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