function [a, b, err] = design_iirlpnorm(K)
%
% function [a, b] = design_iirlpnorm(K) 
%
% designs the Doppler Filter (IIR) as best as possible.
% K is the number of biquads, so, order is 2*K.
% Christos Komninakis, June 2003.
%
n = 2*K;
%
fD = 0.2; fDN = 2*0.2;
M = 1000;    % end up with M+1 frequency points, including 0 and 1.
L = floor(fDN*M);
A = sqrt(1./sqrt(1-([0:L-1]./L).^2));
A = [ A sqrt(L*(pi/2-asin((L-1)/L))) ];
A = [ A zeros(1,M-L) ];
F = [0:1/M:1];
edges = [0 F(L+1) F(L+2) 1];
weights = ones(1,length(F));
%
% Use the Matlab function iirlpnorm to design the filter
%
[b,a, err] = iirlpnorm(n,n, F, edges, A, weights);
[H,W,S] = freqz(b,a,1000);
plot(W/pi, 20*log10(abs(H))); grid on;