WSJT-X/spec2d65.f
J C Dutton a39f662b4d Summary: Merge in linux branch
svn+ssh://svn.berlios.de/svnroot/repos/wsjt/WSJT/branches/linux
merged into
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git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/trunk@155 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2006-04-05 20:07:32 +00:00

85 lines
2.4 KiB
Fortran

subroutine spec2d65(dat,jz,nsym,flip,istart,f0,
+ ftrack,mode65,s2)
C Computes the spectrum for each of 126 symbols.
C NB: At this point, istart, f0, and ftrack are supposedly known.
C The JT65 signal has Sync bin + 2 guard bins + 64 data bins = 67 bins.
C We add 5 extra bins at top and bottom for drift, making 77 bins in all.
parameter (NMAX=2048) !Max length of FFTs
real dat(jz) !Raw data
real s2(77,126) !Spectra of all symbols
real s(77)
real ref(77)
real ps(77)
real x(NMAX)
real ftrack(126)
real*8 pha,dpha,twopi
complex cx(NMAX)
c complex work(NMAX)
include 'prcom.h'
equivalence (x,cx)
data twopi/6.28318530718d0/
save
nfft=2048/mode65 !Size of FFTs
nh=nfft/2
dt=2.0/11025.0
df=0.5*11025.0/nfft
call zero(ps,77)
k=istart-nfft
do j=1,nsym
call zero(s,77)
do m=1,mode65
k=k+nfft
if(k.ge.1 .and. k.le.(jz-nfft)) then
C Mix sync tone down to f=5*df (==> bin 6 of array cx, after FFT)
dpha=twopi*dt*(f0 + ftrack(j) - 5.0*df)
pha=0.0
do i=1,nfft
pha=pha+dpha
cx(i)=dat(k-1+i)*cmplx(cos(pha),-sin(pha))
enddo
call four2a(cx,nfft,1,-1,1)
do i=1,77
s(i)=s(i) + real(cx(i))**2 + aimag(cx(i))**2
enddo
else
call zero(s,77)
endif
enddo
call move(s,s2(1,j),77)
call add(ps,s,ps,77)
enddo
C Flatten the spectra by dividing through by the average of the
C "sync on" spectra, with the sync tone explicitly deleted.
nref=nsym/2
do i=1,77
C First we sum all the sync-on spectra:
ref(i)=0.
do j=1,nsym
if(flip*pr(j).gt.0.0) ref(i)=ref(i)+s2(i,j)
enddo
ref(i)=ref(i)/nref !Normalize
enddo
C Remove the sync tone itself:
base=0.25*(ref(1)+ref(2)+ref(10)+ref(11))
do i=3,9
ref(i)=base
enddo
C Now flatten the spectra for all the data symbols:
do i=1,77
fac=1.0/ref(i)
do j=1,nsym
s2(i,j)=fac*s2(i,j)
if(s2(i,j).eq.0.0) s2(i,j)=1.0 !### To fix problem in mfskprob
enddo
enddo
return
end