i got negative value for sfdr and snr=61.4315 which are not the desired answer.i don't know which part that must be fixed to get the value of sfdr=70.9 and snr=60.7

Question

lotus 2013-3-24

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/68395-i-got-negative-value-for-sfdr-and-snr-61-4315-which-are-not-the-desired-answer-i-don-t-know-which-pa

评论： ali 2014-1-14

-mainfile-

                                                                       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Example 4.11 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % Pipeline Converter % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%clear all;
                                                                                                %-------------------------------------------------------------------------%
%                         DAC Static parameters                           %
%-------------------------------------------------------------------------%
                                                                                                   %-------------------------------- Stage 1 --------------------------------%
V_DAC_L1=-0.5;
V_DAC_H1=0.5;
GAIN1=2.0;
VthL1=-0.25+eps;
VthH1=0.25+eps;
                                                                                             %-------------------------------- Stage 2 --------------------------------%
V_DAC_L2=-0.5;
V_DAC_H2=0.5;
GAIN2=2.0;
VthL2=-0.25+eps;
VthH2=0.25+eps;
                                                                                         %------------------------------- Stages 3-9 ------------------------------%
V_DAC_L3=-0.5;
V_DAC_H3=0.5;
GAIN3=2.0;
VthL3=-0.25+eps;
VthH3=0.25+eps;
                                                                                    Vth10=0;
                                                                                           %-------------------------------------------------------------------------%
%                             Dynamic parameters                          %
%-------------------------------------------------------------------------%
                                                                                           %-------------------------------- S&H Block-------------------------------%
srH=250e6;
f_TH=600e6;
betaH=1;
tauH=1/(2*pi*betaH*f_TH);
gainH=1;
                                                                                         %-------------------------------- Stage 1 --------------------------------%
sr1=10000e8;
f_T1=6000e6;
beta1=1/2;
tau1=1/(2*pi*beta1*f_T1);
gain1=1;
                                                                                           %-------------------------------- Stage 2 --------------------------------%
sr2=20000e8;
f_T2=6000e6;
beta2=1/2;
tau2=1/(2*pi*beta2*f_T2);
gain2=1;
                                                                                          %------------------------------- Stages 3-9 ------------------------------%
sr=25000e8;
f_T=6000e6;
beta=1/2;
tau=1/(2*pi*beta*f_T);
gain=1;
                                                                                             %-------------------------------------------------------------------------%
%                         Simulation parameters                           %
%-------------------------------------------------------------------------%
                                                                                         Ts=1e-8;
Tmax=Ts/2;
Vfs=2;
N=2^12;
Ntransient=20;         
Tstop=Ts*(N+Ntransient);
nper=73;
Fs=1/Ts;
Fin=nper*Fs/N;                 % Input signal frequency (Fin = nper*Fs/N)
f=Fin/Fs;                      % Normalized signal frequency
bw=Fs/2;
                                                                                                   Amp_dB=-0;                     % Amplitude in dB
Ampl=10^(Amp_dB/20)*Vfs/2;     % Input signal amplitude
                                                                                 finrad=Fin*2*pi;
                                       %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                           Launch Simulation                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
options=simset('InitialStep', 1, 'RelTol', 1e-3, 'MaxStep', 1,...
    'Fixedstep', 1);
sim('Ex4_11',Tstop, options);           %Starts Simulink simulation
                                                                                             %-------------------------------------------------------------------------% 
%                             Graphic Outputs                             %
%-------------------------------------------------------------------------%
w=hann(N);
f=Fin/Fs;                             % Normalized signal frequency
fB=N*(bw/Fs);                         % Base-band frequency bins
yfft=y(1+Ntransient:N+Ntransient);
[snr,ptot]=calcSNR(yfft',f,fB,w',N);
ptot=ptot-max(ptot);                  % Normalize total spectrum
                                                                                        figure(1);
clf;
plot(linspace(0,5E-9*Fs,N/2), ptot(1:N/2), 'r');
grid on;
title('PSD of the Output')
xlabel('Frequency [Hz]')
ylabel('PSD [dB]')
axis([0 5E-9*Fs -140 0]);
sfdr=max(ptot(nper+4:N/2)) 
snr

-subfile calcSNR-

                                                                                                                                                                      function [snrdB,ptotdB,psigdB,pnoisedB] = calcSNR(vout,f,fB,w,N,Vref)
% SNR calculation in the time domain (P. Malcovati, S. Brigati)
% vout: Sigma-Delta bit-stream taken at the modulator output
% f:    Normalized signal frequency (fs -> 1)
% fB:  Base-band frequency bins
% w:  windowing vector
% N:    samples number
% Vref: feedback reference voltage
%
% snrdB:    SNR in dB
% ptotdB:    Bit-stream power spectral density (vector)
% psigdB:   Extracted signal power spectral density (vector)
% pnoisedB:  Noise power spectral density (vector)
%
                                                                                        Vref=1|-1
fB=ceil(fB);
signal=(N/sum(w))*sinusx(vout(1:N).*w,f,N);  % Extracts sinusoidal signal
noise=vout(1:N)-signal;                  % Extracts noise components
stot=((abs(fft((vout(1:N).*w)'))).^2);    % Bit-stream PSD
ssignal=(abs(fft((signal(1:N).*w)'))).^2;  % Signal PSD
snoise=(abs(fft((noise(1:N).*w)'))).^2;    % Noise PSD
pwsignal=sum(ssignal(1:fB));              % Signal power
pwnoise=sum(snoise(1:fB));                % Noise power
snr=pwsignal/pwnoise;
snrdB=dbp(snr);
norm=sum(stot)/Vref^2;            % PSD normalization
if nargout > 1
  ptot=stot/norm; 
  ptotdB=dbp(ptot);
end
                                                                                                   if nargout > 2
  psig=ssignal/norm;
  psigdB=dbp(psig);
end
                                                                                                       if nargout > 3
  pnoise=snoise/norm;
  pnoisedB=dbp(pnoise);
end

-subfile dbp-

                                                                                                                                                                                                                       function y=dbp(x)
% dbp(x) = 10*log10(x): the dB equivalent of the power x
%y = -Inf*ones(size(x));
%nonzero = x~=0;
%y(nonzero) = 10*log10(abs(x(nonzero)));
y = 10*log10(abs(x(:)))';

it is very pleasure if someone can help me with this kind of problems.thanking you in advance.