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96 lines
2.1 KiB
Fortran
96 lines
2.1 KiB
Fortran
subroutine sfox_remove_tone(c0,fsync)
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parameter (NMAX=15*12000)
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parameter (NFILT=8000)
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complex c0(NMAX)
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complex cwindow(15*12000)
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complex cref(NMAX)
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complex cfilt(NMAX)
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real window(-NFILT/2:NFILT/2)
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! real endcorrection(NFILT/2+1)
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real s(NMAX/4)
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integer ipk(1)
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logical first
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data first/.true./
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save cwindow,first,pi
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if(first) then
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pi=4.0*atan(1.0)
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fac=1.0/float(NMAX)
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sumw=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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sumw=sumw+window(j)
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enddo
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cwindow=0.
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cwindow(1:NFILT+1)=window/sumw
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cwindow=cshift(cwindow,NFILT/2+1)
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call four2a(cwindow,NMAX,1,-1,1)
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cwindow=cwindow*fac ! frequency domain smoothing filter
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first=.false.
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endif
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fsample=12000.0
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baud=fsample/1024.0
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df=fsample/NMAX
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fac=1.0/NMAX
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do it=1,1 ! Remove 1 tone, if present
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cfilt=fac*c0
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call four2a(cfilt,NMAX,1,-1,1) ! fourier transform of input data
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iz=NMAX/4
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do i=1,iz
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s(i)=real(cfilt(i))**2 + aimag(cfilt(i))**2
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enddo
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ia=nint((fsync-50.0)/df)
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ib=nint((fsync+1500.0+50.0)/df)
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ipk=maxloc(s(ia:ib))
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i0=ipk(1) + ia - 1
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nbaud=nint(baud/df)
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ia=i0-nbaud
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ib=i0+nbaud
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s0=0.0
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s1=0.0
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s2=0.0
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do i=ia,ib
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s0=s0+s(i)
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s1=s1+(i-i0)*s(i)
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enddo
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delta=s1/s0
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i0=nint(i0+delta)
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f2=i0*df
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ia=i0-nbaud
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ib=i0+nbaud
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do i=ia,ib
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s2=s2 + s(i)*(i-i0)**2
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enddo
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sigma=sqrt(s2/s0)*df
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! write(*,*) 'frequency, spectral width ',f2,sigma
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if(sigma .gt. 2.5) exit
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! write(*,*) 'remove_tone - frequency: ',f2
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dt=1.0/fsample
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do i=1, NMAX
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arg=2*pi*f2*i*dt
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cref(i)=cmplx(cos(arg),sin(arg))
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enddo
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cfilt=c0*conjg(cref) ! baseband to be filtered
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call four2a(cfilt,NMAX,1,-1,1)
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cfilt=cfilt*cwindow
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call four2a(cfilt,NMAX,1,1,1)
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nframe=50*3456
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do i=1,nframe
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cref(i)=cfilt(i)*cref(i)
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c0(i)=c0(i)-cref(i)
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enddo
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enddo
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return
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end subroutine sfox_remove_tone
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