WSJT-X/lib/fsk4hf/getfc2w.f90

65 lines
1.7 KiB
Fortran
Raw Normal View History

subroutine getfc2w(c,csync,fs,fc1,fc2,fc3)
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)
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.
ic=nint(baud/df)
ja=nint(0.5*baud/df)
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
! write(52,1200) f2,p,db(p)
!1200 format(f10.3,2f15.3)
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