mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-10-03 18:46:54 -04:00
4f34b46084
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@2775 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
47 lines
1.1 KiB
Fortran
47 lines
1.1 KiB
Fortran
subroutine downsam9(c0,npts8,nsps8,nspsd,fpk,c2,nz2)
|
|
|
|
!Downsample to nspsd samples per symbol, info centered at fpk
|
|
|
|
parameter (NMAX=128*31500)
|
|
complex c0(0:npts8-1)
|
|
complex c1(0:NMAX-1)
|
|
complex c2(0:4096-1)
|
|
|
|
fac=1.e-4
|
|
c1(0:npts8-1)=fac*c0 !Copy c0 into c1
|
|
do i=1,npts8-1,2
|
|
c1(i)=-c1(i)
|
|
enddo
|
|
c1(npts8:)=0. !Zero the rest of c1
|
|
nfft1=128*nsps8 !Forward FFT length
|
|
nh1=nfft1/2
|
|
df1=1500.0/nfft1
|
|
call four2a(c1,nfft1,1,-1,1) !Forward FFT
|
|
|
|
! do i=0,nfft1-1
|
|
! f=i*df1
|
|
! pp=real(c1(i))**2 + aimag(c1(i))**2
|
|
! write(50,3009) i,f,1.e-6*pp
|
|
!3009 format(i8,f12.3,f12.3)
|
|
! enddo
|
|
|
|
ndown=nsps8/16 !Downsample factor
|
|
nfft2=nfft1/ndown !Backward FFT length
|
|
nh2=nfft2/2
|
|
|
|
fshift=fpk-1500.0
|
|
i0=nh1 + fshift/df1
|
|
do i=0,nfft2-1
|
|
j=i0+i
|
|
if(i.gt.nh2) j=j-nfft2
|
|
c2(i)=c1(j)
|
|
enddo
|
|
|
|
call four2a(c2,nfft2,1,1,1) !Backward FFT
|
|
|
|
nspsd=nsps8/ndown
|
|
nz2=npts8/ndown
|
|
|
|
return
|
|
end subroutine downsam9
|