How to use SDtoolbox for 24 bits ADC (second order delta sigma)

I prepare to design 24 bit ADC(use second order delta sigma, CIFB topology ), i use SDtoolbox, but it wrong.

Can everyone help me?

Code:

requirement: 24 bits, GBW:200MHz, Fs: 16,384Mhz

% 2nd Order Low-Pass Sigma-Delta Modulator Model % by S. Brigati, A. Fornasari, P. Malcovati % The modulator structure is simulated using Simulink (sd2mod.mdl). % 1. Plots the Power Spectral Density of the bit-stream % 2. Calculates the SNR % 3. Calculates histograms at the integrator outputs

clear

t0=clock;

% **********************************************************************

% Global variables

% **********************************************************************

bw=8e3; % Base-band

R=1024;

Fs=R*2*bw; % Oversampling frequency

Ts=1/Fs;

N=2^14; % Samples number

nper=187;

Fin=nper*Fs/N; % Input signal frequency (Fin = nper*Fs/N)

Ampl=1-pi/256; % Input signal amplitude [V]

Ntransient=0;

% % k=1.38e-23; % Boltzmann Constant

Temp=300; % Absolute Temperature in Kelvin

Cs=5e-13; % Integrating Capacitance of the first integrator

alfa=(1e4-1)/1e4; % A=Op-amp finite gain (alfa=(A-1)/A -> ideal op-amp alfa=1)

Amax=3.3; % Op-amp saturation value [V]

sr=20e6; % Op-amp slew rate [V/s]

GBW=200e6; % Op-amp GBW [Hz]

noise1=1e-5; % 1st int. output noise std. dev. [V/sqrt(Hz)]

delta=4e-6; % Random Sampling jitter (std. dev.) [s]

NCOMPARATORI=2; % Four bit quantizer

match=9e-10; % Realistic value, but not related to any technology (because of non disclosure agreement)

% Modulator coefficients

a1 = 0.25; b1 =0.75;

a2 = 0.25; b2 = 0.75; b3 =1;

c1 = 1; c2 = 1;

g1 = 0;

finrad=Fin*2*pi; % Input signal frequency in radians

s0=sprintf('** Simulation Parameters ');

s1=sprintf(' Fs(Hz)=%1.0f',Fs);

s2=sprintf(' Ts(s)=%1.6e',Ts);

s3=sprintf(' Fin(Hz)=%1.4f',Fin);

s4=sprintf(' BW(Hz)=%1.0f',bw);

s5=sprintf(' OSR=%1.0f',R);

s6=sprintf(' Npoints=%1.0f',N);

s7=sprintf(' tsim(sec)=%1.3f',N/Fs);

s8=sprintf(' Nperiods=%1.3f',N*Fin/Fs);

disp(s0)

disp(s1)

disp(s2)

disp(s3)

disp(s4)

disp(s5)

disp(s6)

disp(s7)

disp(s8)

% **********************************************************************

% Open Simulink diagram first

% *************************************************************** *****

open_system('untitled')

options=simset('InitialState', zeros(1,3), 'RelTol', 1e-3, 'MaxStep', 1/Fs);

sim('untitled', (N+Ntransient)/Fs, options); % Starts Simulink simulation

% **********************************************************************

% Calculates SNR and PSD of the bit-stream and of the signal

% **********************************************************************

w=hann_pv(N);

f=Fin/Fs; % Normalized signal frequency

fB=N*(bw/Fs); % Base-band frequency bins

yy1=zeros(1,N);

yy1=yout(2+Ntransient:1+N+Ntransient)';

ptot=zeros(1,N);

[snr,ptot]=calcSNR(yy1(1:N),f,1,fB,w,N);

Rbit=(snr-1.76)/6.02 % Equivalent resolution in bits

% % **********************************************************************

% % Output Grafico

% % **********************************************************************

% figure(1);

% clf;

% plot(linspace(0,Fs/2,N/2), ptot(1:N/2), 'r');

% grid on;

% title('PSD of a 2nd-Order Sigma-Delta Modulator')

% xlabel('Frequency [Hz]')

% ylabel('PSD [dB]')

% axis([0 Fs/2 -200 0]);

% figure(2);

% clf;

% semilogx(linspace(0,Fs/2,N/2), ptot(1:N/2), 'r');

% grid on;

% title('PSD of a 2nd-Order Sigma-Delta Modulator')

% xlabel('Frequency [Hz]')

% ylabel('PSD [dB]')

% axis([0 Fs/2 -200 0]); % figure(3);

clf;

plot(linspace(0,Fs/2,N/2), ptot(1:N/2), 'r');

hold on; title('PSD of a 2nd-Order Sigma-Delta Modulator (detail)')

xlabel('Frequency [Hz]')

ylabel('PSD [dB]') axis([0 2*(Fs/R) -200 0]); grid on; hold off; text_handle = text(floor(Fs/R),-40, sprintf('SNR = %4.1fdB @ OSR=%d\n',snr,R));

text_handle = text(floor(Fs/R),-60, sprintf('ENOB = %2.2f bits @ OSR=%d\n',Rbit,R));

s1=sprintf(' SNR(dB)=%1.3f',snr);

s2=sprintf(' Simulation time =%1.3f min',etime(clock,t0)/60);

disp(s1) disp(s2)

% ********************************************************************** % Histograms of the integrator outputs % **********************************************************************

% figure(4)

% nbins=200;

% [bin1,xx1]=histo(y1, nbins); % [bin2,xx2]=histo(y2, nbins); % clf;

% subplot(1,2,1), plot(xx1, bin1)

% grid on;

% title('First Integrator Output')

% xlabel('Voltage [V]')

% ylabel('Occurrences')

% subplot(1,2,2), plot(xx2, bin2)

% grid on;

% title('Second Integrator Output')

% xlabel('Voltage [V]')

% ylabel('Occurrences')

Answer 1

[XING HUANG]

What is the problem you have met?