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git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7680 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
30 lines
727 B
Fortran
30 lines
727 B
Fortran
subroutine wspr_fsk8_downsample(iwave,c)
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! Input: i*2 data in iwave() at sample rate 12000 Hz
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! Output: Complex data in c(), sampled at 4=500 Hz
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include 'wspr_fsk8_params.f90'
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parameter (NMAX=240*12000,NFFTD=NMAX/24)
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integer*2 iwave(NMAX)
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complex c(0:NZ-1)
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complex c1(0:NFFTD-1)
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complex cx(0:NMAX/2)
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real x(NMAX)
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equivalence (x,cx)
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df=12000.0/NMAX
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x=iwave
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call four2a(x,NMAX,1,-1,0) !r2c FFT to freq domain
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i0=nint(1500.0/df)
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c1(0)=cx(i0)
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do i=1,NFFTD/2
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c1(i)=cx(i0+i)
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c1(NFFTD-i)=cx(i0-i)
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enddo
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c1=c1/NFFTD
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call four2a(c1,NFFTD,1,1,1) !c2c FFT back to time domain
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c=c1(0:NZ-1)
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return
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end subroutine wspr_fsk8_downsample
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