28 lines
675 B
Fortran
28 lines
675 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 12000/24=500 Hz
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include 'wspr_fsk8_params.f90'
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integer*2 iwave(NMAX)
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complex c(0:NMAXD-1)
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complex c1(0:NMAXD-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,NMAXD/2
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c1(i)=cx(i0+i)
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c1(NMAXD-i)=cx(i0-i)
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enddo
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c=c1/NMAXD
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call four2a(c,NMAXD,1,1,1) !c2c FFT back to time domain
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return
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end subroutine wspr_fsk8_downsample
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