WSJT-X/lib/spec9.f90

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Fortran
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subroutine spec9(c0,npts8,nsps,fpk0,fpk,xdt,snrdb,i1SoftSymbols)
parameter (MAXFFT=31500)
complex c0(0:npts8-1)
complex c1(0:2700000)
real ssym(0:7,69)
complex c(0:MAXFFT-1)
integer*1 i1SoftSymbolsScrambled(207)
integer*1 i1SoftSymbols(207)
integer*1 i1
integer ig(0:7)
equivalence (i1,i4)
data ig/0,1,3,2,7,6,4,5/ !Gray code removal
include 'jt9sync.f90'
save
! Fix up the data in c0()
sum=0.
do i=0,npts8-1
sum=sum + real(c0(i))**2 + aimag(c0(i))**2
enddo
rms=sqrt(sum/npts8)
fac=1.0/rms
twopi=8.0*atan(1.0)
phi=0.
dphi=twopi*500.0/1500.0
do i=0,npts8-1
phi=phi+dphi
if(phi.gt.twopi) phi=phi-twopi
if(phi.lt.-twopi) phi=phi+twopi
c1(i)=fac*cmplx(aimag(c0(i)),real(c0(i)))*cmplx(cos(phi),sin(phi))
enddo
nsps8=nsps/8
foffset=fpk0
istart=1520
call peakdf9(c1,npts8,nsps8,istart,foffset,idf)
fpk=fpk0 + idf*0.1*1500.0/nsps8
foffset=foffset + idf*0.1*1500.0/nsps8
call peakdt9(c1,npts8,nsps8,istart,foffset,idt)
istart=istart + 0.0625*nsps8*idt
xdt=istart/1500.0 - 1.0
fshift=foffset
twopi=8.0*atan(1.0)
dphi=twopi*fshift/1500.0
nfft=nsps8
nsym=min((npts8-istart)/nsps8,85)
k=0
do j=1,nsym
if(isync(j).eq.1) cycle
k=k+1
ia=(j-1)*nsps8 + istart
ib=ia+nsps8-1
c(0:nfft-1)=c1(ia:ib)
phi=0.
do i=0,nfft-1
phi=phi + dphi
c(i)=c(i) * cmplx(cos(phi),-sin(phi))
enddo
call four2a(c,nfft,1,-1,1)
do i=0,nfft-1
sx=real(c(i))**2 + aimag(c(i))**2
if(i.ge.1 .and. i.le.8) ssym(ig(i-1),k)=sx
enddo
enddo
sum=0.
sig=0.
do j=1,69
smax=0.
do i=0,7
smax=max(smax,ssym(i,j))
sum=sum+ssym(i,j)
enddo
sig=sig+smax
sum=sum-smax
enddo
ave=sum/(69*7)
ssym=ssym/ave
sig=sig/69.
df8=1500.0/nsps8
t=max(1.0,sig/ave - 1.0)
snrdb=db(t) - db(2500.0/df8)
m0=3
ntones=8
k=0
do j=1,69
do m=m0-1,0,-1 !Get bit-wise soft symbols
n=2**m
r1=0.
r2=0.
do i=0,ntones-1
if(iand(i,n).ne.0) then
r1=max(r1,ssym(i,j))
else
r2=max(r2,ssym(i,j))
endif
enddo
k=k+1
i4=nint(10.0*(r1-r2))
if(i4.lt.-127) i4=-127
if(i4.gt.127) i4=127
i4=i4+128
i1SoftSymbolsScrambled(k)=i1
enddo
enddo
call interleave9(i1SoftSymbolsScrambled,-1,i1SoftSymbols)
call flush(81)
call flush(82)
return
end subroutine spec9