DAC 的SNR matlab help！

XD0909 · 發表於 2009-8-20 10:51:38

那位大大帮忙解释一下以下Code的意义。

clear all;

N=2^12;                      % The input sequence is made by 2^12 points
Nbit=8;                      % 8-bit DAC
Ntransient=11;                %
Ntot=N+Ntransient;
nper=311;                      % prime integer number of sine waveforms
Fs=1;
bw=0.5;
Fin=nper*Fs/N;                % Input signal frequency (Fin=nper*Fs/N)
Vref=0.5;                      % Full scale for an input sinewave
Amp_dB=-0;                   % Amplitude in dB
Ampl=10^(Amp_dB/20)*Vref;    % Input signal amplitude

finrad=Fin*2*pi;
alphadx=0.0001;                % gradient in the resistivity
den=2^Nbit-1+alphadx*2^Nbit*(2^Nbit-1)/2;

for i=1:Ntot,
x=Vref*sin(finrad*(i-1))+Vref;    % Unipolar range
k=round(x*2^Nbit);
vout=(k+alphadx*k*(k+1)/2)/den;
y(i)=vout;
end

y=y-mean(y)                         % Output with zero average

%--------------------------------Graphics---------------------------------%

figure(1);
clf;
plot(y,'r');
grid;
xlim([1600 1900]);
title('Sinewave with distortion');

w=ones(1,N);
f=Fin/Fs;                            % Normalized signal frequency
fB=N*(bw/Fs);                         % Base-band frequency bins
[snr,ptot]=calcSNR(y(1:N),f,fB,w,N);
ptot=ptot-max(ptot);                   % Normalize total spectrum

figure(2);
clf;
plot(linspace(0,Fs/2,N/2), ptot(1:N/2), 'r');
grid on;
title('PSD of the Output')
xlabel('Frequency [Hz]')
ylabel('PSD [dB]')
axis([0 Fs/4 -120 0]);
text(Fs/10,-20,sprintf('\\bfSNR = %3.1fdB  @  \\alpha\\DeltaX = %1.0e\n'...
,snr,alphadx),'Fontsize',12);
text(f*2,ptot((f*N+1)*2-1)+3,sprintf('\\bf%2.1fdB',ptot((f*N+1)*2-1)),...
'Fontsize',8,'HorizontalAlignment','center');

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[問題求助] DAC 的SNR matlab help！