mirror of https://github.com/saitohirga/WSJT-X.git
134 lines
3.8 KiB
Fortran
134 lines
3.8 KiB
Fortran
subroutine filbig(dd,nmax,f0,newdat,nfsample,xpol,c4a,c4b,n4)
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! Filter and downsample complex data stored in array dd(4,nmax).
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! Output is downsampled from 96000 Hz to 1375.125 Hz.
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parameter (MAXFFT1=5376000,MAXFFT2=77175)
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real*4 dd(4,nmax) !Input data
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complex ca(MAXFFT1),cb(MAXFFT1) !FFTs of input
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complex c4a(MAXFFT2),c4b(MAXFFT2) !Output data
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real*8 df
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real halfpulse(8) !Impulse response of filter (one sided)
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complex cfilt(MAXFFT2) !Filter (complex; imag = 0)
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real rfilt(MAXFFT2) !Filter (real)
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integer*8 plan1,plan2,plan3,plan4,plan5
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logical first,xpol
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include 'fftw3.f'
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common/cacb/ca,cb
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equivalence (rfilt,cfilt)
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data first/.true./,npatience/1/
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data halfpulse/114.97547150,36.57879257,-20.93789101, &
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5.89886379,1.59355187,-2.49138308,0.60910773,-0.04248129/
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save
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if(nmax.lt.0) go to 900
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nfft1=MAXFFT1
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nfft2=MAXFFT2
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if(nfsample.eq.95238) then
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nfft1=5120000
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nfft2=74088
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endif
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if(first) then
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nflags=FFTW_ESTIMATE
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if(npatience.eq.1) nflags=FFTW_ESTIMATE_PATIENT
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if(npatience.eq.2) nflags=FFTW_MEASURE
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if(npatience.eq.3) nflags=FFTW_PATIENT
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if(npatience.eq.4) nflags=FFTW_EXHAUSTIVE
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! Plan the FFTs just once
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call timer('FFTplans ',0)
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call sfftw_plan_dft_1d(plan1,nfft1,ca,ca,FFTW_BACKWARD,nflags)
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call sfftw_plan_dft_1d(plan2,nfft1,cb,cb,FFTW_BACKWARD,nflags)
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call sfftw_plan_dft_1d(plan3,nfft2,c4a,c4a,FFTW_FORWARD,nflags)
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call sfftw_plan_dft_1d(plan4,nfft2,c4b,c4b,FFTW_FORWARD,nflags)
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call sfftw_plan_dft_1d(plan5,nfft2,cfilt,cfilt,FFTW_BACKWARD,nflags)
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call timer('FFTplans ',1)
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! Convert impulse response to filter function
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do i=1,nfft2
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cfilt(i)=0.
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enddo
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fac=0.00625/nfft1
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cfilt(1)=fac*halfpulse(1)
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do i=2,8
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cfilt(i)=fac*halfpulse(i)
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cfilt(nfft2+2-i)=fac*halfpulse(i)
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enddo
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call timer('FFTfilt ',0)
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call sfftw_execute(plan5)
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call timer('FFTfilt ',1)
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base=cfilt(nfft2/2+1)
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do i=1,nfft2
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rfilt(i)=real(cfilt(i))-base
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enddo
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df=96000.d0/nfft1
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if(nfsample.eq.95238) df=95238.1d0/nfft1
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first=.false.
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endif
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! When new data comes along, we need to compute a new "big FFT"
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! If we just have a new f0, continue with the existing ca and cb.
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if(newdat.ne.0) then
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nz=min(nmax,nfft1)
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do i=1,nz
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ca(i)=cmplx(dd(1,i),dd(2,i))
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if(xpol) cb(i)=cmplx(dd(3,i),dd(4,i))
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enddo
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if(nmax.lt.nfft1) then
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do i=nmax+1,nfft1
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ca(i)=0.
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if(xpol) cb(i)=0.
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enddo
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endif
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call timer('FFTbig ',0)
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call sfftw_execute(plan1)
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if(xpol) call sfftw_execute(plan2)
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call timer('FFTbig ',1)
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newdat=0
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endif
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! NB: f0 is the frequency at which we want our filter centered.
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! i0 is the bin number in ca and cb closest to f0.
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i0=nint(f0/df) + 1
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nh=nfft2/2
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do i=1,nh !Copy data into c4a and c4b,
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j=i0+i-1 !and apply the filter function
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if(j.ge.1 .and. j.le.nfft1) then
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c4a(i)=rfilt(i)*ca(j)
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if(xpol) c4b(i)=rfilt(i)*cb(j)
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else
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c4a(i)=0.
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if(xpol) c4b(i)=0.
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endif
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enddo
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do i=nh+1,nfft2
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j=i0+i-1-nfft2
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if(j.lt.1) j=j+nfft1 !nfft1 was nfft2
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c4a(i)=rfilt(i)*ca(j)
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if(xpol) c4b(i)=rfilt(i)*cb(j)
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enddo
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! Do the short reverse transform, to go back to time domain.
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call timer('FFTsmall',0)
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call sfftw_execute(plan3)
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if(xpol) call sfftw_execute(plan4)
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call timer('FFTsmall',1)
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n4=min(nmax/64,nfft2)
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go to 999
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900 call sfftw_destroy_plan(plan1)
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call sfftw_destroy_plan(plan2)
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call sfftw_destroy_plan(plan3)
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call sfftw_destroy_plan(plan4)
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call sfftw_destroy_plan(plan5)
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999 return
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end subroutine filbig
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