2015-02-08 04:53:20 -05:00
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subroutine downsam9(id2,npts8,nsps8,newdat,nspsd,fpk,c2,nz2)
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!Downsample from id2() into c2() so as to yield nspsd samples per symbol,
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!mixing from fpk down to zero frequency. The downsample factor is 432.
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use, intrinsic :: iso_c_binding
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use FFTW3
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include 'constants.f90'
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2015-02-08 06:10:28 -05:00
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integer(C_SIZE_T) NMAX1
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2015-02-08 04:53:20 -05:00
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parameter (NMAX1=604800)
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type(C_PTR) :: plan !Pointers plan for big FFT
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integer*2 id2(0:8*npts8-1)
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real*4, pointer :: x1(:)
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complex c1(0:NMAX1/2)
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complex c2(0:1440-1)
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real s(5000)
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logical first
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common/patience/npatience,nthreads
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data first/.true./
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save plan,first,c1,s,x1
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nfft1=NMAX1 !Forward FFT length
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df1=12000.0/nfft1
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npts=8*npts8
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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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!$omp critical(fftw) ! serialize non thread-safe FFTW3 calls
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plan=fftwf_alloc_real(NMAX1)
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call c_f_pointer(plan,x1,[NMAX1])
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x1(0:NMAX1-1) => x1 !remap bounds
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call fftwf_plan_with_nthreads(nthreads)
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plan=fftwf_plan_dft_r2c_1d(nfft1,x1,c1,nflags)
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call fftwf_plan_with_nthreads(1)
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!$omp end critical(fftw)
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first=.false.
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endif
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if(newdat.eq.1) then
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fac=6.963e-6 !Why this weird constant?
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x1(0:npts-1)=fac*id2(0:npts-1)
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x1(npts:nfft1-1)=0. !Zero the rest of x1
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call timer('FFTbig9 ',0)
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call fftwf_execute_dft_r2c(plan,x1,c1)
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call timer('FFTbig9 ',1)
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nadd=int(1.0/df1)
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s=0.
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do i=1,5000
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j=int((i-1)/df1)
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do n=1,nadd
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j=j+1
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s(i)=s(i)+real(c1(j))**2 + aimag(c1(j))**2
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enddo
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enddo
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endif
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ndown=8*nsps8/nspsd !Downsample factor
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nfft2=nfft1/ndown !Backward FFT length
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nh2=nfft2/2
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nf=nint(fpk)
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i0=int(fpk/df1)
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nw=100
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ia=max(1,nf-nw)
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ib=min(5000,nf+nw)
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call pctile(s(ia),ib-ia+1,40,avenoise)
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fac=sqrt(1.0/avenoise)
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do i=0,nfft2-1
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j=i0+i
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if(i.gt.nh2) j=j-nfft2
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c2(i)=fac*c1(j)
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enddo
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call four2a(c2,nfft2,1,1,1) !FFT back to time domain
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nz2=8*npts8/ndown
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return
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end subroutine downsam9
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