mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-24 05:08:38 -05:00
faa6b9d7af
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@2777 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
54 lines
1.2 KiB
Fortran
54 lines
1.2 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)
|
|
real s(1000)
|
|
|
|
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
|
|
|
|
ia=nint(250.0/df1)
|
|
nadd=1.0/df1
|
|
j=250/df1
|
|
s=0.
|
|
do i=1,1000
|
|
do n=1,nadd
|
|
j=j+1
|
|
s(i)=s(i)+real(c1(j))**2 + aimag(c1(j))**2
|
|
enddo
|
|
enddo
|
|
call pctile(s,1000,40,avenoise)
|
|
|
|
ndown=nsps8/16 !Downsample factor
|
|
nfft2=nfft1/ndown !Backward FFT length
|
|
nh2=nfft2/2
|
|
|
|
fshift=fpk-1500.0
|
|
i0=nh1 + fshift/df1
|
|
fac=sqrt(1.0/avenoise)
|
|
do i=0,nfft2-1
|
|
j=i0+i
|
|
if(i.gt.nh2) j=j-nfft2
|
|
c2(i)=fac*c1(j)
|
|
enddo
|
|
|
|
call four2a(c2,nfft2,1,1,1) !Backward FFT
|
|
|
|
nspsd=nsps8/ndown
|
|
nz2=npts8/ndown
|
|
|
|
return
|
|
end subroutine downsam9
|