mirror of https://github.com/saitohirga/WSJT-X.git
85 lines
2.4 KiB
Fortran
85 lines
2.4 KiB
Fortran
subroutine symspec(id,nz,savg)
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C Compute spectra at four polarizations, using half-symbol steps.
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parameter (NFFT=32768)
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parameter (NSMAX=60*96000)
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integer*2 id(4,NSMAX)
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real savg(4,NFFT)
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complex cx(NFFT),cy(NFFT) ! pad to 32k with zeros
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complex z
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real*8 ts,hsym
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common/spcom/ip0,ss(4,322,NFFT),ss5(322,NFFT)
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fac=1.e-4
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hsym=2048.d0*96000.d0/11025.d0 !Samples per half symbol
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npts=hsym !Integral samples per half symbol
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nsteps=322 !Half symbols per transmission
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do ip=1,4
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do i=1,NFFT
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savg(ip,i)=0.
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enddo
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enddo
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ts=1.d0 - hsym
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do n=1,nsteps
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ts=ts+hsym !Update exact sample pointer
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i0=ts !Starting sample pointer
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do i=1,npts !Copy data to FFT arrays
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xr=fac*id(1,i0+i)
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xi=fac*id(2,i0+i)
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cx(i)=cmplx(xr,xi)
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yr=fac*id(3,i0+i)
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yi=fac*id(4,i0+i)
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cy(i)=cmplx(yr,yi)
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enddo
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do i=npts+1,NFFT !Pad to 32k with zeros
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cx(i)=0.
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cy(i)=0.
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enddo
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call four2a(cx,NFFT,1,1,1) !Do the FFTs
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call four2a(cy,NFFT,1,1,1)
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do i=1,NFFT !Save and accumulate power spectra
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sx=real(cx(i))**2 + aimag(cx(i))**2
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ss(1,n,i)=sx ! Pol = 0
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savg(1,i)=savg(1,i) + sx
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z=cx(i) + cy(i)
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s45=0.5*(real(z)**2 + aimag(z)**2)
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ss(2,n,i)=s45 ! Pol = 45
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savg(2,i)=savg(2,i) + s45
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sy=real(cy(i))**2 + aimag(cy(i))**2
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ss(3,n,i)=sy ! Pol = 90
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savg(3,i)=savg(3,i) + sy
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z=cx(i) - cy(i)
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s135=0.5*(real(z)**2 + aimag(z)**2)
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ss(4,n,i)=s135 ! Pol = 135
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savg(4,i)=savg(4,i) + s135
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z=cx(i)*conjg(cy(i))
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! Leif's formula:
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! ss5(n,i)=0.5*(sx+sy) + (real(z)**2 + aimag(z)**2 -
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! + sx*sy)/(sx+sy)
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! Leif's suggestion:
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! ss5(n,i)=max(sx,s45,sy,s135)
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! Linearly polarized component, from the Stokes parameters:
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q=sx - sy
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u=2.0*real(z)
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! v=2.0*aimag(z)
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ss5(n,i)=0.707*sqrt(q*q + u*u)
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enddo
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enddo
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return
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end
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