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https://github.com/saitohirga/WSJT-X.git
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77 lines
1.9 KiB
Fortran
77 lines
1.9 KiB
Fortran
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subroutine wspr_downsample(id2,k)
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! Input:
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! id2 raw 16-bit integer data, 12000 Hz sample rate
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! k pointer to the most recent new data
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! Output (in common/c0com)
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! c0 complex data downsampled to 1500 Hz
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parameter (NMAX=120*12000) !Total sample intervals per 30 minutes
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parameter (NDMAX=120*1500) !Sample intervals at 1500 Hz rate
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parameter (NSMAX=1366) !Max length of saved spectra
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parameter (NFFT1=1024)
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parameter (MAXFFT3=32768)
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real*4 w3(MAXFFT3)
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real*4 x0(NFFT1),x1(NFFT1)
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real*4 x2(NFFT1+105)
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real*4 ssum(NSMAX)
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logical*1 lstrong(0:1023) !Should be (0:512)
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integer*2 id2(NMAX)
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complex c0
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common/c0com/c0(NDMAX)
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data rms/999.0/,k0/99999999/,nfft3z/0/,nsps/8192/,nbfo/1500/
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save
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nfft3=nsps/4
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jstep=nsps/16
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if(k.gt.NMAX) go to 999
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if(k.lt.nfft3) go to 999 !Wait for enough samples to start
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if(nfft3.ne.nfft3z) then
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pi=4.0*atan(1.0)
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do i=1,nfft3
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w3(i)=2.0*(sin(i*pi/nfft3))**2 !Window for nfft3
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enddo
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nfft3z=nfft3
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endif
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if(k.lt.k0) then
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ja=0
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ssum=0.
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k1=0
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k8=0
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x2=0.
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! if(ndiskdat.eq.0) then
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! id2(k+1:)=0
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! c0=0. !This is necessary to prevent "ghosts". Not sure why.
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! endif
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endif
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k0=k
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nzap=0
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nbslider=0
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sigmas=1.0*(10.0**(0.01*nbslider)) + 0.7
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peaklimit=sigmas*max(10.0,rms)
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px=0.
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nwindow=2
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kstep1=NFFT1
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if(nwindow.ne.0) kstep1=NFFT1/2
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fac=2.0/NFFT1
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nblks=(k-k1)/kstep1
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gain=1.0
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do nblk=1,nblks
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do i=1,NFFT1
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x0(i)=gain*id2(k1+i)
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enddo
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call timf2(x0,k,NFFT1,nwindow,nb,peaklimit,x1, &
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slimit,lstrong,px,nzap)
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! Mix at nbfo Hz, lowpass at +/-750 Hz, and downsample to 1500 Hz complex.
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call mixlpf(x1,nbfo,c0(k8+1))
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k1=k1+kstep1
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k8=k8+kstep1/8
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enddo
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999 return
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end subroutine wspr_downsample
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