# Help to plot the LED Characteristic Curve

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댓글: adriane duarte 2021년 9월 11일
I am trying to plot the LED characteristic curve, but I am not getting the correct curve.The theoretical curve is below. The curve I'm finding is this. A little different than expected. Someone could help me with what I'm wrong. I'm submitting my code below.
% LED information
Vt = 0.5;
Is = 0.5;
% LED model
K = 0.5;
imax = 0.5;
threshold = 150;
sigmaV2 = (imax./threshold).^2;
% number of bits
L = 1e4;
SNRdB = 40;
% Signal-to-Noise Ratio Lin.
SNR = 10.^(SNRdB/10);
r = 10.^(SNRdB/10);
% signal standard deviation (power)
sigmaX2v = SNR.*sigmaV2;
% Maximum number of iterations for a single SNR
max_run = 100;
for sk = 1:length(SNRdB)
for tk = 1:max_run
s = linspace(0,100,10000); % input
s1 = s.';
stdS = std(s1);
X = zeros(1,4.*L);
X(2:2:end) = [s1; conj(s1(end:-1:1))];
xTD = ifft(X);
xTD = (sqrt(sigmaX2v(sk))).*xTD./std(xTD);
xx = xTD;
ind = find(xTD < 0);
xx(ind) = zeros(size(ind));
ss = xx;
iLED = Is.*(exp(ss./Vt) - 1);
xLED = iLED./((1 + (iLED./imax).^(2.*K)).^(1./(2.*K)));
y = xLED;
Nframe = length(y);
Xhat = (fft(y)+10);
Shat = Xhat(2:2:Nframe/2);
Shat = stdS.*Shat./std(Shat);
Y = Shat; % output
end
end
plot(s1,Y)

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### 답변(1개)

Sulaymon Eshkabilov 2021년 9월 10일
The answer in signal-to-noise ratio value, e.g:
SNRdB = 20; % Gives a nice looking one!