WSJT-X/lib/fsk4hf/getfc2w.f90
Steven Franke a92e7508b9 wspr5d_exp now tries to detect sequences of 3, 6, and 9 bits.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7700 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-02 13:58:32 +00:00

83 lines
2.0 KiB
Fortran

subroutine getfc2w(c,csync,npeaks,fs,fc1,fpks)
include 'wsprlf_params.f90'
complex c(0:NZ-1) !Complex waveform
complex cs(0:NZ-1) !For computing spectrum
complex csync(0:NZ-1) !Sync symbols only, from cbb
real a(5)
real freqs(413),sp2(413),fpks(npeaks)
integer pkloc(1)
df=fs/NZ
baud=fs/NSPS
a(1)=-fc1
a(2:5)=0.
call twkfreq1(c,NZ,fs,a,cs) !Mix down by fc1
! Filter, square, then FFT to get refined carrier frequency fc2.
call four2a(cs,NZ,1,-1,1) !To freq domain
ia=nint(0.75*baud/df)
cs(ia:NZ-1-ia)=0. !Save only freqs around fc1
call four2a(cs,NZ,1,1,1) !Back to time domain
cs=cs/NZ
cs=cs*cs !Square the data
call four2a(cs,NZ,1,-1,1) !Compute squared spectrum
! Find two peaks separated by baud
pmax=0.
fc2=0.
ja=nint(0.3*baud/df)
k=1
do j=-ja,ja
f2=j*df
ia=nint((f2-0.5*baud)/df)
if(ia.lt.0) ia=ia+NZ
ib=nint((f2+0.5*baud)/df)
p=real(cs(ia))**2 + aimag(cs(ia))**2 + &
real(cs(ib))**2 + aimag(cs(ib))**2
if(p.gt.pmax) then
pmax=p
fc2=0.5*f2
endif
freqs(k)=0.5*f2
sp2(k)=p
k=k+1
! write(52,1200) f2,p,db(p)
!1200 format(f10.3,2f15.3)
enddo
do i=1,npeaks
pkloc=maxloc(sp2)
ipk=pkloc(1)
fpks(i)=freqs(ipk)
ipk0=max(1,ipk-1)
ipk1=min(413,ipk+1)
! ipk0=ipk
! ipk1=ipk
sp2(ipk0:ipk1)=0.0
!write(*,*) i,fpks(i),fc2
enddo
a(1)=-fc1
a(2:5)=0.
call twkfreq1(c,NZ,fs,a,cs) !Mix down by fc1
cs=cs*conjg(csync)
call four2a(cs,NZ,1,-1,1) !To freq domain
pmax=0.
do i=0,NZ-1
f=i*df
if(i.gt.NZ/2) f=(i-NZ)*df
p=real(cs(i))**2 + aimag(cs(i))**2
! write(51,3001) f,p,db(p)
!3001 format(f10.3,e12.3,f10.3)
if(p.gt.pmax) then
pmax=p
fc3=f
endif
enddo
return
end subroutine getfc2w