WSJT-X/lib/symspec2.f90

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subroutine symspec2(c5,nz3,nsps8,nspsd,fsample,freq,drift,snrdb,schk, &
i1SoftSymbolsScrambled)
! Compute soft symbols from the final downsampled data
complex c5(0:4096-1)
complex z
integer*1 i1SoftSymbolsScrambled(207)
real aa(3)
real ss2(0:8,85)
real ss3(0:7,69)
include 'jt9sync.f90'
data scale/10.0/
aa(1)=-1500.0/nsps8
aa(2)=0.
aa(3)=0.
do i=0,8 !Loop over the 9 tones
if(i.ge.1) call twkfreq(c5,c5,nz3,fsample,aa)
m=0
k=-1
do j=1,85 !Loop over all symbols
z=0.
do n=1,nspsd !Sum over 16 samples
k=k+1
z=z+c5(k)
enddo
ss2(i,j)=real(z)**2 + aimag(z)**2 !Symbol speactra, data and sync
if(i.ge.1 .and. isync(j).eq.0) then
m=m+1
ss3(i-1,m)=ss2(i,j) !Symbol speactra, data only
endif
enddo
enddo
call chkss2(ss2,freq,drift,schk)
ss=0.
sig=0.
do j=1,69
smax=0.
do i=0,7
smax=max(smax,ss3(i,j))
ss=ss+ss3(i,j)
enddo
sig=sig+smax
ss=ss-smax
enddo
ave=ss/(69*7) !Baseline
call pctile(ss2,9*85,35,xmed)
ss3=ss3/ave
sig=sig/69. !Signal
t=max(1.0,sig - 1.0)
snrdb=db(t) - 61.3
m0=3
k=0
do j=1,69
smax=0.
do i=0,7
if(ss3(i,j).gt.smax) smax=ss3(i,j)
enddo
do m=m0-1,0,-1 !Get bit-wise soft symbols
if(m.eq.2) then
r1=max(ss3(4,j),ss3(5,j),ss3(6,j),ss3(7,j))
r0=max(ss3(0,j),ss3(1,j),ss3(2,j),ss3(3,j))
else if(m.eq.1) then
r1=max(ss3(2,j),ss3(3,j),ss3(4,j),ss3(5,j))
r0=max(ss3(0,j),ss3(1,j),ss3(6,j),ss3(7,j))
else
r1=max(ss3(1,j),ss3(2,j),ss3(4,j),ss3(7,j))
r0=max(ss3(0,j),ss3(3,j),ss3(5,j),ss3(6,j))
endif
k=k+1
i4=nint(scale*(r1-r0))
if(i4.lt.-127) i4=-127
if(i4.gt.127) i4=127
! i4=i4+128
! if(i4.le.127) i1SoftSymbolsScrambled(k)=i4
! if(i4.ge.128) i1SoftSymbolsScrambled(k)=i4-256
i1SoftSymbolsScrambled(k)=i4
enddo
enddo
return
end subroutine symspec2