基于美信代碼改的，原理是碼密度圖，將正弦波轉為對應的碼密度函數(shù)曲線，再對經(jīng)過ADC轉換的數(shù)字碼進行統(tǒng)計。輸入同樣是數(shù)字碼經(jīng)過權重累加的階梯圖。

function? my_dnlinl(D_codeWeight,FFTN,Resol)

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%? ? ? ? ? ? ? ? ? ?DNL & INL ,method.two? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?%?

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%用于計算INL和DNL的％代碼密度/直方圖測試需要大量樣本。

%步驟1：施加接近滿量程的正弦波（但不削波），并找到所施加信號的中間碼。

%步驟2：施加相同的正弦波輸入，但幅度稍大些，以對ADC進行稍稍削波。

%FFTN = OSR*(2^Resol);

mid_code=0.5*(max(D_codeWeight)-min(D_codeWeight));%不需要取整！

% D_codeWeight = D_bits_record*DACWeight;

D_codeWeightCount=zeros(1,2^Resol);

for SamPoint =1:FFTN % FFTN個，D_codeWeight為量化權重，為橫坐標

? ? D_codeWeightCount(D_codeWeight(SamPoint)+1) =D_codeWeightCount(D_codeWeight(SamPoint)+1)+1;

end

if D_codeWeightCount(1) == 0 || D_codeWeightCount(2^Resol) == 0 || ...

? (D_codeWeightCount(1) < D_codeWeightCount(2)) || (D_codeWeightCount(2^Resol-1) > D_codeWeightCount(2^Resol))

? ?disp('ADC not clipping ... Increase sinewave amplitude!');

end

A_Weight=max(mid_code,2^Resol-1-mid_code)+0.1; %權重

Vi_diff=(0:2^Resol-1)-mid_code; %差分權重,只能是0：4095，減4095/2，不能1：4096

sin2ramp=1./(pi*sqrt(A_Weight^2*ones(size(Vi_diff))-Vi_diff.*Vi_diff));

%求出正弦波密度曲線后再乘以總采樣次數(shù)FFTN，得到每個碼的概率次數(shù)

while sum(D_codeWeightCount(2:2^Resol-1)) < FFTN*sum(sin2ramp(2:2^Resol-1))

? A_Weight=A_Weight+0.1;

? sin2ramp=1./(pi*sqrt(A_Weight^2*ones(size(Vi_diff))-Vi_diff.*Vi_diff));

end

%? figure

%? plot((0:2^Resol-1),sin2ramp)%sine波的碼密度曲線，但是曲線為什么不對稱？

% 因為mid_code取整了，不能取整

% xlim([-400,4500]);

%disp('You Have Applied a Sine Wave of (dBFS): ');?

Amplitude=A_Weight/(2^Resol/2);%美信原代碼可能有用，改寫之后用不到

figure;

set(gcf, 'Position', [100, 100, 1000, 400]);

subplot(1,2,1)

plot((1:2^Resol),D_codeWeightCount)

xlim([0,2^Resol]);

subplot(1,2,2)

plot((1:2^Resol),sin2ramp*FFTN);

xlim([0,2^Resol]);

%axis([0 2^Resol-1 0 max(D_codeWeightCount)]);

%%%%%%%%%? ?DNL? ?%%%%%%%%%

D_codeWeightCountDiv=D_codeWeightCount(2:2^Resol-1)./(FFTN*sin2ramp(2:2^Resol-1));?

%去頭去尾

figure;

plot(D_codeWeightCountDiv(1:2^Resol-2));%即原來的2：2^Resol-1

title('CODE HISTOGRAM - NORMALIZED')

xlabel('DIGITAL OUTPUT CODE');

ylabel('NORMALIZED COUNTS');

dnl=D_codeWeightCountDiv-1;

%%%%%%%%%? ?INL? ?%%%%%%%%%

inl=zeros(size(dnl));

for Q=1:length(dnl)

? ?inl(Q)=sum(dnl(1:Q));

end

%INL with end-points fit, i.e. INL=0 at end-points the straight line joining the 2 end points

%[p,S]=polyfit([1,2^numbit-2],[inl(1),inl(2^numbit-2)],1);

%the best-fit straight line

[p,S]=polyfit([1:2^Resol-2],inl,1);

inl=inl-p(1)*[1:2^Resol-2]-p(2);

%disp('End Points Eliminated for DNL and INL Calculations');

figure;

set(gcf, 'Position', [100, 100, 1000, 400]);

subplot(2,1,1)

plot(dnl(1:2^Resol-2));

grid on;

title('DIFFERENTIAL NONLINEARITY vs. DIGITAL OUTPUT CODE');

xlabel('DIGITAL OUTPUT CODE');

ylabel('DNL (LSB)');

xlim([0,2^Resol]);

ylim([min(dnl)-0.25,max(dnl)+0.25])

subplot(2,1,2)

plot(inl(1:2^Resol-2));

grid on;

title('INTEGRAL NONLINEARITY vs. DIGITAL OUTPUT CODE');

xlabel('DIGITAL OUTPUT CODE');

ylabel('INL(LSB)');?

xlim([0,2^Resol]);

ylim([min(inl)-0.25,max(inl)+0.25])

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end