Code covered by the BSD License

# Delta Sigma Toolbox

### Richard Schreier (view profile)

• 1 file
• 4.58904

14 Jan 2000 (Updated )

High-level design and simulation of delta-sigma modulators

### Editor's Notes:

This file was selected as MATLAB Central Pick of the Week

frespHBF(f,f1,f2,phi,fp,msg)
```function [mag,pbr,sbr] = frespHBF(f,f1,f2,phi,fp,msg)
%[mag pbr sbr] = frespHBF(f,f1,f2,phi,fp,msg)
%Compute the frequency response, the passband ripple and the stopband ripple
% of a Saramaki HBF. If msg is non-null, a plot is made.
% fp is the passband edge.
% phi is used by designHBF.

% Handle the input arguments
parameters = {'f' 'f1' 'f2' 'phi' 'fp' 'msg'};
defaults = { NaN NaN NaN 1 0.2 '' };
for i=1:length(defaults)
parameter = char(parameters(i));
if i>nargin | ( eval(['isnumeric(' parameter ') '])  &  ...
eval(['any(isnan(' parameter ')) | isempty(' parameter ') ']) )
eval([parameter '=defaults{i};'])
end
end
if isnan(f)
f = linspace(0,.5,1024);
end
if isstruct(f1)	% Presume that f1 is a {.val,.csd} struct
f1 = [f1.val];
end
if isstruct(f2)	% Presume that f2 is a {.val,.csd} struct
f2 = [f2.val];
end
f1 = f1(:); f2 = f2(:);

Npts = length(f);
w = 2*pi*f;
z = exp(j*w);
cos_w = real(z);

n2 = length(f2);
F2 = zeros(size(w));
for i = 1:n2
F2 = F2 + f2(i)*cos(w*(2*i-1));
end
F2 = F2*2;
mag = evalF1(f1,F2);

if nargout > 1 | ~isempty(msg)
passband = 1:floor(2*fp*(Npts-1) +1);
stopband = Npts + 1 - passband;
pbr = max( abs( abs(mag(passband)) -1 ) );
sbr = max( abs(mag(stopband)) );
end

if ~isempty(msg)
clf
subplot(211)
F1 = evalF0(f1,z,phi);
hndl(1) = plot(f,abs(F1),'--'); hold on;
hndl(2) = plot(f,phi*abs(F2),':');
hndl(3) = plot(f, abs(mag),'-'); hold off;
legend(hndl,'F1','F2','HBF')
title(msg);
hold on; grid on
axis([0 0.5 0 1.1])

subplot(212)
plot(f,dbv(mag))
axis([0 0.5 -150 10])
grid on

msg = sprintf( ' pbr=%.1e', pbr );
text(0.0, -10, msg, 'VerticalAlignment', 'top');
msg = sprintf( 'sbr=%.0fdB ', dbv(sbr) );
text(0.5, dbv(sbr), msg, 'HorizontalAlignment', 'right', ...
'VerticalAlignment', 'bottom');
drawnow;