dspfft.m

基于ADSP-219x系列的时间抽取基2FFT代码

c=[0.01 0.02 0.03 0.04 0.05 0.06]
X=8
Y=log(X)/log(2)
N=128
M=log(N)/log(2)
P=N/X
Q=log(P)/log(2)
for i=5:N
    c(i)=0
end 


a(1)=1
a(2)=2
for k=1:(M-1)
    for i=(2^k):-1:1
        a(2*i-1)=a(i)
    end 
    for j=0:(2^k-1)
        a(2*(j+1))=a(2*j+1)+2^k
    end
end
for i=1:N
    d(a(i),1)=c(i)
    d(i,2)=0
end

for i=0:7
    m=i*16+1
    for j=1:15
        n=m+j
        d(n,1)=d(m,1)
        d(n,2)=d(m,2)
    end 
end

for k=Q:(M-1)
    for i=1:2^k
        w(i,1)=cos(2*pi*(i-1)/2^(k+1))
        w(i,2)=-sin(2*pi*(i-1)/2^(k+1))
    end
    for j=1:2^(k+1):N
        for m=0:(2^k-1)
            s=j+m
            t=j+m+2^k
            a1=(d(s,1)+w(m+1,1)*d(t,1)-w(m+1,2)*d(t,2))
            a2=(d(s,2)+w(m+1,1)*d(t,2)+w(m+1,2)*d(t,1))
            b1=(d(s,1)-w(m+1,1)*d(t,1)+w(m+1,2)*d(t,2))
            b2=(d(s,2)-w(m+1,1)*d(t,2)-w(m+1,2)*d(t,1))
            d(s,1)=a1
            d(s,2)=a2
            d(t,1)=b1
            d(t,2)=b2
        end 
    end
end