ADC与DAC 动态性能测试.ppt

1、A,1,ADC与DAC,衡量指标： 静态指标：DNL, INL; 动态指标：SNR, SINAD, THD ,ENOB, IMD,etc.,A,2,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，,A,3,动态指标（2）,SNR: Signal to Noise Ratio SINAD: Signal to Noise And Distortion Ratio THD:

2、Total Harmonic Distortion ENOB: Effective Number Of Bits SFDR: Spurious-Free Dynamic Range Two-tone IMD.,A,4,Frequency Domain Analysis,Ft (M),Frequency,Magnitude,S,H2 H3 H4 H5,Noise,Harmonics,Fundamental Signal,Spurious,A,5,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。,A,6,动态特性的测试方法（2）,DU

3、T (ADC),Analog Source,Digital Capture,Data Processing (FFT),Sinusoidal Wave,Frequency Spectrum,n bits,Clock Source,A,7,RXADC 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；,A,8,RXADC 测试环境要求（

4、2）,How to select sample numbers -coherent sampling Fin / Fsample = Ncycle / Nrecord, Fin : Periodic 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 FFT,A,9,Coherent sampling,A,

5、10,Uncoherent sampling,A,11,Windowing,A,12,RXADC 测试环境要求（3）,在rxadc的测试中， Fin= Ncycle * Fsample / Nrecord,A,13,RXADC 测试环境要求（4）,Spectral leakage sample sequence not meets coherent sampling Windowing minimizes spectral leakage,A,14,Window function,Window types: Rectangular, Hamming , Hanning, Blackman Ho

6、w to select window function: 1: -3dB bandwidth ; 2: -6dB bandwidth 3: maximum side-lobe level 4: side-lobe roll-off rate Blackman windows -single tone test,A,15,Windows function,A,16,Windows function,A,17,Calculation (1): FFT,Ps = sumPf(m-k):1:Pf(m+k); Pdc = sumPf(1:k); Ph = sumPh(2:n) ; Ph(i)= sumP

7、h(i-1:i+1); Pn = sum(Pf) - Ps- Pdc Ph; Signal bin 的选择：,A,18,Calculation (2): FFT,S/N = 10* log(Ps/Pn); SINAD = 10* logPs/(Pn+Ph); THD = 10* log(Ph/Ps); SFDR = 10* logPs / Pmax.spurious Level； ENOB = (SINAD - 1.763)/ 6.02,A,19,Signal 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,A,20,I/Q match,An ideal sinusoidal I/Q signal pair : y(t) = A exp(i(t + ) = A cos(t + ) + i A sin(t + ),A,21,I/Q mismatch,Amplitude mismatch and phase mismatch : y(t) = A cos(t + ) + i A sin(t + + ) = 0.5