when i run the main file it shows that the error came from the subfile which is the fB is undefined.can you tell me which part is wrong and how to correct it?thank you...

below is the code in the main file:

                             %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                          Example 4.11 Page 195                          %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                         %
%                           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
Amp=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);                            % Hanning window method
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,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/2 -140 0]);
sfdr=max(ptot(nper+4:N/2));
snr ;

below is the code for the subfile named calcSNR:

                                                                                                function [snrdB,ptotdB,psigdB,pnoisedB] = calcSNR(vout,f,fB,w,N)
% SNR calculation in the time domain (P. Malcovati, S.Brigati)
% function [snrdB,ptotdB,psigdB,pnoisedB] = calcSNR(vout,f,fB,w,N)
% 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
%
% snrdB:     SNR in dB
% ptotdB:    Bit-stream power spectral density (vector)
% psigdB:    Extracted signal power spectral density (vector)
% pnoisedB:  Noise power spectral density (vector)
%
fB=ceil(fB);
signal=(N/sum(w))*sinus(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)/sum(vout(1:N).^2)*N;    % 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

[Walter Roberson]

At the command line, give the command

dbstop if error

and then run the program. When it stops with the error, please show us the output of

dbstack