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 Ha

2、rmonic Distortion 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)AnalogSourceDigitalCaptureDa

3、taProcessing(FFT)Sinusoidal 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 /

4、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 FFTCoherent samplingUncoherent samplingWindowing RXADC 测试环境要求（3） 在rxadc的测试中， Fin= Ncy

5、cle * Fsample / Nrecord Fin (kHz)Fsamp (kHz) NrecordNcycle10.3819270.83360023 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, Blac

6、kman How 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 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);

7、 Pn = sum(Pf) - Ps- Pdc Ph; Signal bin 的选择：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)/ 6.02Signal bin S/N = 10* log(Ps/Pn);= S/N = 10* logPs(1+)/Pn(1-10%) = 10*log10/9+log(Ps/Pn) = 0.46 +

8、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);