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Improved estimates of Doppler spread. Comment the code in write_ref().
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Joe Taylor
parent
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commit
7bd797c0e9
@ -811,88 +811,99 @@ contains
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end subroutine get_candidates_fst240
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end subroutine get_candidates_fst240
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subroutine write_ref(itone,iwave,nsps,nmax,ndown,hmod,i0,fc,fmid,w50)
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subroutine write_ref(itone,iwave,nsps,nmax,ndown,hmod,i0,fc,fmid,w50)
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complex cwave(nmax)
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complex, allocatable :: c(:)
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real,allocatable :: ss(:)
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integer itone(160)
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integer*2 iwave(nmax)
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integer hmod
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data ncall/0/
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save ncall
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ncall=ncall+1
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! On "plotspec" special request, compute Doppler spread for a decoded signal
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allocate(c(0:nmax-1))
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wave=0
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fsample=12000.0
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nsym=160
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call gen_fst240wave(itone,nsym,nsps,nmax,fsample,hmod,fc, &
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complex, allocatable :: cwave(:) !Reconstructed complex signal
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1,cwave,wave)
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complex, allocatable :: g(:) !Channel gain, g(t) in QEX paper
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cwave=cshift(cwave,-i0*ndown)
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real,allocatable :: ss(:) !Computed power spectrum of g(t)
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! do i=1,nmax
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integer itone(160) !Tones for this message
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! write(51,1000) i,iwave(i),cwave(i)
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integer*2 iwave(nmax) !Raw Rx data
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!1000 format(2i10,f12.6)
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integer hmod !Modulation index
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! enddo
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data ncall/0/
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save ncall
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fac=1.0/32768
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ncall=ncall+1
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c=fac*float(iwave)*conjg(cwave)
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nfft=2*nmax
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call four2a(c,nmax,1,-1,1) !Forward c2c FFT
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allocate(cwave(0:nmax-1))
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allocate(g(0:nfft-1))
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wave=0
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fsample=12000.0
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nsym=160
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call gen_fst240wave(itone,nsym,nsps,nmax,fsample,hmod,fc,1,cwave,wave)
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cwave=cshift(cwave,-i0*ndown)
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fac=1.0/32768
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g(0:nmax-1)=fac*float(iwave)*conjg(cwave)
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g(nmax:)=0.
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call four2a(g,nfft,1,-1,1) !Forward c2c FFT
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df=12000.0/nmax
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df=12000.0/nfft
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ia=1.0/df
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ia=1.0/df
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smax=0.
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smax=0.
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do i=-ia,ia
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do i=-ia,ia !Find smax in +/- 1 Hz around 0.
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j=i
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j=i
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if(j.lt.0) j=i+nmax
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if(j.lt.0) j=i+nfft
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s=real(c(j))**2 + aimag(c(j))**2
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s=real(g(j))**2 + aimag(g(j))**2
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smax=max(s,smax)
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smax=max(s,smax)
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enddo
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enddo
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ia=10.1/df
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allocate(ss(-ia:ia))
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ia=10.1/df
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sum1=0.
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allocate(ss(-ia:ia)) !Allocate space for +/- 10 Hz
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sum2=0.
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sum1=0.
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ns=0
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sum2=0.
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do i=-ia,ia
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ns=0
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j=i
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do i=-ia,ia
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if(j.lt.0) j=i+nmax
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j=i
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ss(i)=(real(c(j))**2 + aimag(c(j))**2)/smax
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if(j.lt.0) j=i+nfft
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f=i*df
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ss(i)=(real(g(j))**2 + aimag(g(j))**2)/smax
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if(f.ge.-4.0 .and. f.le.-2.0) then
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f=i*df
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sum1=sum1 + ss(i)
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if(f.ge.-4.0 .and. f.le.-2.0) then
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ns=ns+1
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sum1=sum1 + ss(i) !Power between -2 and -4 Hz
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else if(f.ge.2.0 .and. f.le.4.0) then
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ns=ns+1
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sum2=sum2 + ss(i)
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else if(f.ge.2.0 .and. f.le.4.0) then
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endif
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sum2=sum2 + ss(i) !Power between +2 and +4 Hz
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enddo
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endif
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avg=min(sum1/ns,sum2/ns)
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enddo
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avg=min(sum1/ns,sum2/ns) !Compute avg from smaller sum
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sum1=0.
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sum1=0.
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do i=-ia,ia
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do i=-ia,ia
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f=i*df
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f=i*df
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if(abs(f).le.1.0) sum1=sum1 + ss(i)-avg
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if(abs(f).le.1.0) sum1=sum1 + ss(i)-avg !Power in abs(f) < 1 Hz
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y=0.99*ss(i) + ncall-1
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enddo
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write(52,1010) f,y
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1010 format(f12.6,f12.6)
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enddo
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ia=nint(1.0/df)
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ia=nint(1.0/df) + 1
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sum2=0.0
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sum2=0.0
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i1=-999
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xi1=-999
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i2=-999
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xi2=-999
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i3=-999
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xi3=-999
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do i=-ia,ia
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sum2z=0.
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sum2=sum2 + ss(i)-avg
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do i=-ia,ia !Find freq range that has 50% of signal power
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if(sum2.ge.0.25*sum1 .and. i1.eq.-999) i1=i
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sum2=sum2 + ss(i)-avg
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if(sum2.ge.0.50*sum1 .and. i2.eq.-999) i2=i
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if(sum2.ge.0.25*sum1 .and. xi1.eq.-999.0) then
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if(sum2.ge.0.75*sum1) then
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xi1=i - 1 + (sum2-0.25*sum1)/(sum2-sum2z)
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i3=i
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endif
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exit
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if(sum2.ge.0.50*sum1 .and. xi2.eq.-999.0) then
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endif
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xi2=i - 1 + (sum2-0.50*sum1)/(sum2-sum2z)
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enddo
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endif
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fmid=i2*df
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if(sum2.ge.0.75*sum1) then
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w50=(i3-i1+1)*df
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xi3=i - 1 + (sum2-0.75*sum1)/(sum2-sum2z)
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exit
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return
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endif
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end subroutine write_ref
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sum2z=sum2
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enddo
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xdiff=sqrt(1.0+(xi3-xi1)**2) !Keep small values from fluctuating too widely
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w50=xdiff*df !Compute Doppler spread
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fmid=xi2*df !Frequency midpoint of signal powere
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do i=-ia,ia !Save the spectrum for plotting
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f=i*df
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y=0.99*ss(i+nint(xi2)) + ncall-1
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write(52,1010) f,y
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1010 format(f12.6,f12.6)
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enddo
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return
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end subroutine write_ref
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end module fst240_decode
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end module fst240_decode
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