mirror of https://github.com/saitohirga/WSJT-X.git
55 lines
1.2 KiB
Fortran
55 lines
1.2 KiB
Fortran
subroutine analytic(d,npts,nfft,c)
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! Convert real data to analytic signal
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parameter (NFFTMAX=1024*1024)
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real d(npts)
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real h(NFFTMAX/2)
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complex c(NFFTMAX)
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data nfft0/0/
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save nfft0,h
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df=12000.0/nfft
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nh=nfft/2
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if(nfft.ne.nfft0) then
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t=1.0/2000.0
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beta=0.6
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pi=4.0*atan(1.0)
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do i=1,nh+1
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ff=(i-1)*df
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f=ff-1500.0
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h(i)=0.
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if(abs(f).le.(1-beta)/(2*t)) h(i)=1.0
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if(abs(f).gt.(1-beta)/(2*t) .and. abs(f).le.(1+beta)/(2*t)) then
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h(i)=0.5*(1+cos((pi*t/beta )*(abs(f)-(1-beta)/(2*t))))
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endif
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h(i)=sqrt(h(i))
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enddo
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nfft0=nfft
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endif
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fac=2.0/nfft
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c(1:npts)=fac*d(1:npts)
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c(npts+1:nfft)=0.
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call four2a(c,nfft,1,-1,1) !Forward c2c FFT
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! do i=1,nh
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! f=(i-1)*df
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! s(i)=real(c(i))**2 + aimag(c(i))**2
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! write(12,3001) f,s(i),db(s(i))
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!3001 format(3f12.3)
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! enddo
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! ia=700.0/df
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! c(1:ia)=0.
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! ib=2300.0/df
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! c(ib:nfft)=0.
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c(1:nh+1)=h(1:nh+1)*c(1:nh+1)
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c(1)=0.5*c(1) !Half of DC term
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c(nh+2:nfft)=0. !Zero the negative frequencies
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call four2a(c,nfft,1,1,1) !Inverse c2c FFT
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return
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end subroutine analytic
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