WSJT-X/libm65/syncmsk.f90

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subroutine syncmsk(cdat,npts,cwb,r,i1)
! Establish character sync within a JTMS ping.
complex cdat(npts) !Analytic signal
complex cwb(168) !Complex waveform for 'space'
real r(60000)
real tmp(60000)
integer hist(168),hmax(1)
complex z
r=0.
jz=npts-168+1
do j=1,jz
z=0.
ss=0.
do i=1,168
ss=ss + abs(cdat(i+j-1)) !Total power
z=z + cdat(i+j-1)*conjg(cwb(i)) !Signal matching <space>
enddo
r(j)=abs(z)/ss !Goodness-of-fit to <space>
! write(52,3001) j/168.0,r(j),cdat(j)
!3001 format(4f12.3)
enddo
ncut=99.0*float(jz-10)/float(jz)
call pctile(r,tmp,jz,ncut,rlim)
hist=0
do j=1,jz
k=mod(j-1,168)+1
if(r(j).gt.rlim) hist(k)=hist(k)+1
enddo
hmax=maxloc(hist)
i1=hmax(1)
return
end subroutine syncmsk