jens
1f5b0b0570
git-svn-id: http://moon:8086/svn/matlab/trunk@128 801c6759-fa7c-4059-a304-17956f83a07c
49 lines
1.0 KiB
Matlab
49 lines
1.0 KiB
Matlab
function [Bp,Ap] = boost3(fs, fc, bw, gain, P);
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%BOOST - Design a boost filter at given gain, center
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% frequency fc, bandwidth bw, and sampling rate fs
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% (default = 1).
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%
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% Cookbook formulae for audio EQ biquad filter coefficients
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% by Robert Bristow-Johnson <rbj@audioimagination.com>
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Q = bw/fs;
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Bp = zeros(P, 3);
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Ap = zeros(P, 3);
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for p=1:P,
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kp = IIRCalcQp(p, P);
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[Bp(p,:),Ap(p,:)] = peaking(fs, fc, kp*Q, gain);
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endfor
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B = Bp(1,:);
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A = Ap(1,:);
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if nargout==0
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close
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freqz(B,A);
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title('Boost Frequency Response')
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end
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endfunction
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function [B,A] = peaking(fs, fc, Q, K)
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k1=-cos(2*pi*fc/fs);
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if K < 1
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k2=(1-tan(Q/K/2))/(1+tan(Q/K/2));
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else
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k2=(1-tan(Q/2))/(1+tan(Q/2));
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end
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Pz = [1 k1*(1+k2) k2]; % define denominator coefficients
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Qz = [k2 k1*(1+k2) 1]; % define numerator coefficients
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Num = (Pz*(1+K) + Qz*(1-K))/2;
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Den = Pz;
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B = Num;
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A = Den;
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endfunction
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function kp = IIRCalcQp(p, P)
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kp = 1.0/(2*sin(pi*(2*p-1)/(2*P)));
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endfunction
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