ADC测试matlab代码

前面有做过ADC性能测试，测试方式是先使用ADC采集一个单频信号，然后利用matlab进行性能分析。

下面把matlab分析的代码记录下来：

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1 %The following program code plots the FFT spectrum of a desired test tone. Test tone based on coherent sampling criteria, and
2 %computes SNR, SINAD, THD and SFDR.
3 %This program is believed to be accurate and reliable. This program may get altered without prior notification.;
4
5 %fid=fopen(‘F:\pelican_ADC_test\vjtag_prj\data_analysis\single_tone.txt’,‘r’);
6 %numpt=input(‘Number of Points in FFT? ‘);
7 %fclk=input(‘Sampling Frequency (MHz)? ‘);
8 %numbit=input(‘ADC Resolution (bits)? ‘);
9 close all;
10 clear all;
11
12 numpt=4096;
13 fclk=455/16;
14 % fclk=455/16/14;
15 numbit=12;
16
17 % a=textread(‘dds_data_out.txt’,’%s’)’;%以字符形式打开文件
18 % a=dlmread(‘sample_data.txt’,’%s’)’;%以字符形式打开文件
19 a=dlmread(‘sample_data.txt’,‘%s’)‘;%以字符形式打开文件
20 v1=a’; %16进制转化为10进制数，存储进v1矩阵
21 % for i = 1:numpt
22 % v1(i) = bitxor(v1(i),15872);
23 % end
24
25 %v1 is a column vector(1:numpt), and count is its length
26 %v1=dlmread(‘F:\pelican_ADC_test\vjtag_prj\data_analysis\single_tone.txt’,‘’);
27 %fclose(fid);
28 %change v1 into a row vector
29 code=v1’;
30
31 %Warning: ADC output may be clipping - reduce input amplitude
32 if (max(code)==2^numbit-1) | (min(code)==0)
33 disp(‘WARNING: ADC OUTPUT MAYBE CLIPPING - CHECK INPUT AMPLITUDE!’);
34 end
35
36 figure;
37 plot(code);
38 title(‘TIME DOMAIN’)
39 xlabel(‘SAMPLES’);
40 ylabel(‘DIGITAL OUTPUT CODE’);
41 Dout=code-(2^numbit-1)/2; %Re-center the digitized sinusoidal input
42 Voltage=Dout./((2^numbit-1)/2)(0.5);
43 figure;
44 plot([1:numpt],Voltage);
45
46 Doutw=(Dout’).blackmanharris(numpt); %add Minimum 4-term Blackman-Harris window
47 Dout_spect=fft(Doutw);
48 Dout_dB=20log10(abs(Dout_spect));
49
50 figure;
51 maxdB=max(Dout_dB(1:numpt/2)); %numpt points FFT result in numpt/2 points spectrum
52
53 %计算距离满量程的幅度差
54 max_voltage=max(Voltage);
55 delta_amplitude=20log10(max_voltage/0.5); %full scale voltage amplitude is 0.5v
56
57 plot([0:numpt/2-1].fclk/numpt,Dout_dB(1:numpt/2)-maxdB+delta_amplitude);
58 grid on;
59 title(‘SINGLE TONE FFT PLOT’);
60 xlabel(‘ANALOG INPUT FREQUENCY (MHz)’);
61 ylabel(‘AMPLITUDE (dBfs)’);
62 a1=axis; axis([a1(1) a1(2) -140 a1(4)]);
63 fin=find(Dout_dB(1:numpt/2)==maxdB); %Find the signal bin (DC represents bin=1)
64 DC_span=6; %default DC leakage bins are 6 bins
65 signal_span = 10; %signal leakage bins are ±10 bins for minumun 4-term black-harris window
66 spanh=3; %%default harmonic leakage bins are ±3 bins
67 spectP=(abs(Dout_spect)).(abs(Dout_spect));
68 %Determine power level
69 Pdc=sum(spectP(1:DC_span)); %Determine DC offset power level
70 Ps=sum(spectP(fin-signal_span:fin+signal_span)); %Determine signal power level
71 Fh=[];
72 %Vector storing frequency and power components of signal and harmonics
73 Ph=[]; %HD1=signal, HD2=2nd harmonic, HD3=3rd harmonic, etc.
74
75 %Find the harmonic frequencies/power within the FFT plot
76 for har_num=1:10
77 tone=rem((har_num*(fin- 1)+1)/numpt,1); %Note: tones > fSAMPLE are aliased back
78 if tone>0.5
79 tone=1-tone;
80 end
81 Fh=[Fh tone];
82
83 %For this method to work properly, make sure that the folded back high order harmonics do not overlap with DC and signal
84 %components or lower order harmonics.
85 har_peak=max(spectP(round(tonenumpt)-spanh:round(tonenumpt)+spanh));
86 har_bin=find(spectP(round(tonenumpt)-spanh:round(tonenumpt)+spanh)==har_peak);
87 har_bin=har_bin+round(tonenumpt)-spanh- 1; %make sure that the folded back high order harmonics do not overlap with DC and signal components or lower order harmonics
88 Ph=[Ph sum(spectP(har_bin-3:har_bin+3))];
89 end
90
91 Pd=sum(Ph(2:10)); %Total distortion power level
92 Pn=sum(spectP(1:numpt/2))-Pdc-Ps-Pd; %Extract noise power level
93 format;
94 A=(max(code)-min(code))/(2^numbit) %Analog input amplitude in mV
95 AdB=20log10(A) %Analog input amplitude in dB
96 SNR=10log10(Ps/Pn) %SNR in dB
97 SINAD=10log10(Ps/(Pn+Pd)) %SINAD in dB
98 disp(‘THD - HD2 through HD9’);
99 THD=10log10(Pd/Ph(1)) %THD in dB
100 SFDR=10log10(Ph(1)/max(Ph(2:10))) %SFDR in dB
101 disp(‘SIGNAL AND HARMONIC POWER (dB)’);
102 HD=10*log10(Ph(1:10)/Ph(1))
103
104 hold on;
105 plot(Fh(2)*fclk,-70,‘bo’,Fh(3)*fclk,-70,‘bx’,Fh(4)*fclk,-70,‘b+’,Fh(5)fclk,-70,'b’,Fh(6)*fclk,-70,‘bs’,Fh(7)*fclk,-70,‘bd’,Fh(8)*fclk,-70,‘bv’,Fh(9)*fclk,-70,‘b^’);
106 legend(‘SIGNAL’,‘HD2’,‘HD3’,‘HD4’,‘HD5’,‘HD6’,‘HD7’,‘HD8’,‘HD9’);
107 hold off;