WSJT-X/lib/mixlpf.f90

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Fortran
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subroutine mixlpf(x1,nbfo,c0)
real*4 x1(512)
real*8 twopi,phi,dphi
complex c1(512),c2(105+512)
complex c0(64)
data phi/0.d0/
save phi,c2
twopi=8.d0*atan(1.d0)
dphi=twopi*nbfo/12000.d0
do i=1,512
phi=phi+dphi
if(phi.gt.twopi) phi=phi-twopi
xphi=phi
c1(i)=x1(i)*cmplx(cos(xphi),sin(xphi))
enddo
c2(106:105+512)=c1
call fil3c(c2,105+512,c0,n2)
c2(1:105)=c1(512-104:512) !Save 105 trailing samples
return
end subroutine mixlpf