ADC与DAC 衡量指标： 静态指标：DNL, INL; 动态指标：SNR, SINAD, THD ,ENOB, IMD,etc.

Presentation on theme: "ADC与DAC 衡量指标： 静态指标：DNL, INL; 动态指标：SNR, SINAD, THD ,ENOB, IMD,etc."— Presentation transcript:

1 ADC与DAC 衡量指标： 静态指标：DNL, INL; 动态指标：SNR, SINAD, THD ,ENOB, IMD,etc.

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，

3 动态指标（2） SNR: Signal to Noise Ratio
SINAD: Signal to Noise And Distortion Ratio THD: Total Harmonic Distortion ENOB: Effective Number Of Bits SFDR: Spurious-Free Dynamic Range Two-tone IMD……..

4 Frequency Domain Analysis
Fundamental Signal Magnitude Harmonics Spurious H H H H5 Noise Ft (M) Frequency

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。

6 动态特性的测试方法（2） Clock Source Analog Source DUT (ADC) n bits Digital
Capture Data Processing (FFT) Sinusoidal Wave Frequency Spectrum

7 RXADC 测试环境要求（1） Input signal requests：
1：Quality of signal：SNR, THD…… ：Amplitude , frequency and common voltage of signal . 3：four orthogonal differential signals；

8 RXADC 测试环境要求（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

9 Coherent sampling

10 Uncoherent sampling

11 Windowing

12 RXADC 测试环境要求（3） 在rxadc的测试中， Fin= Ncycle * Fsample / Nrecord Fin (kHz)
Fsamp (kHz) Nrecord Ncycle 600 23 89 133

13 RXADC 测试环境要求（4） Spectral leakage
sample sequence not meets coherent sampling Windowing minimizes spectral leakage

14 Window function Window types: Rectangular, Hamming , Hanning, Blackman …… 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 test

15 Windows function

16 Windows function

17 Calculation (1): FFT Ps = sum{Pf(m-k):1:Pf(m+k)}; Pdc = sum{Pf(1:k)};
Ph = sum{Ph(2:n)} ; Ph(i)= sum{Ph(i-1:i+1)}; Pn = sum(Pf) - Ps- Pdc – Ph; Signal bin 的选择：

18 Calculation (2): FFT S/N = 10* log(Ps/Pn);
SINAD = 10* log[Ps/(Pn+Ph)]; THD = 10* log(Ph/Ps); SFDR = 10* log[Ps / Pmax.spurious Level]； ENOB = (SINAD )/ 6.02

19 Signal bin S/N = 10* log(Ps/Pn); =====
= 10*log[10/9]+log(Ps/Pn) = S/N

20 I/Q match An ideal sinusoidal I/Q signal pair :
y(t) =   A exp(i(ωt + φ))   =   A cos(ωt + φ)   +   i A sin(ωt + φ)

21 I/Q mismatch Amplitude mismatch α and phase mismatch ε :
y(t)   =   A cos(ωt + φ)   +   i α A sin(ωt + φ + ε) = (1 + α exp(i ε)) A exp(i(ωt + φ))   +   0.5 (1 - α exp(-i ε)) A exp(-i(ωt + φ))

22 I/Q mismatch calculation
Amplitude α=20log(Iamp/Qamp);