mirror of https://github.com/saitohirga/WSJT-X.git
158 lines
4.2 KiB
Fortran
158 lines
4.2 KiB
Fortran
subroutine ftpeak65(dat,jz,istart,f0,flip,pr,nafc,ftrack)
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C Do the the JT65 "peakup" procedure in frequency and time; then
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C compute ftrack.
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parameter (NMAX=30*11025)
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parameter (NS=1024)
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real dat(jz)
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real pr(126)
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real ftrack(126)
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complex c2(NMAX/2)
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complex c3(NMAX/4)
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complex c4(NMAX/16)
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complex c5(NMAX/64)
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complex c6(NMAX/64)
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complex z
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real s(NMAX/64)
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real ccf(-128:128)
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real c(-50:50,8)
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real*8 pha,dpha,twopi,dt,fsyncset
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twopi=8*datan(1.d0)
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fsyncset=-300.d0
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dt=2.d0/11025.d0 !Input dt (WSJT has downsampled by 2)
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call fil651(dat,jz,c2,n2) !Filter and complex mix; rate 1/2
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dt=2.d0*dt !We're now downsampled by 4
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dpha=twopi*dt*(f0-fsyncset) !Put sync tone at fsyncset
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pha=0.
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do i=1,n2
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pha=pha+dpha
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c2(i)=c2(i) * cmplx(cos(pha),-sin(pha))
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enddo
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call fil652(c2,n2,c3,n3) !Low-pass at +/- 500 Hz; rate 1/2
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dt=2.d0*dt !Down by 8
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dpha=twopi*dt*fsyncset !Mix sync tone to f=0
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pha=0.
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do i=1,n3
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pha=pha+dpha
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c3(i)=c3(i) * cmplx(cos(pha),-sin(pha))
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enddo
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call fil653(c3,n3,c4,n4) !Low-pass at +/- 100 Hz; rate 1/4
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dt=4.d0*dt !Down by 32
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call fil653(c4,n4,c5,n5) !Low-pass at +/- 25 Hz; rate 1/4
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dt=4.d0*dt !Down by 128
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C Use f0 and istart (as found by sync65) and do CCFs against the
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C pr(126) array to get improved symbol synchronization.
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C NB: if istart is increased by 64, kpk will decrease by 1.
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k0=nint(istart/64.0 - 7.0)
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call symsync65(c5,n5,k0,s,flip,pr,16,kpk,ccf,smax)
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C Fix up the value of istart. (The -1 is empirical.)
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istart=istart + 64.0*(kpk-1.0)
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C OK, we have symbol synchronization. Now find peak ccf value as a
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C function of DF, for each group of 16 symbols.
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C What about using filter fil657?
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df=0.25*11025.0/4096.0 !Oversample to get accurate peak
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idfmax=50
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iz=n5-31
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do idf=-idfmax,idfmax
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dpha=twopi*idf*df*dt
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pha=0.
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do i=1,iz
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pha=pha+dpha
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c6(i)=c5(i) * cmplx(cos(pha),-sin(pha))
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enddo
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z=0.
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do i=1,32
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z=z + c6(i)
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enddo
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s(1)=real(z)*real(z) + aimag(z)*aimag(z)
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do i=33,n5
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z=z + c6(i) - c6(i-32)
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s(i-31)=real(z)*real(z) + aimag(z)*aimag(z)
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enddo
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do n=1,8
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ia=nint((n-1)*126.0/8.0 + 1.0)
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ib=ia+15
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sum=0.
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do i=ia,ib
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j=32*(i-1) + k0 + kpk
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if(j.ge.1 .and. j.le.iz) sum=sum + flip*pr(i)*s(j)
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enddo
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c(idf,n)=sum/smax
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enddo
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enddo
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C Get drift rate and compute ftrack.
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! call getfdot(c,nafc,ftrack)
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jmax=0
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if(nafc.eq.1) jmax=25
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ssmax=0.
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do j=-jmax,jmax
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do i=-25,25
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ss=0.
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xj=j/7.0
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do n=1,8
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k=nint(i+(n-4.5)*xj)
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ss=ss + c(k,n)
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enddo
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if(ss.gt.ssmax) then
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ssmax=ss
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ipk=i
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jpk=j
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endif
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enddo
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enddo
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df=0.25*11025.0/4096.0
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dfreq=ipk*df
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fdot=jpk*df*60.0/(0.875*46.8)
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do i=1,126
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ftrack(i)=dfreq + fdot*(46.8/60.0)*(i-63.5)/126.0
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enddo
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pha=0.
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i0=k0 + kpk + 2000
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do i=1,iz
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k=nint(63.5 + (i-i0)/32.0)
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if(k.lt.1) k=1
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if(k.gt.126) k=126
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dpha=twopi*dt*ftrack(k)
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pha=pha+dpha
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c6(i)=c5(i) * cmplx(cos(pha),-sin(pha))
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enddo
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z=0.
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do i=1,32
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z=z + c6(i)
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enddo
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s(1)=real(z)*real(z) + aimag(z)*aimag(z)
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do i=33,n5
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z=z + c6(i) - c6(i-32)
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s(i-31)=real(z)*real(z) + aimag(z)*aimag(z)
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enddo
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sum=0.
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do i=1,126
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j=32*(i-1)+k0+kpk
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if(j.ge.1 .and. j.le.iz) sum=sum + flip*pr(i)*s(j)
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enddo
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return
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end
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