WSJT-X/lib/sync65.f90

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subroutine sync65(ss,nfa,nfb,naggressive,ntol,nhsym,ca,ncand,nrobust, &
single_decode)
parameter (NSZ=3413,NFFT=8192,MAXCAND=300)
real ss(322,NSZ)
real ccfblue(-11:540) !CCF with pseudorandom sequence
real ccfred(NSZ) !Peak of ccfblue, as function of freq
logical single_decode
type candidate
real freq
real dt
real sync
real flip
end type candidate
type(candidate) ca(MAXCAND)
common/steve/thresh0
if(ntol.eq.-99) stop !Silence compiler warning
call setup65
df=12000.0/NFFT !df = 12000.0/8192 = 1.465 Hz
ia=max(2,nint(nfa/df))
ib=min(NSZ-1,nint(nfb/df))
lag1=-11
lag2=59
nsym=126
ncand=0
fdot=0.
ccfred=0.
ccfblue=0.
ccfmax=0.
ipk=0
do i=ia,ib
call xcor(ss,i,nhsym,nsym,lag1,lag2,ccfblue,ccf0,lagpk0,flip,fdot,nrobust)
! Remove best-fit slope from ccfblue and normalize so baseline rms=1.0
if(.not.single_decode) call slope(ccfblue(lag1),lag2-lag1+1, &
lagpk0-lag1+1.0)
ccfred(i)=ccfblue(lagpk0)
if(ccfred(i).gt.ccfmax) then
ccfmax=ccfred(i)
ipk=i
endif
enddo
call pctile(ccfred(ia:ib),ib-ia+1,35,xmed)
ccfred(ia:ib)=ccfred(ia:ib)-xmed
ccfred(ia-1)=ccfred(ia)
ccfred(ib+1)=ccfred(ib)
do i=ia,ib
freq=i*df
itry=0
! if(naggressive.gt.0 .and. ntol.lt.1000 .and. ccfmax.ge.thresh0) then
if(naggressive.gt.0 .and. ccfmax.ge.thresh0) then
if(i.ne.ipk) cycle
itry=1
ncand=ncand+1
else
if(ccfred(i).ge.thresh0 .and. ccfred(i).gt.ccfred(i-1) .and. &
ccfred(i).gt.ccfred(i+1)) then
itry=1
ncand=ncand+1
endif
endif
if(itry.ne.0) then
call xcor(ss,i,nhsym,nsym,lag1,lag2,ccfblue,ccf0,lagpk,flip,fdot, &
nrobust)
if(.not.single_decode) call slope(ccfblue(lag1),lag2-lag1+1, &
lagpk-lag1+1.0)
xlag=lagpk
if(lagpk.gt.lag1 .and. lagpk.lt.lag2) then
call peakup(ccfblue(lagpk-1),ccfmax,ccfblue(lagpk+1),dx2)
xlag=lagpk+dx2
endif
dtx=xlag*2048.0/11025.0
ccfblue(lag1)=0.
ccfblue(lag2)=0.
ca(ncand)%freq=freq
ca(ncand)%dt=dtx
ca(ncand)%flip=flip
if(single_decode) then
ca(ncand)%sync=db(ccfred(i)) - 16.0
else
ca(ncand)%sync=ccfred(i)
endif
endif
if(ncand.eq.MAXCAND) exit
enddo
return
end subroutine sync65