mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-09-17 10:46:33 -04:00
a9623703b3
changes on the C++ side. Basically works except that Tx audio has incorrect DT and audio is truncated at the end. Also, command line decoding using JT9 is not as sensitive as decoding from within WSJT-X.
67 lines
1.6 KiB
Fortran
67 lines
1.6 KiB
Fortran
subroutine subtractft4(dd,itone,f0,dt)
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! Subtract an ft4 signal
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!
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! Measured signal : dd(t) = a(t)cos(2*pi*f0*t+theta(t))
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! Reference signal : cref(t) = exp( j*(2*pi*f0*t+phi(t)) )
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! Complex amp : cfilt(t) = LPF[ dd(t)*CONJG(cref(t)) ]
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! Subtract : dd(t) = dd(t) - 2*REAL{cref*cfilt}
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use timer_module, only: timer
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parameter (NMAX=21*3456,NSPS=576,NFFT=NMAX,NFILT=1400)
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parameter (NFRAME=(103+2)*NSPS)
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real*4 dd(NMAX), window(-NFILT/2:NFILT/2), xjunk
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complex cref,camp,cfilt,cw
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integer itone(103)
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logical first
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data first/.true./
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common/heap8/cref(NFRAME),camp(NMAX),cfilt(NMAX),cw(NMAX),xjunk(NFRAME)
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save first
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nstart=dt*12000+1-NSPS
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nsym=103
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fs=12000.0
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icmplx=1
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bt=1.0
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nss=NSPS
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call gen_ft4wave(itone,nsym,nss,fs,f0,cref,xjunk,icmplx,NFRAME)
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camp=0.
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do i=1,nframe
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id=nstart-1+i
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if(id.ge.1.and.id.le.NMAX) camp(i)=dd(id)*conjg(cref(i))
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enddo
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if(first) then
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! Create and normalize the filter
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pi=4.0*atan(1.0)
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fac=1.0/float(nfft)
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sum=0.0
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do j=-NFILT/2,NFILT/2
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window(j)=cos(pi*j/NFILT)**2
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sum=sum+window(j)
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enddo
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cw=0.
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cw(1:NFILT+1)=window/sum
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cw=cshift(cw,NFILT/2+1)
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call four2a(cw,nfft,1,-1,1)
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cw=cw*fac
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first=.false.
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endif
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cfilt=0.0
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cfilt(1:nframe)=camp(1:nframe)
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call four2a(cfilt,nfft,1,-1,1)
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cfilt(1:nfft)=cfilt(1:nfft)*cw(1:nfft)
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call four2a(cfilt,nfft,1,1,1)
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! Subtract the reconstructed signal
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do i=1,nframe
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j=nstart+i-1
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if(j.ge.1 .and. j.le.NMAX) dd(j)=dd(j)-2*REAL(cfilt(i)*cref(i))
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enddo
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return
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end subroutine subtractft4
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