function H=hpf(c0,c1,c2,c3,N)

for k=1:N/2 -1,
H=[H;zeros(1,2*(k-1)),c3,-c2,c1,-c0,zeros(1,N-(4+2*(k-1)))];
end

H=[H;c1,-c0,zeros(1,N-4),c3,-c2];
