WSJT-X/lib/sync9.f90

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subroutine sync9(ss,tstep,df3,ntol,nfqso,sync,snr,fpk,ccfred)
parameter (NSMAX=22000) !Max length of saved spectra
real ss(184,NSMAX)
real ccfred(NSMAX)
integer ii(16) !Locations of sync half-symbols
data ii/1,11,21,31,41,51,61,77,89,101,113,125,137,149,161,169/
integer isync(85) !Sync vector for half-symbols
data isync/ &
1,0,0,0,0,1,0,0,0,0,1,0,0,0,0,1,0,0,0,0, &
1,0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,1,0, &
0,0,0,0,1,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0, &
0,0,1,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,0,0, &
1,0,0,0,1/
ipk=0
ipkbest=0
ia=1
ib=min(1000,nint(1000.0/df3))
if(ntol.lt.1000) then
ia=nint((nfqso-1000-ntol)/df3)
ib=nint((nfqso-1000+ntol)/df3)
if(ia.lt.1) ia=1
if(ib.gt.NSMAX) ib=NSMAX
endif
sbest=0.
lagmax=2.5/tstep + 0.9999
ccfred=0.
do i=ia,ib
smax=0.
do lag=-lagmax,lagmax
sum=0.
do j=1,16
k=ii(j) + lag
if(k.ge.1) sum=sum + ss(k,i)
enddo
if(sum.gt.smax) then
smax=sum
ipk=i
lagpk=lag
endif
enddo
if(smax.gt.sbest) then
sbest=smax
ipkbest=ipk
! lagpkbest=lagpk
endif
ccfred(i)=smax
enddo
sum=0.
nsum=0
do i=ia,ib
if(abs(i-ipkbest).ge.2) then
sum=sum+ccfred(i)
nsum=nsum+1
endif
enddo
ave=sum/nsum
snr=10.0*log10(sbest/ave) - 10.0*log10(2500.0/df3)
sync=sbest/ave - 2.0
if(sync.lt.0.0) sync=0.0
if(sync.gt.10.0) sync=10.0
fpk=(ipkbest-1)*df3
return
end subroutine sync9