ADC与DAC动态性能测试课件.ppt

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，VEDIO DAC,TXDAC，TX ADC等，动态指标（2）SNR:Signal to Noise Ratio SINAD:Signal to Noise And Distortion Ratio THD:Total Harmonic Distortion

2、 ENOB:Effective Number Of Bits SFDR:Spurious-Free Dynamic Range Two-tone IMD.Frequency Domain Analysis Ft(M)FrequencyMagnitudeSH2 H3 H4 H5NoiseHarmonicsFundamentalSignalSpurious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)Sin

3、usoidal WaveFrequency Spectrum nbitsClockSourceRXADC 测试环境要求（1）Input signal requests：1：Quality of signal：SNR,THD.2：Amplitude,frequency and common voltage of signal.3：four orthogonal differential signals；RXADC 测试环境要求（2）How to select sample numbers-coherent sampling Fin/Fsample=Ncycle/Nrecord,Fin:Perio

4、dic input signal Fsample:Sampling frequency of the ADC Ncycle:Integer number of cycles within the sampling window Nrecord:Number of data points in the sampling window or FFTCoherent samplingUncoherent samplingWindowing RXADC 测试环境要求（3）在rxadc的测试中，Fin=Ncycle*Fsample/Nrecord Fin(kHz)Fsamp(kHz)NrecordNcy

5、cle10.3819270.83360023 40.1736 270.83360089 60.0347 270.833600133 RXADC 测试环境要求（4）Spectral leakage sample sequence not meets coherent sampling Windowing minimizes spectral leakageWindow function Window types:Rectangular,Hamming,Hanning,Blackman How to select window function:1:-3dB bandwidth;2:-6dB ba

6、ndwidth 3:maximum side-lobe level 4:side-lobe roll-off rate Blackman windows-single tone testWindows functionWindows functionCalculation(1):FFT Ps =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-Pdc Ph;Signal bin 的选择：Calculation(2):FFT S/N =10*log(Ps/Pn);SINA

7、D=10*logPs/(Pn+Ph);THD =10*log(Ph/Ps);SFDR =10*logPs/Pmax.spurious Level；ENOB =(SINAD-1.763)/6.02Signal bin S/N=10*log(Ps/Pn);=S/N =10*logPs(1+)/Pn(1-10%)=10*log10/9+log(Ps/Pn)=0.46+S/N I/Q match An ideal sinusoidal I/Q signal pair:y(t)=A exp(i(t+)=A cos(t+)+i A sin(t+)I/Q mismatch Amplitude mismatch and phase mismatch :y(t)=A cos(t+)+i A sin(t+)=0.5(1+exp(i)A exp(i(t+)+0.5(1-exp(-i)A exp(-i(t+)I/Q mismatch calculation Amplitude =20log(Iamp/Qamp);