mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-15 16:42:12 -05:00
ecfc15f3e4
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@3470 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
67 lines
1.6 KiB
Fortran
67 lines
1.6 KiB
Fortran
subroutine downsam9(id2,npts8,nsps8,newdat,nspsd,fpk,c2,nz2)
|
|
|
|
!Downsample from id2() into C2() so as to yield nspsd samples per symbol,
|
|
!mixing from fpk down to zero frequency.
|
|
|
|
include 'constants.f90'
|
|
parameter (NMAX1=1024*1920)
|
|
integer*2 id2(0:8*npts8-1)
|
|
real*4 x1(0:NMAX1-1)
|
|
complex c1(0:NMAX1/2)
|
|
complex c2(0:4096-1)
|
|
real s(5000)
|
|
equivalence (c1,x1)
|
|
save
|
|
|
|
nfft1=1024*nsps8 !Forward FFT length
|
|
df1=12000.0/nfft1
|
|
npts=8*npts8
|
|
|
|
if(newdat.eq.1) then
|
|
fac=6.963e-6 !Why this weird constant?
|
|
do i=0,npts-1
|
|
x1(i)=fac*id2(i)
|
|
enddo
|
|
x1(npts:nfft1-1)=0. !Zero the rest of x1
|
|
call timer('fft_forw',0)
|
|
call four2a(c1,nfft1,1,-1,0) !Forward FFT, r2c
|
|
call timer('fft_forw',1)
|
|
|
|
nadd=1.0/df1
|
|
s=0.
|
|
do i=1,5000
|
|
j=(i-1)/df1
|
|
do n=1,nadd
|
|
j=j+1
|
|
s(i)=s(i)+real(c1(j))**2 + aimag(c1(j))**2
|
|
enddo
|
|
enddo
|
|
endif
|
|
|
|
ndown=8*nsps8/nspsd !Downsample factor
|
|
nfft2=nfft1/ndown !Backward FFT length
|
|
nh2=nfft2/2
|
|
nf=nint(fpk)
|
|
i0=fpk/df1
|
|
|
|
nw=100
|
|
ia=max(1,nf-nw)
|
|
ib=min(5000,nf+nw)
|
|
call timer('pctile_1',0)
|
|
call pctile(s(ia),ib-ia+1,40,avenoise)
|
|
call timer('pctile_1',1)
|
|
|
|
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 timer('fft_back',0)
|
|
call four2a(c2,nfft2,1,1,1) !FFT back to time domain
|
|
call timer('fft_back',1)
|
|
nz2=8*npts8/ndown
|
|
|
|
return
|
|
end subroutine downsam9
|