t+)I/QmismatchAmplitudemismatchandphasemismatch:y(t)=Acos(t+)+iAsin(t+)=0.5(1+exp(i)Aexp(i(t+)+0.5(1-exp(-i)Aexp(-i(t+)I/QmismatchcalculationAmplitude=20log(Iamp/Qamp);