117 lines
2.8 KiB
Fortran
117 lines
2.8 KiB
Fortran
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subroutine avecho(id2,ndop,nfrit,nqual,f1,xlevel,sigdb,snr,dfreq,width)
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integer TXLENGTH
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parameter (TXLENGTH=27648) !27*1024
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parameter (NFFT=32768,NH=NFFT/2)
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parameter (NZ=4096)
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integer*2 id2(34560) !Buffer for Rx data
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real sa(NZ) !Avg spectrum relative to initial Doppler echo freq
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real sb(NZ) !Avg spectrum with Dither and changing Doppler removed
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integer nsum !Number of integrations
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real dop0 !Doppler shift for initial integration (Hz)
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real dop !Doppler shift for current integration (Hz)
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real s(8192)
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real x(NFFT)
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integer ipkv(1)
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complex c(0:NH)
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equivalence (x,c),(ipk,ipkv)
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common/echocom/nclearave,nsum,blue(NZ),red(NZ)
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save dop0,sa,sb
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dop=ndop
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sq=0.
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do i=1,TXLENGTH
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x(i)=id2(i)
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sq=sq + x(i)*x(i)
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enddo
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xlevel=10.0*log10(sq/TXLENGTH)
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if(nclearave.ne.0) nsum=0
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if(nsum.eq.0) then
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dop0=dop !Remember the initial Doppler
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sa=0. !Clear the average arrays
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sb=0.
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endif
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x(TXLENGTH+1:)=0.
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x=x/TXLENGTH
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call four2a(x,NFFT,1,-1,0)
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df=12000.0/NFFT
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do i=1,8192 !Get spectrum 0 - 3 kHz
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s(i)=real(c(i))**2 + aimag(c(i))**2
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enddo
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fnominal=1500.0 !Nominal audio frequency w/o doppler or dither
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ia=nint((fnominal+dop0-nfrit)/df)
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ib=nint((f1+dop-nfrit)/df)
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if(ia.lt.600 .or. ib.lt.600) go to 900
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if(ia.gt.7590 .or. ib.gt.7590) go to 900
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nsum=nsum+1
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do i=1,NZ
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sa(i)=sa(i) + s(ia+i-2048) !Center at initial doppler freq
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sb(i)=sb(i) + s(ib+i-2048) !Center at expected echo freq
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enddo
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call pctile(sb,200,50,r0)
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call pctile(sb(1800),200,50,r1)
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sum=0.
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sq=0.
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do i=1,NZ
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y=r0 + (r1-r0)*(i-100.0)/1800.0
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blue(i)=sa(i)/y
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red(i)=sb(i)/y
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if(i.le.500 .or. i.ge.3597) then
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sum=sum+red(i)
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sq=sq + (red(i)-1.0)**2
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endif
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enddo
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ave=sum/1000.0
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rms=sqrt(sq/1000.0)
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redmax=maxval(red)
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ipkv=maxloc(red)
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fac=10.0/max(redmax,10.0)
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dfreq=(ipk-2048)*df
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snr=(redmax-ave)/rms
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sigdb=-99.0
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if(ave.gt.0.0) sigdb=10.0*log10(redmax/ave - 1.0) - 35.7
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nqual=0
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if(nsum.ge.2 .and. nsum.lt.4) nqual=(snr-4)/5
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if(nsum.ge.4 .and. nsum.lt.8) nqual=(snr-3)/4
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if(nsum.ge.8 .and. nsum.lt.12) nqual=(snr-3)/3
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if(nsum.ge.12) nqual=(snr-2.5)/2.5
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if(nqual.lt.0) nqual=0
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if(nqual.gt.10) nqual=10
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! Scale for plotting
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blue=fac*blue
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red=fac*red
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sum=0.
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do i=ipk,ipk+300
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if(i.gt.NZ) exit
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if(red(i).lt.1.0) exit
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sum=sum+(red(i)-1.0)
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enddo
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do i=ipk-1,ipk-300,-1
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if(i.lt.1) exit
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if(red(i).lt.1.0) exit
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sum=sum+(red(i)-1.0)
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enddo
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bins=sum/(red(ipk)-1.0)
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width=df*bins
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nsmo=max(0.0,0.25*bins)
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do i=1,nsmo
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call smo121(red,NZ)
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call smo121(blue,NZ)
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enddo
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900 return
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end subroutine avecho
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