%% Transform Lowpass Filter to Complex Multiband Filter
% Design a prototype real IIR lowpass elliptic filter with a gain of about –3 dB at 0.5π rad/sample.

[b,a] = ellip(3,0.1,30,0.409);

%
% Create a complex multiband filter with two passbands.

[num,den] = iirlp2mbc(b,a,0.5,[-7 -5 6 8]/10);

%
% Compare the magnitude responses of the filters using FVTool. iirlp2mbc replicates the desired feature at 0.5 in the lowpass filter at four locations in the multiband filter.

hvft = fvtool(b,a,num,den);
legend(hvft,'Prototype','Target')

% Copyright 2012 The MathWorks, Inc.